Over the past 20 years, the interest in the biological chemistry of HNO has increased significantly due to the numerous beneficial pharmacological effects of its donors. Increased availability of various HNO donors was accompanied by great progress in the understanding of HNO chemistry and chemical biology. This review is focused on the chemistry of HNO, with emphasis on reaction kinetics and mechanisms in aqueous solutions.Azanone  is the protonated form of the product of one-electron reduction of nitric oxide ( Formallificance . Interesificance . This resulfide HS and azaazanone” or “hydridooxidonitrogen” (which name is based on additive nomenclature). The commonly used name is “nitroxyl.” It has also been used to describe azanone anion, NO− [which IUPAC recommended name is “oxidonitrate (1−)”]. The term “nitroxyl” may be misleading as aminoxyl radicals, of the general formula R2N-O•, are known as “nitroxyl radicals.” Therefore, the reader must be aware that a literature search with the keyword “nitroxyl” may yield references to aminoxyl radicals R2N-O•. In some of the scientific literature names “nitroso hydrogen,” “monomeric hyponitrous acid,” “nitrosyl hydride” or “hydrogen oxonitrate,” were also used. For the compliance with the IUPAC recommendations and to avoid ambiguity, we suggest the use of the name “azanone” for HNO and “azanone anion” for NO−.Prior to describing HNO chemistry, it is important to briefly discuss the recommended and the used nomenclature. The IUPAC recommended name of HNO is “N-O, the N-H bond length rN-H and the H-N-O angle θH-N-O. The qualitative discussion of the electronic structure of HNO has been given by N-O = 1.212 Å, rN-H = 1.063 Å, and θH-N-O = 108.6°. HNO structure and NO bond vibrational frequency υNO has been the subject of numerous theoretical studies . Deprot− a pKa value of 4.7 for HNO was reported in 1970 (Ka(1HNO/3NO−) value of 11.4  is recommended. Shafirovich and Lymar have also estimated the pKa values for other HNO acid-base equilibria: pKa(1HNO/1NO−) ∼ 23, pKa(3HNO/3NO−) = −1.8  = −1.8 , suggest•NO, due to its electronic structure, has very low value — Eea = 0.026 ± 0.005 eV  = −0.81 V, and practically outside of the biologically compatible range (•NO reduction leads to the formation of HNO. Taking into account the postulated pKa(1HNO/3NO−) value of 11.4, Lymar and co-workers, estimated standard redox potential for •NO/HNO redox pair to be equal to −0.14 V (E°(•NO/HNO) = −0.14 V, and E°’(•NO/HNO) = −0.55 V for pH 7) (E°(•NO/HNO) = 0.27 V, and E°’(•NO/HNO) = −0.14 V for pH 7, based on the computational reevaluation of HNO solvation free energy (2/O2•– redox couple), would suggest the feasibility of •NO reduction to HNO by a variety of cellular enzymatic redox centers. The •NO/HNO interconversion under physiological conditions has been recently discussed in detail (Electron affinity of 0.005 eV . •NO redle range . At physor pH 7) . Those ve energy . Such van detail , and is 2N2O2 (k1a = (8 ± 3) × 106 M−1s−1) (2N2O2 have been reported with pKa (H2N2O2/HN2O2−) = 7.0 and pKa (HN2O2−/N2O22–) = 10.9. Therefore, at physiological pH (pH > 7), H2N2O2 exists predominantly in its mono-deprotonated form (HN2O2−). This form is responsible for the instability of H2N2O2 in aqueous solutions and for the formation of N2O .It should be noted, that direct experimental determination of the chemical reactivity of HNO is hampered by its rapid dimerization to hyponitrous acid H M−1s−1) . This rain situ, e.g., with the use of radiation techniques  involving one-electron reduction of •NO by solvated electrons or by hydrogen atoms (H•), or photochemical techniques , including photolysis of alkaline aqueous solutions of trioxodinitrate . Below, the radiation chemistry of aqueous solutions of •NO and the laser flash photolysis of aqueous solutions of N2O32− will be described, as those methods greatly contributed to our understanding of azanone chemistry and to the determination of the rate constants of the reactions involved. Further development of such methodologies for rapid in situ formation of HNO/NO−and for monitoring their reactions may overcome current obstacles in the studies of HNO/NO−chemistry and result in improved knowledge of the azanone chemistry and its biological fates.Due to the instability of HNO in aqueous solutions, in chemical studies on HNO reactivity it is necessary to use HNO donors, that release HNO in a controlled manner, or produce azanone •NO leads to the formation of nitrite (NO2−) and N2O. The primary transient reactive species produced within approximately 10–8 s after the exposition of water to ionizing radiation are hydroxyl radical (•OH), hydrated electron (eaq−), and hydrogen atom (H•) [ONOO−]where kvi in the presence of azanone scavenger is expressed by 2 and the scavenger studied.−, or such reaction is outcompeted by the reaction between ONOO−and the boronate probe; 3) the scavenger does not react with or interferes with the detection of the product of oxidation of the boronic probe; and 4) the amount of HNO released is significantly lower than the amount of the scavenger and of O2 in the solution.The rate of ArOH formation r[donor]Comparis2− was determined to be equal to (5.0 ± 0.9) × 103 M−1s−1  results in the formation of molecular nitrogen (N2) and water (k23 = (4.0 ± 0.3) × 103 M−1s−1. Recent analysis of the competition between O2 and NH2OH for HNO using the boronate reporter for ONOO−, resulted in the rate constant equal to (2.1 ± 0.4) × 104 M−1s−1  × 106 M−1s−1, k25 = (1.2 ± 0.2) × 106 M−1s−1 and k26 = (2.2 ± 0.7) × 104 M−1s−1, for HS−, HSO3−, and S2O32−, respectively (2O32− (4 M−1s−1 (− and HNO (− to form HS2− and release NH2OH (−O3SSNHOH adduct (the product of 2O32− could result in the formation of NH2OH and S4O62− anion (2OH (2S shows that this reaction leads to the formation of hydrogen polysulfides (H2Sn) or sulfur S8, depending on the relative concentrations of H2S and HNO. The reactivity of HNO towards selected inorganic scavengers is summarized in The second-order rate constants were determined to be equal to: ectively . The rat  and the glutathione disulfide  NH2 are formed from a single transient intermediate, supporting the hypothesis of GSNHOH formation (2 is not observed with other reactive nitrogen species (RNS): •NO, nitrogen dioxide (•NO2), ONOO−, or N2O3, making GS(O)NH2 a unique and HNO-specific product. GS(O)NH2 was, therefore, used as a marker for HNO generation from several biologically-relevant pathways: thiol-mediated decomposition of S-nitrosothiols, peroxidase-dependent NH2OH and N-hydroxy-L-arginine oxidation (Exposure of reduced glutathione (GSH) to HNO was shown to lead to the formation of both the sulfinamide derivative (GS(O)NHe, GSSG) . Higher ormation . It has xidation .It has been long assumed that HNO-driven oxidative transformation of thiols to sulfinamides is irreversible. C-terminal cysteines the nature of HNO-derived modifications is highly affected by the C-terminal carboxylate   .2− and O2, it was concluded that the rate constant for the reaction of GSH with NO−/HNO is significantly higher than 1 × 105 M−1s−1 (N-acetyl cysteine (NAC) were determined to be equal to 2 × 106 M−1s−1 and 5 × 105 M−1s−1, respectively (6 M−1s−1 (2 for HNO (using boronate probes for ONOO−), yielded the following values of the rate constants in aqueous solutions at pH 7.4: cysteine (kCys = (4.5 ± 0.9) × 106 M−1s−1, pKa = 8.3), glutathione (kGSH = (3.1 ± 0.6) × 106 M−1s−1, pKa = 8.8), N-acetylcysteine (kNAC = (1.4 ± 0.3) × 106 M−1s−1, pKa = 9.5) and captopril (kCap = (6 ± 1) × 105 M−1s−1, pKa = 9.8)  is the active form reacting with HNO. The second order rate constants for HNO reaction with protein-bound thiols were also determined in that study for human and bovine serum albumins (pKa ∼ 8.5 for Cys34) (kHSA = (1.4 ± 0.4) × 106 M−1s−1, kBSA = (1.4 ± 0.3) × 106 M−1s−1). Such a high reactivity of thiols towards HNO, together with high concentrations of GSH and albumin in cells and plasma, respectively, suggest that thiols may be the potential targets of HNO in biological systems.Several groups studied the kinetics of the reaction of HNO with GSH. Based on the effect of GSH on the rate of Angeli’s salt decomposition in aqueous solution at pH 7.4 in the presence of NO5 M−1s−1 . In an iectively . The rat6 M−1s−1 . More rea = 9.8) . It was N-acetylcysteine, bovine serum albumin and human serum albumin was also recently reported (kobs) can be expressed as a function of pH, which depends on thiol pKa, and the rate constants of azanone reaction with RS− (kthiolate) and with RSH (kthiol) (−) is favored (kthiolate ∼ 107 M−1s−1) over reactions with the thiol . Such observation is consistent with the observed inverse correlation between the reaction rate constant and the pKa value of the thiol.The pH-dependent kinetics of HNO reactions with selected thiols–glutathione, reported . It was kthiol) :kobs=ktKa  and inc species .6H5SO2−), the decomposition product of Piloty’s acid, has been determined as kbenzenesulfinate = (4.4 ± 0.9) × 104 M−1s−1  would be expected to be the products of those reactions . The rat4 M−1s−1 .RSO2-+H2−, 2-ClPhSO2− and 2-CF3PhSO2−) were also determined and are equal to (5.0 ± 1.2) × 104 M−1s−1, (3.0 ± 0.7) × 104 M−1s−1 and (1.1 ± 0.2) × 104 M−1s−1, respectively (3 M−1s−1), the rate constant for the reaction between HNO and benzenesulfinate  is one order of magnitude higher.The rate constants of HNO reactions