A new complex of copper(II) with methyl-5-(trifluoromethyl)pyrazol-3-yl-ketazine (H2L) was synthesized with the composition [Cu2L2]∙C2H5OH (1). Recrystallization of the sample from DMSO yielded a single crystal of the composition [Cu2L2((CH3)2SO)] (2). The coordination compounds were studied by single-crystal X-ray diffraction analysis, IR spectroscopy, and static magnetic susceptibility method. The data obtained indicate that the polydentate ligand is coordinated by both acyclic nitrogen and heterocyclic nitrogen atoms. The cytotoxic activity of the ligand and complex 1 was investigated on human cell lines MCF7 (breast adenocarcinoma), Hep2 (laryngeal carcinoma), A549 (lung carcinoma), HepG2 (hepatocellular carcinoma), and MRC5 (non-tumor lung fibroblasts). The complex was shown to have a pronounced dose-dependent cytotoxicity towards these cell lines with LC50 values in the range of 0.18–4.03 μM.

New coordination compounds of copper(I), copper(II), cobalt(II), and nickel(II) with 2,4-dimethylpyrazolo[1,5-а]benzimidazole (L) were synthesized and studied. The complexes [CuLCl] (I), [CuLBr] (II), [CuL2Cl2] (III), [CuL2(NO3)2]·H2O (IV), [CoL2Cl2]·0.5H2O (V), [CoL2(NO3)2]·0.5H2O (VI), and [NiL2(NO3)2]·0.5H2O (VII) were studied by IR spectroscopy and powder and single crystal X-ray diffraction (CCDC nos. 2321779 ([CuL2Cl2]), 2321780 ([CoL2(NO3)2])). The results indicate that the coordination polyhedron in 2,4-dimethylpyrazolo[1,5-а]benzimidazole complexes is formed by the nitrogen atoms of the monodentate ligand and the coordinated anion. The cytotoxic and cytostatic properties of L and complexes I–III were studied in relation to the HepG2 hepatocellular carcinoma cells.

Abstract—Dimethyl sulfoxide (DMSO) solutions of [FeL2](ReO4)2⋅1.5H2O (1), the iron(II) perrhenate complex with 2,6-bis(benzimidazol-2-yl)pyridine (L), are characterized by physicochemical methods, namely, by static magnetic susceptibility measurements, conductometry, and UV–Vis spectrophotometry. As found previously, complex 1 exhibits a sharp high-temperature spin crossover (SCO): 1А1 ↔ 5Т2. The temperature-dependent μeff(Т) study of complex 1 in DMSO showed that the SCO also manifests itself in solution. The 298 K electrical conductivity of DMSO solutions implies that complex 1 is almost completely dissociated in the range of concentrations studied from 3.6 × 10–6 to 9.12 × 10–4 mol/L. An absorption peak is found in the UV region of the spectrum, which is almost independent of temperature. In the visible region, two combined absorption peaks are observed at 520–560 nm, responsible for FeL2+ and FeL_2^2 + complex formation and varying with temperature and L concentration.

A quantum chemical study was carried out for a number of iron(II) complexes [FeL 2 ]A i · n H 2 O (L = 2,6‐bis(1 H ‐imidazole‐2‐yl)pyridine (L 1 ); 2,6‐(4,5‐dimethyl‐1 H ‐imidazole‐2‐yl)pyridine (L 2 ); 2,6‐bis(1 H ‐benzimidazole‐2‐yl)pyridine (L 3 ); A = ReO 4 − , B 10 H 10 2− , B 12 H 12 2− ; n = 0–2). These complexes exist in the low spin (LS) form 1 A 1 (total electron spin S = 0) at room temperature and switch to the high spin (HS) form 5 T 2 (S = 2) upon heating. The experimental isomeric shift and quadrupole splitting values for compounds with L 2 exceed those for compounds with L 1 and L 3 by <0.02> mm/s and <0.1> mm/s, respectively (for LS forms). Such a discrepancy between MS parameters can be explained by the assumption that chemical bonding between the iron ion and the surrounding nitrogen atoms in the compounds with L 2 may be more ionic in character than that in the compounds with L 1 and L 3 . At the same time, the results obtained with the TPSSh hybrid meta‐GGA functional gave a better agreement with the experimental data than those obtained with the B3LYP exchange‐correlation functional.