with 2-bromo-, 2-chloro- and 2-trifluoromethylbenzenesulfinates  was reported  with reported . It was S-diazeniumdiolate transient product has also been recently proposed for the reaction of thiols with •NO, resulting in the formation of HNO  × 104 M−1s−1 .C- and S-nitroso compounds resulting in the formation of phosphine oxides and aza-ylides (kGSH = 2 × 106 M−1s−1), the rate constant for the reaction of HNO with a water-soluble phosphine, trisphosphine trisodium salt, was estimated at 37°C and pH 7.4 to be equal to 9 × 105 M−1s−1  × 107 M−1s−1  were recently re-evaluated and the values determined at pH 7.4 and 25°C are equal to (3.0 ± 0.5) × 107 M−1s−1 . The val6 M−1s−1 .5 M−1s−1.In 2015 C-nucleophiles can act as efficient scavengers of HNO , 1,3-cyclohexanedione (C6H8O2), and 1,3-cycloheptanedione (C7H10O2) was studied and the obtained second order rate constants were equal to 2.8 × 102 M−1s−1, 2.2 × 103 M−1s−1 and 6.8 × 103 M−1s−1, respectively. This indicates that the reactivity of cyclic C-nucleophiles toward HNO significantly increases with an increase in their ring size -2,4-piperidinedione = 1.4 × 104 M−1s−1.The substitution of one or more carbon atoms in the ring of 1,3-cyclohexanedione with nitrogen resulted in an increase in ward HNO . In the k2-thiobarbituric acid = 8.2 × 102 M−1s−1 and kMeldrum’s acid = 8.7 × 102 M−1s−1.The reactivity of barbituric acid, 1,3-dimethylbarbituric acid, 2-thiobarbituric acid and Meldrum’s acid  towards azanone  was alsoThe reactivity of HNO towards different classes of organic nucleophiles has been summarized in •NO (E°’ (•NO/1HNO) = −0.16 V for pH 7) )  , it coul 0.256 V ), Cu,Zn- 0.403 V ), aminox 0.204 V ), TEMPOL 0.204 V ) and 3-c 0.102 V ) and nit 0.270 V ) and c-P 0.270 V ).c(Fe3+) with an excess of Angeli’s salt in phosphate buffer at pH 7.0 at 25°C leads to the formation of ferrocytochrome c (cyt c(Fe2+)) (c(Fe3+) reduction was nearly zero order in the concentration of cyt c(Fe3+) and first order in the concentration of HN2O3−, suggesting that the decomposition of Angeli’s salt was controlling the rate of the reaction, consistent with HNO acting as the reductant of cyt c (Fe3+) (c reduction at low [HN2O3−]0/[cyt c (Fe3+)]0 ratio was close to 50%.In 1988 it was reported that the treatment of cyt c(Fe2+)) . The inic (Fe3+) . The repc(Fe3+) reduction by HNO have been reported in the literature: k39 = 2 × 104 M−1s−1, (k39 = 4 × 104 M−1s−1 (c(Fe3+) in aqueous solutions of Angeli’s salt was not observed in the presence of O2 (c (Fe2+) is oxidized to cyt c(Fe3+) in aerated solutions of Angeli’s salt (− in the reaction of HNO and O2 (c(Fe2+) by ONOO−  or ONOO authors .cyt c. In an elegant kinetic study on the reactivity of nitroxides toward HNO with the use of EPR spectrometry, the reduction of cyclic stable aminoxyl radicals (RN-O•) by HNO to the corresponding hydroxylamines (RN-OH) (Other mild one-electron oxidants reported to oxidize HNO to  (RN-OH)  was repo (RN-OH) .RN-O• +• radicals have been determined with the use of the competition kinetics against the reference reaction of HNO with ferric myoglobin (MbFeIII). In the presence of HNO donor, MbFeIII undergoes reductive nitrosylation with the formation of relatively stable ferrous nitrosyl complex, MbFeIINO, which can be followed by UV-Vis absorption spectroscopy. Using kMbFe(III) = 8 × 105 M−1s−1 (kTEMPO = (1.4 ± 0.2) × 105 M−1s−1), TEMPOL (kTEMPOL = (1.4 ± 0.2) × 105 M−1s−1) and 3-carbamoyl-PROXYL (k3-CP = (4.3 ± 0.4) × 104 M−1s−1) (kTEMPOL = 8 × 104 M−1s−1) (kTEMPO = 6.3 × 104 M−1s−1) (k = (8 ± 2) × 104 M−1s−1)  × 104 M−1s−1) (The second-order rate constants of HNO reactions with RN-O5 M−1s−1  as a ref M−1s−1) . Those v M−1s−1)  and TEMP M−1s−1)  and a mo M−1s−1) . Nitroxi M−1s−1) . This pr M−1s−1) . The pro4 M−1s−1 , a value M−1s−1) . Due to •NO will react with HNO to form the N2O2•− radical anion , are widely used in redox biology studies as scavengers of •NO  of characteristic EPR spectrum and •NO2 (•NO are in the range (0.4–16) × 104 M−1s−1  = 8 × 105 M−1s−1 (kPTIO = kc-PTIO = (1.4 ± 0.2) × 105 M−1s−1. Independently, the kinetics of c-PTIO reaction with HNO was determined using NH2OH as a competing agent and the kC-PTIO/k23 ratio of 5.5 ± 0.9 was obtained (k23 = (4.0 ± 0.3) × 103 M−1s−1 (k23 = (2.1 ± 0.4) × 104 M−1s−1 (kC-PTIO = (2.2 ± 0.5) × 104 M−1s−1 (kC-PTIO = (1.2 ± 0.4) × 105 M−1s−1. It has been also shown, that •NO2 radicals formed in such a system can oxidize Angeli’s salt anion to transient radical product, that decomposes to NO2− and •NO (k43 = 7.7 × 106 M−1s−1)  .N2O32-+64− anion as a •NO2 radical scavenger (64− and Fe(CN)63− anions are in redox equilibrium with nitronyl nitroxide radicals and Fe(CN)63− anion is an oxidant of HNO. Based on the established competition, the kc-PTIO/k23 ratio of 1.7 ± 0.2 and k23 = (4.0 ± 0.3) × 103 M−1s−1 (k23 = (2.1 ± 0.4) × 104 M−1s−1 (kc-PTIO = (6.8 ± 1.3) × 103 M−1s−1 and 2 M−1s−1 (kC-PTIO = (3.6 ± 1.1) × 104 M−1s−1 and 3 M−1s−1 cavenger . Such a 3 M−1s−1  or k23 4 M−1s−1  one can 2 M−1s−1  or kC-P3 M−1s−1 .c (cyt c), soluble guanylate cyclase (sGC), and cytochromes P450 (CYP450) (II)O2) reacts with HNO forming ferric heme and possibly •NO and H2O2 (k44 = 1 × 107 M−1s−1 (•NO formed upon HNO oxidation reacts with another Mb (FeII)O2 molecule with rate constant k45 = 3–5 × 107 M−1s−1 producing ferric heme and NO3− (II)O2 (II)O2 and Hb(FeII)O2 convert HNO to •NO rapidly. It is worth to emphasize that in the literature an alternative mechanism for the heme (FeII)O2/HNO reaction was also proposed. In that mechanism, two ferric hemes, hydroxylamine and O2 are the final products (The reaction of HNO with heme-proteins has been studied extensively for nearly 40 years. Among the studied heme-enzymes are myoglobin (Mb), hemoglobin (Hb), horseradish peroxidase (HRP), catalase (cat), cytochrome (CYP450) . The reaand H2O2  (Doyle aand H2O2  and the 7 M−1s−1 . •NO fornd NO3−  (Doyle and NO3− . Identic− (II)O2 . Overallproducts .heme-FeII)) reacts with HNO forming coordination complex Mb (FeII)HNO (4 M−1s−1 (5 M−1s−1 (II) with HNO is followed by subsequent reaction of Mb (FeII)HNO with HNO yielding Mb (FeIII)NO, with the rate constant estimated as 1.67 × 104 M−1s−1 (II) is equal to ca. 2.0 × 105 M−1s−1 (5 M−1s−1 (Deoxymyoglobin (Mb (FeFeII)HNO . Origina4 M−1s−1 . The re-5 M−1s−1 . The rea4 M−1s−1  (Zapata 4 M−1s−1 . For deo5 M−1s−1 . For oth5 M−1s−1 .heme-FeII)NO and Hb(FeII)NO, respectively   .heme-FeThe rate constant of reductive nitrosylation of metHb is difficult to determine due to the side reaction of HNO with β-93 cysteines of hemoglobin . Nonethe5 M−1s−1 and 2 × 106 M−1s−1  with HNO results in the reduction of iron heme and the formation of •NO, as already discussed in Oxidation of HNO to NO) (The reaction of cyt O to NO) . It has O to NO) .•NO (II)HNO complex (II)NO. sGC(FeIII) is unreactive toward HNO or •NO. However, a contrary report was published, where the HNO-dependent activation of sGC was excluded (II)HNO and HNO that follows to the formation of sGC(FeII)NO (In the case of sGC there is no estimated rate constant for its reaction with HNO. Miller and coworkers proposed that activation of sGC proceeds directly through HNO and the ferrous heme reaction without conversion of HNO to •NO . The exp complex  but not excluded . That re(FeII)NO  is respo(FeII)NO .II(NO) complex similarly to other heme enzymes   .4 M−1s−1)   is in re M−1s−1)  indicatiThe kinetics of HNO reaction with other porphyrins containing iron and manganese were also studied and the appropriate rate constants are compiled in via the possible metal porphyrin-donor complex ) is an important example, since it occurs naturally and is an essential mammalian coenzyme. It was shown that aquacobalamin (H2O-Cbl+) and hydroxycobalamin (HO-Cbl) in the presence of Angeli’s salt are converted to the nitroxyl cobalamin (NO−-CoIIICbl) (2O-Cbl+ occurs and the complex was observed. The rate constant for the AS/H2O-Cbl+ reaction at acidic pH was determined to be 122.6 ± 5.3 M−1s−1 (2O-Cbl+ and Piloty’s acid (PA) has shown that PA also reacts directly with H2O-Cbl+ at neutral pH (28.4 ± 0.4 M−1s−1) (−-CoIIICbl)  . The mec3 M−1s−1 . Recent  M−1s−1) . In turn M−1s−1) . The mec M−1s−1) ; 2016. ToIIICbl) ; 2016.To summarize, the reaction scheme of HNO with heme-proteins is very complex and still remains an area that requires further studies and analyses. In addition, an interesting aspect relates to the direct reactions of HNO-donors with metal-porphyrins, of potential pharmacological relevance.2O3−, however the exact stoichiometry of this reaction with respect to HNO is unclear (c(Fe3+) (10–40 μM), the Cu,Zn-SOD-inhibitable reduction of cyt c(Fe3+) was observed. The Cu,Zn-SOD concentration was selected to be sufficient to compete with cyt c(Fe3+) for O2•–, but too low to detectably inhibit NADPH oxidation. That experiment strongly suggested the generation of O2•– in HNO/O2/NADPH system. The authors proposed that NADPH is oxidized in such a solution to NADP• radicals, which subsequently reduce O2 to O2•− with the formation of NADP+. At higher concentration (∼2 μM), Cu,Zn-SOD inhibited by ∼50% the oxidation of NADPH  × 104 M−1s−1 was reported (k52 = (1.3 ± 0.4) × 104 M−1s−1 was also determined for NADPH. In the direct reaction of HNO with NADH or NADPH in deaerated Angeli’s salt solution, one may expect the formation of hydroxylamine as an HNO reduction product  with Angeli’s salt in aerobic buffered aqueous solutions (pH 7.4) has been presented in several scientific reports (N-nitroso derivative as the main product. The yield of its formation is rather low (below 20%) and depends on the indolic compound: Angeli’s salt concentrations ratio (N-nitroso derivative is significantly higher in the presence of bicarbonate (N-nitrosation mechanism. The recent study of N-acetyl-L-tryptophan and small peptides containing either tryptophan or both tryptophan and cysteine residues, has shown that in the presence of cysteine, excess HNO is required for efficient TrpNO formation, clearly indicating, that tryptophan residues are significantly less reactive towards HNO, than cysteine residues.The results of the studies on the reaction of various indolic compounds (e.g.,  reports . All thens ratio . It was arbonate , which m•NO, and may be expected to exhibit unique physiological activity. The experimental limitations due to its instability under physiological conditions provide a significant hindrance in study design to further explore HNO chemistry. The development of new donors and rapid generation methods for time-resolved kinetic studies may overcome some of those obstacles. In addition, the combination of the experimental data with theoretical calculations may help with drawing reliable mechanistic conclusions. Finally, as a note of caution, it has to be emphasized that many rate constants of HNO reactions listed in this review were determined by competition kinetics, via kinetic simulations or other indirect approaches, and are based on very few values determined directly. Therefore, it can be expected that with the development of new experimental methods, the rate constants may need to be re-evaluated and the mechanistic conclusions adjusted.HNO show a different chemical reactivity than


The tetrel bond strength for the [I4C···X−] series and [I4Tt···X−] , was weak-to-moderate, whereas that in the remaining 16 complexes was dative tetrel bond type with very large interaction energies and short Tt···X close contact distances. The basis set superposition error corrected interaction energies calculated with the highest-level theory applied, [CCSD(T)/def2-TZVPPD], ranged from −3.0 to −112.2 kcal mol−1. The significant variation in interaction energies was realized as a result of different levels of tetrel bonding environment between the interacting partners at the equilibrium geometries of the complex systems. Although the ωB97X-D computed intermolecular geometries and interaction energies of a majority of the [I4Tt···X−] complexes were close to those predicted by the highest level of theory, the MP2 results were shown to be misleading for some of these systems. To provide insight into the nature of the intermolecular chemical bonding environment in the 25 molecule–anion complexes investigated, we discussed the charge-density-based topological and isosurface features that emanated from the application of the quantum theory of atoms in molecules and independent gradient model approaches, respectively.Twenty-five molecule–anion complex systems [I Ion–molecule interactions are fascinating in chemistry ,2,3,4, b−, Br−, or I−) attracts the electrophiles on bonded Si atoms in the neutral molecules. Neither anion is located precisely at the centroid of the neutral molecule(s). When the anion (Cl−) is entrapped inside the Si20 cage of a fully or partially chlorinated icosasilane molecular entity (20 cage to stabilize the tetrel-centered (Cl−)Si···Cl and/or (H−)Si···Cl close contacts.r entity e,f, its The fundamental phenomena that drive isolated neutral molecules to self-assemble with anions play a significant role in the processes of anion recognition and anion transport, among others ,17,18. O4, of the tetrel tetrahalide family (TtX4), where Tt stands for the elements in Group 14 of the periodic table and X represents the halide derivative . The anions considered were the halide derivative, X−. It is worth mentioning that the theoretical chemistry of 1:1 complexes formed of lighter members of the TtX4  family with the first three halide anions was recently reported  complexes be called ordinary tetrel bonds . Density functional theory  ,31,32,33 (QTAIM) ,41,42,43 (QTAIM) ,45-based (QTAIM) ,46 respo(ωB97X-D ) and ab  methods, in conjunction with the def2-TZVPPD basis set, were also employed to demonstrate the accuracy of MP2 and ωB97X-D geometries and energies of [I4Tt···X−]. Standard non-relativistic calculations were performed without considering the effect of spin-orbit coupling for heavy atoms such as Pb, following a previous study  level. An isoelectron density envelope of 0.001 a.u. was used on which to compute the potential, even though the use of higher isoelectron density envelopes was suggested in other studies for chemical systems containing low-polarizable atomic basins  are consistent with the topological charge-density-based features emanated using QTAIM. Both Multiwfn . The AIMAll code was used  and [ωB97X-D/def2-QZVPPD]. The best agreement between experiment and theory is observed with [ωB97X-D/def2-QZVPPD], and MP2 shows a tendency to underestimate r(Tt–I). A very similar trend was obtained with these methods in conjunction with the def2-QZVPPD basis set.Crystals of TtIe (ICSD) ,78,79,804. From these, it may be seen that the atomic basins are connected to each other in each isolated monomer through bond paths (solid lines between atomic basins in atom color) that pass-through bond critical points (tiny green spheres), thus recovering the expected tetrahedral Td shape of TtI4.b is larger at the C–I bcps in CI4 than at the Pb–I bcps in PbI4. It follows the trend across the series: ρb (C–I) > ρb (Si–I) > ρb (Ge–I) > ρb (Sn–I) > ρb (Pb–I). The trend signifies that the charge concentration is predominant at the C–I bcps in CI4 relative to that at the Pb–I bcps in PbI4.The charge density ρb, b is stabilizing (Hb < 0) at the Tt–I bcps, which is due to the potential energy density Vb that dominates over the gradient kinetic energy density Gb at the bcp. Hb is increasingly more positive at the Tt–I bcps across the series from CI4 through SiI4 to GeI4 to SnI4 to PbI4. This is consistent with the character of Tt–I bonds in TtI4, in which it progressively becomes less covalent than ionic, passing from CI4 through SiI4 to PbI4. That is, the covalency of the Tt–I bond follows this order: C–I > Si–I > Ge–I > Sn–I > Pb–I. Furthermore, the sign of ∇2ρb at Tt–I bcps is also negative for all monomers except for the Tt–I  bcps, giving an indication that the Tt–I bonds in CI4, SiI4, and GeI4 are relatively more covalent than those in SnI4 and PbI4. Typically, ∇2ρb < 0 and Hb < 0 represent covalent (shared-type) interactions; ∇2ρb > 0 and Hb > 0 represent ionic (closed-shell) interactions; and ∇2ρb > 0 and Hb < 0 represents mixed  interactions  complexes. They are shown in The five halide anions have linearly approached the Tt atom from the opposite side of the I–Tt covalent bond in TtI4 with the five halide anions. Because the σ-hole on the carbon atom in CI4 is the weakest compared to that on the Tt atom in TtI4   , the strC···At−] , respect4C···X−] increases as the halogen derivative becomes more polarizable; it is smallest in [I4C···F−], with r(Tt···F) = 2.665 Å with [CCSD/def2-TZVPPD]. By contrast, the I–C–I angle in complexed [I4C···F−] either increases or decreases compared to that of its uncomplexed counterpart (∠I–C–I = 109.47°). For instance, the I–C bond linearly attached to the anion forms smaller ∠I–C–I with the three nearest-neighbor I atoms, whereas the remaining I–C bonds that are not directly involved in the formation of tetrel bond are associated with larger ∠I–C–I. These two angles types are 107.5 (111.3°), 108.1 (110.8°), 108.4 (110.5), 108.8 (110.1°), and 108.8 (110.1°) in [I4C···F−], [I4C···Cl−], [I4C···Br−], [I4C···I−], and [I4C···At−], respectively.The C···X intermolecular distance in [I4C···F−], 4C···F−]. The latter ones mimic the I···X  links in the other four members of the same family , a feature that has been recommended for identifying hydrogen bonds [4C···F−], [I4C···Cl−], [I4C···Br−], [I4C···I−], and [I4C···At−] are ca. 2.871, 3.626, 3.892, 4.274, and 4.322 Å, respectively. The former three are less than their respective sum of vdW radii of 3.50 (I + F), 3.86 (I + Cl), and 3.90 Å (I + Br), whereas the latter two are slightly greater than the sum of their respective sum of vdW radii of 4.08 (I + I) and 4.04 Å (I + At). . Since rom ref. ,62,97,99re known ,101, whi4C···X−], as CCSD. However, the increase in the size of the basis set from def2-TZVPPD to def2-QZVPPD has resulted in a slight increase in the Tt···X intermolecular distance with ωB97X-D and MP2. Whatever is the size of the basis set, the intermolecular distances predicted using MP2 are underestimated relative to ωB97X-D and CCSD. Furthermore, [MP2/def2-TZVPPD] has predicted the C···I and C···At bond distances to be 4.091 and 4.083 Å for [I4C···I−] and [I4C···At−], respectively; they were 3.990 and 4.009 Å with def2-QZVPPD, respectively. This means that MP2 does not correctly predict the trend in C···I and C···At bonding distances, as predicted by ωB97X-D and CCSD  and Hb (Hb < 0) at the bcps of the three equivalent bonds, were equivalent  > [I4C···Cl−] (δ = 0.030) > [I4C···Br−] (δ = 0.023) > [I4C···I−] (δ = 0.019) > [I4C···At−] (δ = 0.017), in consistent with the trend found for interaction energy  is completely lost.The nature of