Structures of two new copper(II) chloride complexes with 2,5-bis(ethylthio)-1,3,4-thiadiazole (L), mononuclear CuL2Cl2 and tetranuclear Cu4L4Cl8, are determined by X-RAY diffractometry. The polycrystalline phase of the CuL2Cl2 complex is determined and studied by CHN analysis, IR spectroscopy, powder XRD, and static magnetic susceptibility methods.

New iron(II) complexes with 2,6-bis(1H-imidazol-2-yl)-4-methoxypyridine (L) of the composition [FeL2]An∙mH2O (A = SO42−, n = 1, m = 2 (I); A = ReO4−, n = 2, m = 1 (II); A = Br−, n = 2, m = 2 (III)) have been synthesized and investigated. To determine the coordination ability of the ligand, a single crystal of a copper(II) complex of the composition [CuLCl2] (IV) was obtained and studied by X-ray technique. Compounds I–III were studied using methods of X-ray phase analysis, electron (diffuse reflection spectra), infrared and Mössbauer spectroscopy, static magnetic susceptibility. The study of the µeff(T) dependence showed that the 1A1 ↔ 5T2 spin crossover manifests itself in the compounds. The spin crossover is accompanied by thermochromism: there is a distinct color change orange ↔ red-violet.

The results of synthesis and study of magnetically-active iron(II) complexes with polynitrogen heterocyclic ligands and outer-sphere boron cluster anions have been considered. Derivatives of 1,2,4-triazole, tris (pyrazol-1-yl)methane, and 2,6-bis(imidazol-2-yl)pyridine have been used as ligands, decahydro- closo -decaborate, dodecahydro- closo- dodecaborate, decachloro- closo -decaborate, and 1,5,6,10-tetra(R)-7,8-dicarba- nido -undecaborates (R = H, Cl, Br) have been studied as outer-sphere anions. A number of iron(II) complexes showing spin crossover accompanied by thermochromism in the majority of cases has been obtained. Effect of ligand nature and cluster anion on temperature ( T c ) and spin transition character has been considered. In particular, it has been shown that introduction of substituent increasing electron density over the system of conjugated three-centered two-electron bonds in cluster anion leads to increase in the field strength of ligand bound to anion via network of hydrogen bonds.

Reaction of pyridine-2,6-dicarbaldehyde with hexane-3,4-dione and ammonium acetate affords 2,6-bis(4,5-diethyl-1 H -imidazol-2-yl)pyridine (L) which was used as ligand in the synthesis of iron( ii ) chloride complex [FeL 2 ]Cl 2 •H 2 O. Conclusions about the structure of the coordination site of the complex were drawn based on the results of IR spectroscopy, EXAFS spectroscopy, static magnetic susceptibility studies, and quantum chemical calculations.

A procedure for the synthesis of the new ditopic ligand combining in the structure 1- and 5-substituted tetrazolyl cycles, 5-(2-(1 H -tetrazol-1-yl)phenyl)-1 H -tetrazole (HL), is developed. The coordination compounds of Co(II) and Cu(II) halides [Co(HL) 2 Cl 2 ], [Cu(HL) 2 Cl 2 ], [Cu(HL) 2 Br 2 ], and [CuL 2 (H 2 O)] n based on ligand HL are synthesized. The complexes are studied by elemental analysis, diffuse reflectance spectroscopy, IR spectroscopy, X-ray diffraction (XRD), and static magnetic susceptibility. The crystal structure of the molecular coordination polymer [CuL 2 (H 2 O)] n is determined by XRD (CIF file CCDC no. 2127210). The temperature and field dependences of the magnetization show that the magnetic properties of the synthesized Cu(II) complexes are due to exchange interactions in one-dimensional chains of the copper ions ( S = 1/2). For complex [Cu(HL) 2 Br 2 ], the parameters are shifted toward the enhancement of the antiferromagnetic interaction compared to the analog containing the chloride ion.