the intermolecular bonding environment found in  c–e. Simil, or Br a–c, but Ge···X−] d,e. This4Si···Br−], in which, the responsible interacting units were involved in the formation of a dative tetrel bond; it is in a manner similar to that found for [I4Si···X−] . On the other hand, MP2 has recognized the attraction between I4Si and X− in the first four members of the [I4Si···X−] series to be unusually strong and that in [I4Si···At−] to be moderate. The former result with MP2 is applicable to the [I4Ge···X−] series as well. This means that the Tt···X close contacts in the above-mentioned molecule–anion systems are not ordinary tetrel bonds; they are dative tetrel bonds.While the bonding features noted above were obtained from [ωB97X-D/def2-QZVPPD], the [CCSD/def2-QZVPPD] method has predicted an exception for [Ib is appreciable at the Ge···X bcps in [I4Ge···X−] when X points to F, Cl, and Br. For [I4Ge···I−], the ρb is small at Ge···I bcp (ρb = 0.0048 a.u.), and the interaction between the monomers is also reinforced by I···I interactions  bcps in [I4Ge···X−] are not only typical for coordinate bonds but larger than that can be expected for ordinary non-covalent interactions such as hydrogen bonds, and halogen bonds, among others (ρb < 0.05 a.u.). They may be comparable with the ρb values of the Tt–I coordinate bonds in isolated and complexed TtI4. A similar conclusion might be arrived at for Si···X bcps in [I4Si···X−] , Our QTAIM analysis, ractions d. The ρb2ρb (∇2ρb > 0) and Hb (Hb < 0), 4Si···X−] provided [CCSD/def2-TZVPPD] results are considered. The large δ values corresponding to atom–atom pairs responsible for the Si···X and Ge···X  close contacts provide further evidence that there are no π-type interactions involved; they are purely σ-type coordinate dative bonds. By contrast, the δ values are very small for atom–atom pairs causing the Si···X and Si···X close contacts in [I4Ge···X−] and [I4Ge···X−] , respectively, indicative of closed-shell interactions. The three equivalent I···X halogen···halogen close contacts in each of [I4Ge···X−] and [I4Ge···X−]  are described by small δ values, and positive ∇2ρb and Hb. Similarly, the Si···X and Ge···X  tetrel bonds are described by small δ values, as expected.From the sign and magnitude of ∇4 and PbI4, respectively, are stronger than those of TtI4 . Therefore, their acidic strengths are adequate enough to recognize the five halide anions when in close proximity. This may be rationalized from QTAIM’s molecular graphs of resulting configurations, [I4Sn···X−] and [I4Pb···X−] , illustrated in 4 and PbI4. This means that the TtI4 molecule is structurally fully deformed in the presence of each of the five halide anions. There is no secondary intermolecular interaction that can play a role in the geometrical stability of the resulting complex anions, as found for other series (see above). In all cases, the tetrel center adopts a trigonal bipyramidal geometry . Clearly, the resulting complex anions each is nothing but a coordination compound, and the Tt···X close-contact is formally a Tt–X dative tetrel bond. In such cases, charge transfer from the anion to the σ*(I–Tt) anti-bonding orbital is expected, and the SN2 mechanism is likely to play a role in driving the dative bond formation between the interacting species [The σ-holes on Sn and Pb in SnI species .4Pb···X−] series and the smallest for the [I4C···X−] series. In particular, the [ωB97X-D/def2-QZVPPD] level QTAIM charge transfer from X− to PbI4 is 0.263, 0.371, 0.424, 0.515 and 0.588 e for [I4Pb···F−], [I4Pb···Cl−], [I4Pb···Br−], [I4Pb···I−], and [I4Pb···At−], respectively. The corresponding charge transfer values were 0.229, 0.334, 0.382, 0.460, and 0.519 e for [I4Sn···F−], [I4Sn···Cl−], [I4Sn···Br−], [I4Sn···I−], and [I4Sn···At−], respectively. These results imply that the nature of charge-transfer in the Sn- and Pb-based anions is virtually similar and that the charge-transfer preference is consistent with the interaction energy preference across a given series, indicating that the charge-transfer phenomenon is likely to be one of the most prominent contributors to the interaction. Our calculation suggests that the extent of charge transfer is the largest for the [Ie calculated for [I4C···F−], [I4C···Cl−], [I4C···Br−], [I4C···I−], and [I4C···At−], respectively. These results may lead to a conclusion that the formation of stronger complexes accompanies an appreciable amount transfer of charge between the interacting monomers, and is not very surprising   is non-negligible; it may be comparable to that of the Tt–I bcps of complexed I4Tt. The Tt–I and Tt···X bcps are both characterized by ∇2ρb > 0 and Hb < 0, indicating the presence of a mixed covalent and ionic character. Since Hb becomes increasingly more positive at the Tt···X bcp passing from [I4Tt···F−] through [I4Tt···Cl−] to [I4Tt···Cl−] to [I4Tt···Br−] to [I4Tt···I−] to [I4Tt···At−], it is clear that these interactions are less covalent in the same order. The ∇2ρb values are decreasing in the series from [I4Tt···F−] through [I4Tt···Cl−] to [I4Tt···At−], indicating that the Tt···F tetrel bond is more ionic than the Tt···At tetrel bond. In the case of Tt = Si and Ge, the Tt···X  bcps show ∇2ρb > 0 and Hb < 0  bond in the respective system. The characteristics of Si–I bonds in I4Si resemble the C–I bonds in I4C.From the molecular graphs of QTAIM in d Hb < 0 . The fou4Tt···X−]  is considerably larger than what were calculated for ordinary tetrel bonds  upon its attractive engagement with the halide anions. For comparison, we note that the δ values for Tt–I and Tt···X coordinate and dative tetrel bonds in [I4Tt···X−] are smaller than, and comparable to, those reported for metal–C(O) coordinate bonds ; however, those of Tt···X ordinary tetrel bonds are comparable with what were reported for metal···metal  interactions  in [M2(CO)10] and [M3(μ-H)3(CO)12]  complexes  (Tt = C). The I···X closed contacts in several of these systems appeared at larger IGM-interδg isovalues (Top). On the other hand, the Tt···X close contacts showed up at lower IGM-interδg isovalues (Bottom). This is not very surprising since smaller isolvalues are typically necessary for the physical appearances of isosurfaces corresponding to weakly bonded interactions. By contrast, the relatively stronger interactions can be traceable with larger isovalues since charge density around the critical bonding region is generally appreciable. The bluish isosurface originated with large IGM-interδg isovalues for [I4C···F−] indicates that the attraction between the interacting units is very prominent . The view is also transferable to the [I4Ge···X−] systems (not shown).The [I4Sn···X−] and [I4Pb···X−] , the IGM-interδg isosurfaces were visualizable with an isovalue close to 0.055 a.u. 4Pb···X−] series. Passing from the left to the right of 4Tt···F−] through [I4Tt···Cl−] to [I4Tt···Br−] to [I4Tt···I−] to [I4Tt···At−] .In the case of [I4C···X−] series and [I4Tt···X−] , the int (BSSE)E values for all other molecule–anion systems are much larger than the so-called covalent limit for hydrogen bonds  [4Tt···X−], it is clear that the complex stability is largely determined by the polarizability of the Tt atom in I4Tt and the halogen derivative. These energies calculated in the range from −3.0 to −112.2 kcal mol−1 with [CCSD(T)/def2-TZVPPD], −1 < int (BSSE)E < −5.0 kcal mol−1), moderate E < −10.0 kcal mol−1), strong E < −25.0 kcal mol−1), very strong E ≤ −40.0 kcal mol−1), and ultra-strong (int (BSSE)E >> −40.0 kcal mol−1 . At the highest level of theory applied, [CCSD(T)/def2-TZVPPD], the weakest and strongest of the [I4Tt···X−] systems are found to be [I4C···At−] (int (BSSE)E = −3.20 kcal mol−1) and [I4Si···F−] (int (BSSE)E = −112.15 kcal mol−1), respectively.Except for the  with def2-TZVPPD and def2-QZVPPD, respectively; these are indicative of the fact that the strength of the tetrel bond between Si of I4Si and Br− is moderate. As mentioned already above, this is not the case with MP2 since the intE (BSSE) for the same system, for instance, with def2-QZVPPD, is predicted to be −60.0 kcal mol−1; the large intE (BSSE) implies that the attraction between I4Si and Br− causes the formation of Si–Br dative tetrel bond. This result is consistent with [CCSD(T)/def2-TZVPPD], which has predicted an intE (BSSE) of −53.16 kcal mol−1 for the same system. Second, the [ωB97X-D/def2-TZVPPD] level intE (BSSE) values for the remaining four systems of the [I4Si···X]− series are in qualitative and quantitative agreement with [CCSD(T)/def2-TZVPPD]. MP2, however, unusually overestimated the interaction energies for [I4Si···I−] and [I4Si···At−]. The discrepancy between the DFT (or CCSD(T)) and MP2 energies is likely due to the latter method’s misleading prediction of the Si···I and Si···At close contacts, thus pushing the interacting atoms in [I4Si···I−] to be bonded with each other via a dative tetrel bond. These peculiar results indicate that applying the MP2 approach to predict the correct nature of the tetrel bond in molecule–anion complex systems formed by heavier tetrel derivatives in molecular entities should be exercised with caution.From int(BSSE),E between the five members of each series [I4Tt···X]− follows the trend: [I4Tt···F−] > [I4Tt···Cl−] > [I4Tt···Br−] > [I4Tt···I−] > [I4Tt···At−] . Note that changing the basis set from def2-TZVPPD to def2-QZVPPD somehow restored the [CCSD(T)/def2-TZVPPD] level energy preference at the ωB97X-D level (but not at the MP2 level) when Tt = C, but not when Tt = Pb. One reason for the anomalous change in the preference of energy ordering between [I4Tt···I−] and [I4Tt···At−] is that the post-HF MP2 method greatly overestimates the BSSE, as well as the electron-electron correlation energy, relative to the DFT and CCSD(T). On the other hand, the CCSD(T) method has properly accounted for electron-electron correlation energy, which ensured the correct preference of stabilization energies among the five members of any given series, [I4Tt···X−].The preference of BSSE-corrected interaction energy, t···At−] . This isint(BSSE)E on the distance of separation r(Tt···X) for 25 molecule–anion complexes, [I4Tt···X−], obtained using ωB97X-D, MP2 and CCSD(T). Regardless of the different calculation methods utilized, the dependence was found to be quadratic. The square of the regression coefficient R2 was moderately higher (R2 = 0.9325) for ωB97X-D compared to CCSD(T) and lower (R2 = 0.8923) for MP2.−1, from 2.60 to 13.58 kcal mol−1, and from 1.42 to 13.44 kcal mol−1, respectively. However, when using the def2-QZVPPD basis set, the BSSE in energy has decreased sharply, giving rise to values in the range from 0.02 to 0.13 kcal mol−1 with ωB97X-D and from 1.01 to 5.01 kcal mol−1 with MP2. CCSD(T) with def2-QZVPPD was computationally very expensive; no conclusions could be drawn about the range of BSSE in energy with this method. int(BSSE)E and intE, obtained using [ωB97X-D/def2-QZVPPD], [MP2/def2-QZVPPD] and [CCSD(T)/def2-TZVPPD], respectively, showing a perfect linear dependence at the former level than that at the latter two. We note further that the BSSE in energy is minimal with DFT but larger with MP2 and CCSD(T). It is very large with the def2-TZVPPD basis set than with the def2-QZVPPD basis set. For example, for ωB97X-D, MP2, and CCSD(T) with def2-TZVPPD, the BSSE in energy ranged from 0.05 to 9.68 kcal mol4Tt···X−]  was theoretically investigated to clarify the nature of the selectivity of the I4Tt host for five guest  anions. The MP2 geometries and interaction energies for the 25 molecule–anion systems were underestimated and overestimated, respectively, relative to DFT and CCSD methods, and in some cases, the MP2 results were unreliable. The chemical bonding features obtained using DFT were consistent with the computationally expensive CCSD and CCSD(T) results, with an exception for [I4Si···Br−]. For the latter, the tetrel bonding characteristics predicted by CCSD could not be reproduced by DFT-ωB97X-D. Similarly, the significant overestimation of the interaction energy of [I4Si···I−] with MP2 was in sharp disagreement with that computed using ωB97X-D and CCSD(T).In this study, the series    systems, except for [I4C···X−]  and [I4Si···X−] . This was the case with [ωB97X-D/def2-TZVPPD] and [ωB97X-D/def2-QZVPPD], but [I4Ge···At−] was added to the exclusion list. The result was different from [MP2/def2-QZVPPD] in that it predicted exceptions only for [I4C···X−] , and is not surprising given it is an MP2’s tendency to underestimate intermolecular distances. Although these latter two computational methods exclude intermolecular interactions in systems that do not follow the stringent “less than the sum of vdW radii rule,” the exclusion was also consistent with the nature of bond path topology revealed using QTAIM. For example, for [I4C···X−] , [I4Tt···X−]  and [I4Tt···X−] , no QTAIM-based bond path topology exists between Tt and X at the [ωB97X-D/def2-QZVPPD] level. This means that QTAIM does not recognize the existence of Tt···X tetrel bonding in the host–guest systems when the tetrel bond distance between Tt and X exceeds the sum of the vdW radii of Tt and X, even though this type of limitation of QTAIM has been attributed to the arbitrary nature of the space partitioning scheme. Even so, it should be borne in mind that the Tt and X atoms of the interacting monomers in all complex systems were indeed tetrel bonded to each other, evidenced by the IGM-interδg-based isosurfaces.The Tt···X separation distance calculated by [CCSD/def2-TZVPPD] was smaller than the vdW radii of the Tt and X atoms for all [I


The molecular packing is consolidated by van der Waals interactions between these ribbons.The whole molecule of the title compound is generated by twofold rotational symmetry. In the crystal, molecules are linked by intermolecular C—H⋯O interactions with  22H19NO2, is generated by twofold rotational symmetry. The N atom exhibits a trigonal-planar geometry and is located on the twofold rotation axis. In the crystal, molecules are linked by C—H⋯O contacts with R22(12) ring motifs, and C—H⋯π interactions, resulting in ribbons along the c-axis direction. van der Waals interactions between these ribbons consolidate the molecular packing. Hirshfeld surface analysis indicates that the greatest contributions to the crystal packing are from H⋯H (45.5%), C⋯H/H⋯C (38.2%) and O⋯H/H⋯O (16.0%) interactions.The whole molecule of the title compound, C The phenyl ring (C1–C4/C2A/C3A) attached to the N1 atom and the phenyl rings (C7–C12 and C7A–C12A) of the two symmetry-related 1-phenylethan-1-one groups are oriented at 89.65 (6)° to each other.The asymmetric unit of the title compound contains half a molecule, the complete molecule being generated by the twofold rotational axis. Atoms N1, C1 and C4 are located on the twofold rotation axis Fig. 1. The N1 3.A⋯O1 to 1.2546 (blue) a.u  reveal that H⋯H (45.5%), C⋯H/H⋯C (38.2%) and O⋯H/H⋯O (16.0%) interactions make the greatest contributions to the surface contacts. N⋯H/H⋯N (0.3%) contacts also contribute to the overall crystal packing of the title compound. The Hirshfeld surface analysis confirms the importance of H-atom contacts in establishing the packing. The large number of H⋯H, C⋯H/H⋯C and O⋯H/H⋯O interactions suggest that van der Waals interactions and hydrogen bonding play the major roles in the crystal packing sulfonyl]-N-phenylbenzenesulfonamide bis(pyridine-2-carboxamide) bis(3-phenylacrylate) [XEBWUY (III); Sabari et al., 2012I) possesses twofold rotational symmetry. The N atom has a trigonal-planar geometry and is located on the twofold rotation axis. Weak C—H⋯O hydrogen bonds connect the molecules, forming a three-dimensional network. The asymmetric unit of (II) contains two independent molecules with similar conformations. In the crystal, N—H⋯O and weak C—H⋯O hydrogen bonds link the molecules into a three-dimensional supramolecular structure. Weak intermolecular C—H⋯π interactions are also observed. In (III), the C=C double bonds adopt an E configuration. In the crystal, pairs of C—H⋯O hydrogen bonds link the molecules into inversion dimers.A search of the Cambridge Structural Database  = 1.2Ueq(C). Owing to poor agreement between observed and calculated intensities, eighteen outliers  were omitted during the final refinement cycle.Crystal data, data collection and structure refinement details are summarized in Table 210.1107/S2056989022005382/tx2050sup1.cifCrystal structure: contains datablock(s) I. DOI: 10.1107/S2056989022005382/tx2050Isup2.hklStructure factors: contains datablock(s) I. DOI: 2173928CCDC reference:  crystallographic information; 3D view; checkCIF reportAdditional supporting information:


In the crystal, the molecules are cross-linked via intermolecular C—H⋯N hydrogen bonds and C—H⋯π interactions into a three-dimensional network.In the title compound, the molecule adopts an  33H33N3, is a carbazolophane, which is a cyclophane composed of two carbazole fragments. It has a planar chirality but crystallizes as a racemate in the space group Panti-configuration, in which two carbazole fragments are partially overlapped. Both carbazole ring systems are slightly bent, with the C atoms at 3-positions showing the largest deviations from the mean planes. The dihedral angle between two carbazole fragments is 5.19 (3)°, allowing an intramolecular slipped π–π interaction [Cg⋯Cg = 3.2514 (8) Å]. In the crystal, the molecules are linked via intermolecular C—H⋯N hydrogen bonds and C—H⋯π interactions into a network sheet parallel to the ab plane. The molecules of different sheets form other C—H⋯π interactions, thus forming a three-dimensional network.The title compound, C Previously, our group reported the EPR spectrum of the title compound, but no other chemical properties were examined because of the very low yield  Å for the N1/C4–C15 ring system and 0.062 (1)Å for N2/C16–C27 ring system. In both carbazole fragments, the C atoms at the 3-positions bridged through the dimethyleneamino group show the largest deviations from the mean planes [0.1177 (14) Å for C7 and −0.1082 (14) Å for C19]. The dihedral angle formed by two carbazole fragments is 5.19 (3)°, providing an intramolecular slipped parallel π–π interaction . In comparison, in the related PO compounds, the dihedral angles between two carbazole fragments and the centroid–centroid distances are 5.96 (6)° and 3.294 (4) Å for N-cyanamide-bridged [3.3]carbazolophane carbazolophane °, smaller than those in the related compounds , that is, the hybridization of N3 atom is closer to sp3 than to sp2, reflecting the difference in the resonance effect of the substituent at the N3 atom.The title compound has a planar chirality but crystallizes as a racemate in the centrosymmetric space group 3.C(9) chain motif running parallel to the b axis. The molecules are further joined into columns along