New coordination compounds of copper(II) with 2,5-bis(ethylthio)-1,3,4-thiadiazole (L1) and 2,5-bis(pyridylmethylthio)-1,3,4-thiadiazole (L2) with compositions Cu(L1)2Br2, Cu(L1)(C2N3)2, Cu(L2)Cl2, and Cu(L2)Br2 were prepared. The complexes were identified and studied by CHN analysis, infrared (IR) spectroscopy, powder X-Ray diffraction (XRD), and static magnetic susceptibility. The crystal structures of Cu(II) complexes with L1 were determined. The structures of the coordination core of complexes Cu(L2)Cl2 and Cu(L2)Br2 were determined by Extended X-ray absorption fine structure (EXAFS) spectroscopy. Magnetization measurements have revealed various magnetic states in the studied complexes, ranging from an almost ideal paramagnet in Cu(L1)2Br2 to alternating-exchange antiferromagnetic chains in Cu(L1)(C2N3)2, where double dicyanamide bridges provide an unusually strong exchange interaction (J1/kB ≈ −23.5 K; J2/kB ≈ −20.2 K) between Cu(II) ions. The cytotoxic activity of copper(II) complexes with L2 was estimated on the human cell lines of breast adenocarcinoma (MCF-7) and hepatocellular carcinoma (HepG2).

Методом РСА установлена структура двух новых комплексов хлорида меди(II) c 2,5-бис(этилтио)-1,3,4-тиадиазолом (L) CuL2Cl2 и Cu4L4Cl8, которые имеют моноядерное и тетраядерное строение соответственно. Поликристаллическая фаза комплекса CuL2Cl2 идентифицирована и исследована методами CHN-анализа, ИК-спектроскопии, РФА, статической магнитной восприимчивости.

Синтезированы и исследованы новые координационные соединения железа(II) c трис(пиразол-1-ил)метаном (HC(pz)3), содержащие дицианоаргентат- и дицианоаурат-ионы состава [Fe(HC(pz)3)[Ag(CN)2]2]·2H2O (1·2H2O), [Fe(HC(pz)3)[Au(CN)2]2]·H2O (2·H2O). Соединения изучены с помощью методов рентгенофазового анализа, электронной (спектроскопии диффузного отражения), инфракрасной и мессбауэровской спектроскопии, статической магнитной восприимчивости. Полученные данные позволяют сделать вывод, что координационный полиэдр в исследуемых комплексах формируется за счет трех атомов азота тридентатно-циклически координированного лиганда HC(pz)3, двух атомов азота бидентатно-мостикового аниона [М(CN)2]– и атома азота (либо углерода) монодентатно координированного аниона. В обоих соединениях образуются координационные узлы, выступающие предпосылкой для проявления в них спин-кроссовера, FeN6 и FeСN5. Рассчитаны значения параметров расщепления в кристаллическом поле для низко- и высокоспиновой форм комплексов 1·2H2O и 2·H2O. Изучены зависимости μэфф(Т) в диапазоне 80—400 K для комплексов 1 и 2, полученных при дегидратации 1·2H2O и 2·H2O. Обнаружено, что в обоих комплексах проявляется спин-кроссовер (СКО) 1А1 ↔ 5Т2, в 1 наблюдается одноступенчатый переход, в 2 тип перехода изменяется на двухступенчатый.