the a-axis direction by pairs of C—H⋯π interactions , forming a centrosymmetric dimer  forms another centrosymmetric dimer -10,11,22,23-tetrahydro-9H,21H-5,8:15,12-bis(metheno)triazacyclohexadecino-diindole carbazolophane, YUKYEL; Tani et al., 2020anti-3-cyano-3-aza-1,3-dicarbazolacyclooctaphane carbazolophane, BACKOG; Tani et al., 2001N-cyanamide-bridged FO [3.3]carbazolophane, syn-3-cyano-3-aza-1,3-dicarbazolacyclooctaphane benzene clathrate  Å for the benzene rings bridged by cyanamide, 3.447 (2) Å for the central pyrrole rings and 3.792 (3) Å for the outer benzene rings. Three of the remaining four structures are PO [m.n]carbazolophanes; anti-ethenylene and 1,3-xylylene-bridged [2.5]carbazolophane carbazolophane carbazolophane ° and 3.8062 (15) Å for ethenylene and 1,3-xylylene-bridged [2.5]carbazolophane; 15.04 (9)° and 3.732 (3) Å for cyanamide-bridged [3.4]carbazolophane; 24.87 (11)° and 3.901 (3) Å  for oxa-bridged [3.5]carbazolophane. The last of the seven compounds is a FO carbazolophane, syn-cyclobutane-bridged [2.4]carbazolophane  in dichloromethane (150 mL) and sodium hydroxide  in water (10 mL). Then, the flask was filled with argon and was stirred at room temperature for 3 d. The reaction mixtures were washed with water, then dried over anhydrous sodium sulfate. Solvent was removed under reduced pressure, and the residue was purified by silica gel chromatography . Elution from hexane:ethyl acetate (19:1) gave a white solid . Elution from hexane:ethyl acetate (10:1) gave mixtures including a syn-configuration (FO isomer), but they were difficult to separate. A part of the title compound was recrystallized from dichloromethane:ethanol (1:3) to give a colorless crystal suitable for X-ray diffraction. Melting point: 482–484 K. 1H NMR  δ = 1.08 , 1.57–1.60 ,1.78 , 2.81–2.97 , 3.74–3.90 , 4.10–4.17 , 5.34 , 6.38 , 7.25-7.30 , 7.46–7.53 , 7.67 , 8.11 .A solution of 9,9′-bis[3-(bromomethyl)-96.Uiso(H) = 1.2Ueq(C).Crystal data, data collection and structure refinement details are summarized in Table 210.1107/S2056989022003383/yk2167sup1.cifCrystal structure: contains datablock(s) global, I. DOI: 10.1107/S2056989022003383/yk2167Isup2.hklStructure factors: contains datablock(s) I. DOI: 2161895CCDC reference:  crystallographic information; 3D view; checkCIF reportAdditional supporting information:


IIIS2N2O2 chromophore contains two O,N,S-donating dianionic ligands in perpendicular planes, with the O and S atoms in cis and the N atoms in trans positions. The FeIII ion is in the high-spin state at 100 K. The variable-temperature magnetic susceptibility measurements (5–320 K) are consistent with the presence of a high-spin S = 5/2 FeIII ion.The Fe 3)2NH2][Fe(C10H11O2N3S)2], are reported. The asymmetric unit consists of an octahedral [FeIII(L)2]− fragment, where L2− is 3-ethoxysalicylaldehyde thiosemicarbazonate(2−), and a dimethylammonium cation. Each L2− ligand binds with the thiolate S, the imine N and the phenolate O atoms as donors, resulting in an FeIIIS2N2O2 chromophore. The ligands are orientated in two perpendicular planes, with the O and S atoms in cis positions, and mutually trans N atoms. The FeIII ion is in the high-spin state at 100 K. The variable-temperature magnetic susceptibility measurements (5–320 K) are consistent with the presence of a high-spin FeIII ion with D = 0.83 (1) cm−1 and g = 2.The synthesis and crystal structure (100 K) of the title compound, [(CH IR spectroscopic measurements of (I)−1 were carried out at room temperature using an ATR  PerkinElmer FT–IR Frontier spectrometer.A room-temperature IR spectrum of 3-ethoxysalicylaldehyde thiosemicarbazone within the range 4000–400 cm1H and 13C NMR spectra were recorded in DMSO-d6 (dimethyl sulfoxide) using a Bruker cryomagnet BZH 300/52 spectrometer (300 MHz), with the recorded chemical shifts in δ (in parts per million) relative to an internal standard of tetramethylsilane (TMS).M, versus temperature, T, were conducted between 5 and 320 K, heating and cooling at a rate of 2 K min−1 in an applied field, μ0H, of 0.1 T using a Quantum Design MPMS-5S superconducting quantum interference device (SQUID) magnetometer. The SQUID magnetometer was calibrated using a standard palladium sample. The background due to the sample holder and the diamagnetic signal of the sample, estimated using Pascal’s constants  magnetic susceptibility, χ2-3-OEt-thsa) was carried out according to the general procedure described by Yemeli Tido : δ (ppm) 11.39 , 9.02 , 8.40 , 7.90–8.13 , 6.72–7.50 , 4.05 , 1.35 . 13C NMR : δ (ppm) 182.8 (C=S), 147.4, 146.7 (C—O), 140.1 (C=N), 119.5, 118.7, 114.5 (C aromatic), 64.6 (C—N), 74.0 (O—CH2), 15.1 (O—C—CH3). IR : 3400 (νOH), 3169 (νNH), 3249 (νNH2), 2935 (νCH3), 2896 (νCH2), 1618 (νC=N), 1535–1600 (νC=C), 1270 (νC—N), 1167 (νC=S).The synthesis of 3-ethoxysalicylaldehyde thiosemicarbazone (HTido 2010 (yield: 3)2NH2][Fe(3-OEt-thsa)2], (I)3)3·9H2O  was dissolved in water (10 ml). The ligand H2-3-OEt-thsa  was dissolved in methanol (60 ml) with the addition of dimethylamine, 40 wt% in water . To this mixture, the FeIII salt solution was added dropwise with constant stirring. The resulting dark-green solution was stirred and heated to 80 °C for approximately 10 min. The solution was then allowed to stand at room temperature until crystals had formed. The dark-green microcrystals were isolated by filtration and dried . IR : 3436, 3414 (νNH), 3265, 3098 (νNH2), 3012 (νCH3), 2971 (νCH2), 1614, 1586 (νC=N), 1570–1541 (νC=C ring), 1238 (νC—O), 1215 (νN—N), 1078 (νC—N), 736 (νC—S).The synthesis of ferrate(III), (I)P21/n, with Z = 4. The asymmetric unit consists of one formula unit, [(CH3)2NH2][Fe(3-OEt-thsa)2], with no atom on a special position. The FeIII cation is coordinated by the thiolate S, phenolate O and imine N atoms of each of the two dianionic O,N,S-tridentate L2− ligands. The donor atoms of the ligands are situated in two perpendicular planes, with the O and S atoms in cis positions, and mutually trans N atoms. Selected geometric parameters are listed in Table 2The structure of dimethylammonium bis compound at 103 (and 298 K)  confirm that the FeIII cation can be related to the bond angles of the FeO2N2S2 coordination core. An analysis of the bond angles involving the opposite ligand donor atoms at 100 K is very enlightening, as it shows that the octahedral geometry of the present high-spin FeIII compound, with O1—Fe1—S1 = 158.48 (5)°, O101—Fe1—S101 = 158.89 (5)° and N1—Fe1—N101 = 167.63 (7)°, is considerably less regular than that of the low-spin compound Cs[Fe(3-OEt-thsa-Me)2]·CH3OH, with the bond angles S11—Fe—O11 = 177.83 (14)°, S21—Fe—O21 = 178.01 (13)° and N11—Fe—N21 = 178.9 (2)° ° and O101—Fe—N101 = 84.03 (7)°] than the five-membered chelate ring [S1—Fe—N1 = 78.45 (5)° and S101—Fe—N101 = 78.93 (5)°]. The r.m.s. deviations from their least-squares plane of atoms of the six-membered chelate ring of both coordinated ligands are 0.197 and 0.177 Å for Fe1/N11/C17/C11/C12/O11 and Fe1/N101/C107/C101/C102/O101, respectively, and the corresponding values for the five-membered chelate rings are 0.129 and 0.102 Å for Fe1/N11/C12/C18/S11 and Fe1/N101/C102/C108/S101, respectively. It appears that the metal chelate rings deviate slightly from the ideal planar structure. Furthermore, the O—Fe—N and S—Fe—N bite angles of the six- and five-membered chelates are deficient by ca 38 and 30°, respectively, compared to the angle at the vertex of a regular hexagon (120°) or pentagon (108°), respectively. In comparison to other (cation+)[Fe(L2−)2]·x(solvent) compounds of related ligands  compounds contain FeIII in the low-spin state, whereas the present compound contains FeIII in the high-spin state. Consequently, (I) displays longer FeIII–donor atom bond lengths, which are associated with more restricted bite angles. Moreover, the remaining bond angles involving each six-membered chelate ring  or the thiolate S (S1 and S101) atoms. The charge of the two g Table 2 are, as III complex is further enhanced by the high degree of electron delocalization throughout the chelated ligands, which is evident from the geometric parameters. The C—S, C—N and N—N bond lengths of (I)i.e. single bond) and 2 (i.e. double bond). The C8—S1 bond length of 1.746 (3) Å and the C108—S101 bond length of 1.752 (2) Å suggest partial electron delocalization of these C—S bonds. This feature has also been found in the structure of the related high-spin FeIII compound Cs[Fe(thsa)2] at 103 K  at 100 K of 1.301 (3) and 1.301 (3) Å, respectively, which correspond to the C—N bond lengths of 1.314 (10) and 1.303 (11) Å, respectively, for Cs[Fe(thsa)2] at 103 K OLEX2 versus temperature measurements for (I)III ion. The data collected on heating and cooling coincide over the temperature range studied. The temperature dependence of χMT collected on cooling between 320 and 5 K is displayed in Fig. 3MT is temperature independent with a value of 4.41 (1) cm3 K mol−1 [5.94 (1) µB/Fe]. This is just above the expected value of 4.38 cm3 K mol−1 (5.92 µB/Fe) for FeIII in its high-spin (S = 5/2) state with an electronic g factor of 2. χM−1(T) is linear in T and a fit to a Curie–Weiss law between 100 and 320 K shown in Fig. 4B/Fe.Magnetic susceptibility MT drops rapidly below 100 K. This may be due to weak (antiferro)magnetic interactions between neighbouring spins or may reflect a splitting of the S = 5/2 state  term HCEF = D[zS2 − S(S + 1)/3] + E(xS2 – yS2), with D and E being the axial and rhombic zero-field splitting, respectively. The 6S high-spin state is split into three Kramers doublets. For E = 0, the doublets are separated by 2D and 6D from the lowest energy doublet. The Zeeman energy zH = gμBzHS and the molar susceptibility with a field along z isX = D/kBT, NA is Avogadro’s number and kB is the Boltzmann constant  cm−1 with g = 2. D is in the range expected for high-spin FeIII  spectroscopy.χ al. 2002, but theIII compounds that have so far been reported to contain the 3-ethoxysalicylaldehyde 4-R′-thiosemicarbazonate(2−) dianion. In Cs[Fe(3-OEt-thsa-Me)2]·CH3OH 2NH2][Fe(3-OEt-thsa)2] compound, (I)R′ substituent on the terminal N atom of the thiosemicarbazide moiety, as (I) contains a H atom, whereas Cs[Fe(3-OEt-thsa-Me)2]·CH3OH 2NH2+versus Cs+; and (iii) the presence of a methanol solvent molecule in the crystal lattice of Cs[Fe(3-OEt-thsa-Me)2]·CH3OH , whereas Cs[Fe(3-OEt-thsa-Me)2]·CH3OH forms intermolecular hydrogen-bonded ring systems which link neighbouring FeIII entities. These factors determine the arrangement of the FeIII entities within the unit cell, which is further characterized by the space group P21/n, with Z = 4 and V = 2576.35 (17) Å3 for (I), with a volume of 644.09 Å3 per high-spin FeIII formula unit, and the space group PZ = 2 and V = 1369.5 (8) Å3 for Cs[Fe(3-OEt-thsa-Me)2]·CH3OH, with a volume of 684.75 Å3 per low-spin FeIII formula unit [Fe(L2−)2]·x(solvent) materials and allows for a variation of the spin state of FeIII, with some members displaying temperature-dependent spin-crossover behaviour  I, global. DOI: 10.1107/S2053229622011597/jx3075Isup2.hklStructure factors: contains datablock(s) I. DOI: 2223775CCDC reference:


C(8) chains along the [100] direction. C—Br⋯π interactions connect these chains into parallel layers to (002). van der Waals interactions between the layers aid in the cohesion of the crystal packing.C—H⋯Br interactions connect molecules in the crystal, resulting in zigzag  14H8Br3N3O2, consists of three almost planar groups: the central dibromoethenyldiazene fragment and two attached aromatic rings. The mean planes of these rings form dihedral angles with the plane of the central fragment of 26.35 (15) and 72.57 (14)° for bromine- and nitro-substituted rings, respectively. In the crystal, C—H⋯Br interactions connect molecules, generating zigzag C(8) chains along the [100] direction. These chains are linked by C—Br⋯π interactions into layers parallel to (001). van der Waals interactions between the layers aid in the cohesion of the crystal packing. The most substantial contributions to crystal packing, according to a Hirshfeld surface analysis, are from Br⋯H/H⋯Br (20.9%), C⋯H/H⋯C (15.2%), O⋯H/H⋯O (12.6%) and H⋯H (11.7%) contacts.The molecule of the title compound, C The crystal packing is consolidated by C—F⋯π contacts and π–π stacking interactions, and short Br⋯O [2.9828 (13) Å] distances are also observed. In the crystal of (III), the molecules are linked into inversion dimers via short halogen–halogen contacts  compared to the van der Waals radius sum of 3.50 Å for two chlorine atoms. No other directional contacts could be identified, and the shortest aromatic ring centroid separation is greater than 5.25 Å. In the crystals of (IV) and (V), the molecules are linked through weak X⋯Cl contacts [X = Cl for (IV) and Br for (V)], C—H⋯Cl and C—Cl⋯π interactions into sheets lying parallel to (001). In the crystal of (VI), the molecules are stacked in columns parallel to [100] via weak C—H⋯Cl hydrogen bonds and face-to-face π–π stacking interactions. The crystal packing is further consolidated by short Cl⋯Cl contacts. In (VII), molecules are linked by C—H⋯O hydrogen bonds into zigzag chains running parallel to [001]. The crystal packing also features C—Cl⋯π, C—F⋯π and N—O⋯π interactions. In (VIII), C—H⋯N and short Cl⋯Cl contacts are observed, and in (IX), C—H⋯N and C—H⋯O hydrogen bonds and short Cl⋯O contacts occur.In -1-(4-bromophenyl)-2-(4-nitrobenzylidene)hydrazine (1 mmol), tetramethylethylenediamine , CuCl  and CBr4 (4.5 mmol). After 1-3 h , the reaction mixture was poured into 0.01 M solution of HCl , and extracted with dichloromethane (3 × 20 mL). The combined organic phase was washed with water (3 × 50 mL), brine (30 mL), dried over anhydrous Na2SO4 and concentrated in vacuo using a rotary evaporator. The residue was purified by column chromatography on silica gel using appropriate mixtures of hexane and dichloromethane (3/1–1/1). Crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution. Red solid (58%); m.p. 398 K. Analysis calculated for C14H8Br3N3O2 (M = 489.95): C 34.32, H 1.65, N 8.58; found: C 34.27, H 1.70, N 8.56%. 1H NMR  δ 8.16–7.41 . 13C NMR  δ 150.89, 149.62, 148.26, 136.43, 132.25, 127.77, 125.57, 124.53, 123.57, 93.24. ESI–MS: m/z: 490.96 [M + H]+.This dye was synthesized according to the reported method (Akkurt 6.Uiso(H) = 1.2Ueq(C). One reflection (110), affected by the beam stop, was omitted in the final cycles of refinement.Crystal data, data collection and structure refinement details are summarized in Table 310.1107/S205698902200620X/yk2170sup1.cifCrystal structure: contains datablock(s) I. DOI: 10.1107/S205698902200620X/yk2170Isup2.hklStructure factors: contains datablock(s) I. DOI: Click here for additional data file.10.1107/S205698902200620X/yk2170Isup3.cmlSupporting information file. DOI: 2178832CCDC reference:  crystallographic information; 3D view; checkCIF reportAdditional supporting information:


The synthesis and structures of dinuclear palladium complexes with 1,3-benzimidazolidine-2-thione and 1,3-imidazoline-2-thione are reported. H-benzimidazole-2-thiolato)-κ2N3:S;κ2S:N3-bis[cyanido(triphenylphosphine-κP)palladium(II)], [Pd2(C7H5N2S)2(CN)2(C18H15P)2] or [Pd22(CN)2(PPh3)2] (1), and bis(μ-1H-imidazole-2-thiolato)-κ2N3:S;κ2S:N3-bis[cyanido(triphenylphosphine-κP)palladium(II)] acetonitrile 0.58-solvate, [Pd2(C3H3N2S)2(CN)2(C18H15P)2]·0.58C2H3N or [Pd22(CN)2(PPh3)2]·0.58C2H3N (2). The compound [Pd22(CN)2(PPh3)2] is located on a crystallographic twofold axis while [Pd22(CN)2(PPh3)2]. 0.58(C2H3N) contains two partially occupied acetonitrile solvent molecules with occupancies of 0.25 and 0.33. In both of these compounds, the anionic bzimtH− and imtH− ligands coordinate through N,S-donor atoms in a bridging mode, covering four coordination sites of two metal centers and other two sites are occupied by two PPh3 ligand molecules. Finally, the remaining two sites of two metal centers are occupied by cyano groups, abstracted by the metals from the solvent during reaction. In the packing of the 1,3-benzimidazolidine- 2-thione and 1,3-imidazoline-2-thione complexes, there are intramolecular π–π interactions involving the thione moiety as well as an N—H⋯N hydrogen bond linking the thione and cyano ligands. In addition, in 2, as well as the π–π interaction involving the thione moieties, there is an additional π–π interaction involving one of the thione moieties and an adjacent phenyl ring from the triphenylphosphine ligand. There are also C—H⋯N interactions between the imidazoline rings and the acetonitrile N atoms.The synthesis and structures of dinuclear palladium complexes with 1,3-benzimidazolidine-2-thione (bzimtH) and 1,3-imidazoline-2-thione (imtH) are reported, namely, bis(μ-1 However, the X-ray crystal structure of the product revealed the formation of the unexpected dinuclear compound [Pd22(CN)2(PPh3)2] (1). Another thio-ligand, imtH2 yielded a similar dinuclear compound, [Pd22-(CN)2(PPh3)2] (2). In both these compounds, the anionic bzimtH− and imtH− ligands coordinate through N,S donor atoms in a bridging mode, covering four coordination sites of two metal centers, and other two sites are occupied by two PPh3 ligand molecules. Finally, the remaining two sites of two metal centers are occupied by cyano groups, abstracted by the metals from the solvent during reaction.The reaction of PdCl1 crystallizes in the monoclinic space group C2/c, and compound 2 in the monoclinic space group, P21/c. Selected bond distances and bond angles are given in Tables 11 is shown in Fig. 12 is shown in Fig. 21, here only half of the molecule is unique as the molecule lies on a crystallographic twofold axis. In 1, the Pd metal atom is bonded to one P, one S, one N and one C atoms with the respective bond distances as follows: Pd—P = 2.2861 (6), Pd—S = 2.3547 (6), Pd—N = 2.0545 (17), and Pd—C = 1.959 (2) Å. The trans bond angles, P—Pd—S and N—Pd—C, of 172.26 (2) and 178.31 (8)°, as well as the cis bond angles in the range 84.93 (6)–94.24 (5)°, reveal the distorted square-planar geometry of each metal center. One of the major factors in the conformation adopted by the molecule is the strong π–π interaction between the thione moieties , as seen in Fig. 1Cg⋯Cg = 3.3560 (9) Å with a slippage of 1.408 Å].Compound 2 is similar to that of 1. Nevertheless, there are minor differences in the bond distances and angles pertaining to the two metal centers of compound 2 , 2.3541 (5), 2.0345 (17) and 1.957 (2) Å , and 2.2984 (5), 2.3542 (5), 2.0345 (17) and 1.943 (2) Å . For both metal centers, the trans bond angles [P—Pd—S and N—Pd—C = 173.86 (2)–179.31 (8)°] and the adjacent bond angles [86.54 (7)– 92.80 (4)°] are similar to those of compound 1. These bond angles again reveal the distorted square-planar geometry of each metal center of compound 2. The various bond distances described above are normal and none