New coordination compounds of iron(II) with tris(pyrazol-1-yl)methane (HC(pz)3) containing dicyanoargentate and dicyanoaurate ions of the composition [Fe(HC(pz)3)[Ag(CN)2]2]·2H2O (1·2H2O), [Fe(HC(pz)3)[Au(CN)2]2]·H2O (2·H2O) are synthesized and studied. The compounds are analyzed by powder X-ray diffraction, electron (diffuse reflectance spectroscopy), infrared, Mössbauer spectroscopy, and static magnetic susceptibility. The data obtained enable the conclusion that in the complexes under study, the coordination polyhedron is formed by three nitrogen atoms of the tridentately-cyclically coordinated HC(pz)3 ligand, two nitrogen atoms of the bidentate bridging [М(CN)2]– anion, and the nitrogen (or carbon) atom of the monodentately coordinated anion. Coordination cores acting as premises for spin crossover (SCO) in them (FeN6 and FeСN5) are formed in both compounds. Crystal field splitting parameters are calculated for low- and high-spin forms of 1·2H2O and 2·H2O complexes. Dependences μeff(Т) are studied in the range of 80-400 K for 1 and 2 complexes obtained by dehydration of 1·2H2O and 2·H2O. 1А1 ↔ 5Т2 SCO is found to occur in both complexes; in 1, a one-step transition is observed; in 2, the transition becomes two-step.

Министерство науки и высшего образования Российской Федерации Российская академия наук Научный совет по неорганической химии РАН Научный совет по аналитической химии РАН Научный совет по химической технологии РАН Российское химическое общество имени Д.И

Iron(II) coordination compounds containing a new ligand, 2,6-bis(4,5-dimethyl-1H-imidazol-2-yl)pyridine (L), of composition [FeL2](NO3)(2)center dot H2O (1 center dot H2O), [FeL2](ClO4)(2)center dot 0.5H(2)O (2 center dot 0. 5H(2)O), [FeL2]SO4 center dot 0.5H(2)O (3.0.5H(2)O), or [FeL2](ReO4)(2)center dot 2H(2)O (4 center dot 2H(2)O) have been synthesized and studied by UV-vis (diffuse reflectance), infrared, extended X-ray absorption fine structure (EXAFS), and Mossbauer spectroscopies, as well as X-ray diffraction and static magnetic susceptibility methods. The structure of a copper(II) complex with L of composition [CuL2] SO4 center dot 3H(2)O has been successfully determined. The analysis of the mu(eff)(T) dependence in the temperature range of 80-520 K showed that complexes [FeL2](NO3)(2)center dot H2O, [FeL2](ClO4)(2)center dot 0.5H(2)O, and [FeL2](ReO4)(2)center dot 2H(2)O and their dehydrated counterparts are subject to high-temperature spin crossover (1)A(1) <-> T-5(2).

New iron(II) coordination compounds with 2,6-bis(4,5-dimethyl-1H-imidazol-2-yl)pyridine (L) and closo-borate(2–) anions [FeL2]B10H10⋅2H2O and [FeL2]B12H12⋅H2O have been synthesized. The compounds have been identified and studied by CHN analysis, electron spectroscopy (diffuse reflection spectroscopy), IR, Mössbauer, and EXAFS spectroscopies, X-ray powder diffraction, and static magnetic susceptibility. The structures of the coordination knots of complexes [FeL2]B10H10⋅2H2O and [FeL2]B12H12⋅H2O has been obtained by modeling the EXAFS spectra. The ligand is coordinated by the iron(II) ion in a tridentate-cyclic manner by two nitrogen atoms of imidazole cycles and a nitrogen atom of pyridine to form the FeN6 coordination knot. The study of the temperature dependence of the magnetic susceptibility in the range of 80–500 K has showed that the high-temperature spin-crossover 1А1 ↔ 5Т2 manifests itself in the obtained compounds.

New coordination compounds of cobalt(II), nickel(II), and copper(II) halides with 2-(3,5-dimethylpyrazol-1-yl)benzimidazole (L) of the composition [CoLCl2] (1), CoL2Cl2 · 2H2O · EtOH (2), [NiL(H2O)4]Cl2 · H2O · EtOH (3), NiL2Cl2 · 2H2O · EtOH (4), and [CuL2Br]Br · H2O (5) were synthesized. The compounds were characterized by electronic (diffuse reflectance) spectroscopy, IR spectroscopy, and powder X-ray diffraction. The crystal structures of compounds 1, 3, and 5 were determined by single-crystal X-ray diffraction. The cytotoxic properties of the ligand and compound 5 were evaluated in the Hep-2 cell line.