unusual. Compound 1 has carbon–sulfur (C—S) bond distance of 1.728 (2), while in compound 2 it is 1.734 (2) Å. These distances are in between single (1.81 Å) and double-bond (1.68 Å) C—S distances  /1.148 (3) Å in compound 2. These distances are less than the expected C=N double bond (1.28 Å) and are close to the C≡N triple bond distance  Å], as seen in Fig. 2Cg⋯Cg distances of 3.3065 (8) Å and 3.3218 (8), respectively, with a slippage for the latter of 1.154 Å].The coordination pattern of compound  2 Fig. 2. Thus, t2 ligand showed a ν(N—H) band at 3113 (m), and in compound 1, this band appeared at a lower energy, 3055 (m) cm−1. The ligand showed a diagnostic ν(C=S) band at 1179 cm−1, which shifted to ν(C=S), 1033(s) cm−1, owing to the change of neutral bzimtH2 ligand to the bzimtH− anionic form, coordinating through N,S donor atoms. The PPh3 ligand showed its characteristic ν(P—CPh) band at 1097(s) cm−1 in compound 1. A band at 1734 cm−1 was assigned to the coordinated cyano group. The IR spectroscopic bands of compound 2 are similarly assigned: ν(N—H), 3050 (m), ν(C=S), 1020 (m), ν(P—CPh), 1105 (s) and ν(C≡N), 1740(s) cm−1.The IR spectrum of the bzimtH2) has formed an N,S-bonded symmetrically bridged dinuclear compound, and so is the case with 1,3-imidazolidine-2-thione, and these are analogous to literature reports , 1,3-benzimidazoline-2-thione (bzimtH2), 1,3-imidazoline-2-thione (imtH2), and triethylamine were procured from Aldrich. The solvents  were of HPLC grade and were stored over molecular sieves. The precursor, PdCl2(PPh3)2, was prepared by a literature procedure  chloride, triphenylphosphine (PPh2(PPh3)2]Preparation of the precursor, [PdClin vacuo, m.p. 551-553 KPalladium(II) chloride  was dissolved in hot acetonitrile (25 mL) in a 50 mL round-bottom flask, and to it was added triphenylphosphine . The contents were refluxed for 1 h and the yellow complex formed was filtered and dried 1Preparation of 2(PPh3)2  in 10 mL of CH3CN, was added solid bzimtH2  followed by the addition of Et3N base (0.5 mL). The solution became yellowish orange and was refluxed for 6 h. The orange compound was formed on refluxing. It was separated and dissolved in a solution of methanol (4 mL) and dichloromethane (1 mL) in a culture tube. A slow evaporation of the reaction mixture over a period of one month, resulted in the formation of orange crystals of compound 1. Yield: 0.015 g; 65%; m.p. 511–513 K. Analysis found: C, 57.71; H, 3.84; N, 7.50; C52H40N6P2Pd2S2 (1087.8) requires: C, 57.40; H, 3.70; N, 7.72%. IR Data : ν(N—H), 3055 (m); ν(C–H), 2950 (m), 2920 (s), 2852 (m); ν(C≡N), 1734 (s), ν(C—C) + δ(N—H) + δ(C—H), 1635 (m), 1440 (s), 1380 (m); ν(P—CPh), 1097 (s); ν(C=S), 1033 (s). Ligand IR Data: ν(N—H), 3113 (m), ν(C—H), 3078 (m); 2981 (s); ν(C≡N) 1513 (s), δ(N—H), 1467 (s), 1381 (m); ν(C=S), 1179 (s). The compound is partially soluble in dichloromethane, but soluble in methanol and chloroform.To a solution of PdCl2Preparation of 2(PPh3)2  in 10 mL of CH3CN, was added solid imtH2  followed by the addition of Et3N base (0.5 mL). The solution became yellowish orange and was refluxed for 6 h. The orange compound was formed on refluxing and was separated. It was dissolved in a solution of methanol (4 mL) and dichloromethane (1 mL) in a culture tube. Slow evaporation of the reaction mixture over a period of one month formed yellowish-orange crystals of compound 2. Yield: 0.020 g; 69%; m.p. 485–488 K. Analysis found: C, 53.21; H, 3.92; N, 8.48; C44H36N6P2Pd2S2·0.58(CH3CN) (1011.5) requires: C, 53.58; H, 3.73; N, 8.36%. IR bands : ν(N—H), 3050 (m); ν(C—H), 3081 (s), 3005 (m), 2968 (m), 2938 (m); ν(C≡N), 1740 (s), d(N—H) + ν(C≡N) + δ(C—H), 1581 (s), 1479 (s), 1401(s); ν(C=S), 1020 (m); ν(P—CPh), 1105 (s); Ligand IR data: ν(N—H), 3130 (s), ν(C—H), 2983 (m); 2876 (s); ν(C≡N) 1586 (s), δ(N—H), 1478 (s), 1266 (m); ν(C=S), 1120 (m). The compound is soluble in methanol, chloroform and partially in dichloromethane.To the solution of PdCl6.Uiso(H) = 1.2Ueq(C). The structure of 2 contains partially occupied acetonitrile solvent molecules with occupancies of 0.33 and 0.25.Crystal data, data collection and structure refinement details are summarized in Table 510.1107/S2056989023000166/ex2063sup1.cifCrystal structure: contains datablock(s) 1, 2. DOI: 10.1107/S2056989023000166/ex20631sup2.hklStructure factors: contains datablock(s) 1. DOI: 10.1107/S2056989023000166/ex20632sup3.hklStructure factors: contains datablock(s) 2. DOI: 2234599, 2234598CCDC references:  crystallographic information; 3D view; checkCIF reportAdditional supporting information:


The title charge-neutral complex is a low-spin complex with a moderately distorted pseudo-octahedral coordination environment of the metal ion. As a result of their asymmetric shape, the molecules stack into chains, which eventually pack into layers and, finally, into a three-dimensional network connected by weak C—H⋯N, C—H⋯C hydrogen bonds and C—H⋯π interactions. II(C17H12BrN6O)2]·2MeOH, consists of a charge-neutral complex molecule and two independent molecules of methanol. In the complex molecule, the two tridentate ligand molecules 2--6-(1H-pyrazol-1-yl)pyridine coordinate to the FeII ion through the N atoms of the pyrazole, pyridine and triazole groups, forming a pseudo-octahedral coordination sphere around the central ion. In the crystal, neighbouring asymmetric molecules are linked through weak C—H(pz)⋯π(ph) interactions into chains, which are then linked into layers by weak C–H⋯N/C interactions. Finally, the layers stack into a three-dimensional network linked by weak interlayer C—H⋯π interactions between the methoxy groups and the phenyl rings. The intermolecular contacts were quantified using Hirshfeld surface analysis and two-dimensional fingerprint plots, revealing the relative contributions of the contacts to the crystal packing to be H⋯H 34.2%, H⋯C/C⋯H 25.2%, H⋯Br/Br⋯H 13.2%, H⋯N/N⋯H 12.2% and H⋯O/O⋯H 4.0%. The average Fe—N bond distance is 1.949 Å, indicating the low-spin state of the FeII ion. Energy framework analysis at the HF/3–21 G theory level was performed to quantify the interaction energies in the crystal structure.The unit cell of the title compound, [Fe The two independent methanol molecules form O—H⋯N hydrogen bonds with the triazole (trz) rings of the ligand molecules Fig. 1. The cends Fig. 1.6 coordination environment , where φi is the angle N–Fe–N′ , where θi is the angle generated by superposition of two opposite faces of an octahedron  but is, however, in the expected range for bisazolepyridines and similar ligands (see below). The calculated continuous shape measure (CShM) value relative to the ideal hO symmetry is 2.24  Å . Through weak intermolecular C—H⋯ N/C interactions in the range 3.128 (14)–3.734 (11) Å . The layers stack with interlayer interactions limited to C—H⋯N(trz) and C—H⋯π(ph) contacts involving the methyl groups . The voids between the layers are occupied by methanol molecules, which also participate in bonding between neighbouring layers ⋯π(ph) intermolecular contact between the pyrazole (pz) and phenyl (ph) groups respectively Table 1. The monÅ Table 1, neighbone Fig. 2b,c. Theps Fig. 2c. The v4.CrystalExplorer  to 2.4335 (blue) a.u. , the dispersion forces (Edis) and the total energy diagrams (Etot), are shown in Fig. 5Edis), reflecting the dominating interactions in the lattice of the neutral asymmetric molecules. The topology of the energy framework resembles the topology of the interactions within and between the layers described above. The calculated values Etot are in the range 65.2–87.6 kJ mol−1 for intrachain and intralayer interactions, whereas for the interlayer interactions they are within 7.7–23.4 kJ mol−1. The colour-coded interaction mappings within a radius of 3.8 Å of a central reference molecule for the title compound together with full details of the various contributions to the total energy (Etot) are given in the supporting information.The energy framework  change correspondingly, and in the low-spin state they are systematically lower than in the high-spin state. Table 2A search of the Cambridge Structural Database ](BF4)2 prepared by dissolving L = 2--6-(1H-pyrazol-1-yl)pyridine  and Fe(BF4)2·6H2O  in boiling acetone, to which chloroform (5 ml) was then added. The middle layer was a methanol–chloroform mixture , which was covered by a layer of methanol (10 ml), to which 100 µl of NEt3 was added dropwise. The tube was sealed, and black cubic single crystals appeared in 3–4 weeks (yield ca 60%). Elemental analysis calculated for C36H32Br2FeN12O4: C, 47.39; H, 3.54; N, 18.42. Found: C, 47.11; H, 3.74; N, 18.40.The synthesis of the title compound is identical to that reported recently for a similar complex (Seredyuk 8.Uiso(H) = 1.2–1.5Ueq(C)]. O-bound H atoms were refined with Uiso(H) = 1.5Ueq(O).Crystal data, data collection and structure refinement details are summarized in Table 310.1107/S2056989022010179/dj2053sup1.cifCrystal structure: contains datablock(s) I. DOI: 10.1107/S2056989022010179/dj2053Isup2.hklStructure factors: contains datablock(s) I. DOI: Click here for additional data file.10.1107/S2056989022010179/dj2053Isup4.cdxSupporting information file. DOI: 10.1107/S2056989022010179/dj2053sup3.pdfIncludes energy framework data and schematic structures of similar neutral Fe(II) complexes. DOI: 2215273CCDC reference:  crystallographic information; 3D view; checkCIF reportAdditional supporting information: