Vol 68, No 9 (2023)

Bis-chelate nickel complex of composition [L2Ni(H2O)2](BF4)2 (4), where L = 1,3-dibenzhydryl-5-(pyridin-2-yl)-5-oxo-1,3,5-diazaphosphorinane, and tris-chelate complexes 5 and 6 of composition [L3Ni](BF4)2, where L = 2-diethylphosphorylpyridine and 2-diisopropylphosphorylpyridine, based on 1,4-N,O ligands L2–L4 with phosphoryl groups of acyclic and cyclic structure have been prepared. The structure and composition of complexes 4–6 were confirmed by mass-spectrometry, IR spectroscopy, thermogravimetric and elemental analysis. The structure of complexes 4-EtOH and 5 in crystals has been established by X-ray diffraction study. Cytotoxic properties toward M-HeLa and HuTu80 cancer cells and Chang Liver normal cell lines for the previously prepared nickel(II) complexes 1–3 based on 2-(oxophospholane)pyridines and the nickel(II) complexes obtained in this work have been studied. It has been found that the complexes with ligands containing cyclic phosphoryl groups show higher cytotoxicity toward cancer cells as compared with the complexes with their acyclic analogs.

Copper(II) catecholate complexes based on 3,6-di-tert-butyl-o-benzoquinone with N-donor ligands of the phenanthroline series have been synthesized: (3,6-Cat)Cu(Phen) (I), (3,6-Cat)Cu(DPQ) (II), and (3,6-Cat)Cu(DPPZ) (III), where 3,6-Cat is the 3,6-di-tert-butyl-o-benzoquinone dianion, Phen is phenanthroline, DPQ is dipyrido[3,2-d:2',3'-f]quinoxaline, and DPPZ is dipyrido[3,2-a:2',3'-c]phenazine. The synthesized copper(II) complexes demonstrate intramolecular ligand-to-ligand charge transfer responsible for their intense violet color. The electronic structure of the synthesized chromophores was studied by electronic spectroscopy, cyclic voltammetry, and quantum-chemical calculations. The molecular and crystal structures of the synthesized compounds were determined by X-ray diffraction analysis (CIF files CCDC 2 250 975 (I⋅THF), 2 250 976 ([(II⋅THF)(II)]⋅3THF), 2250977 (II)).

Zinc(II) complexes 2, 3, and 5 with redox-amphoteric o-indophenol ligands were prepared. The molecular structures of tetracoordinate complex 2 and hexacoordinate complex 3 were determined by single-crystal X-ray diffraction. The antioxidant properties of indophenols and their complexes were studied by cyclic voltammetry (CVA) and EPR spectroscopy. Complexation of indophenols increases the oxidation potentials by more than 0.84 V and leads to the formation of stable metal-containing radicals.

A series of bis-cyclometallated iridium(III) complexes with various 2-aryl-1-benzylbenzimidazoles (aryl is 4-chlorophenyl, 4-tert-butylphenyl, 3,4-dimethoxyphenyl) and 4,4'-dicarboxy-2,2'-bipyridine have been prepared. The synthesized complexes have been studied by 1H NMR spectroscopy, high-resolution mass spectrometry, X-ray diffraction analysis, spectrophotometry, luminescent spectroscopy, and cyclic voltammetry. In the electronic spectra of the complexes, the absorption bands show a noticeable bathochromic shift with an increase in the electron-donating properties of the benzimidazole ligand. In solution, the complexes exhibit photoluminescence in the yellow–red region of the spectrum with a quantum yield in the range of 0.4–7.7% and an excited state lifetime in the range of 71–408 ns. According to cyclic voltammetry data, quasi-reversible redox transitions are observed in solutions of the studied complexes (Eox = 1.16–1.57 V vs. SHE, acetonitrile).

Scandium(III) benzoyltrifluoroacetonate [Sc(btfac)3] was synthesized, purified, and characterized by elemental analysis and 1H NMR spectroscopy. Its structure was determined by single-crystal X-ray diffraction at 150 K. The complex has a molecular structure and is an axial isomer. All ligands in it are bidentate-cyclic coordinated; scandium is in a distorted octahedral environment, d(Sc–O) = 2.0681(2)–2.094(2) Å. There are two types of stacking interactions. The thermal properties in the condensed phase were studied by thermal analysis and differential scanning calorimetry (DSC). The temperature, enthalpy, and entropy of melting of the complex were determined as 399.1 ± 0.5 K, 
 = 36.8 ± 1.3 kJ/mol, and 
 = 92.2 ± 3.3 J/(K mol), respectively. The temperature-dependent saturated vapor pressure of [Sc(btfac)3] was determined in the temperature range 413–443 K by the flow (transpiration) method. The thermodynamic characteristics of vaporization at an average temperature were calculated: 
 = 135 ± 4 kJ/mol, and 
 = 212 ± 9 J/(K mol). The structure and thermal properties of scandium benzoyltrifluoroacetonate were compared to those of similar scandium tris-β-diketonate complexes

Coordination compounds [Co(DMF)6][B20H18] containing isomeric forms of the macropolyhedral cluster [trans-B20H18]2– and [iso-B20H18]2– have been synthesized. Complex [Co(DMF)6][trans-B20H18] has been prepared by the reaction of a salt of the boron cluster anion with cobalt(II) chloride in dimethylformamide; complex [Co(DMF)6][iso-B20H18] has been isolated when recrystallized from water during spontaneous isomerization of the macropolyhedral cluster. The coordination compounds have been identified by IR spectroscopy, 11B NMR spectroscopy, and X-ray diffraction analysis.

The heteroleptic anionic complex (IPrPhH)[Co2(μ-Piv)2(μ-OSiMe3)(Piv)2] (I) was synthesized through the reaction of cobalt pivalate [Co(Piv)2]n with 1,3-bis(2,6-diisopropylphenyl)-2-phenylimidazolium iodide ([IPrPhH]I) and KN(SiMe3)2 and studied by X-ray diffraction both in the solvate-free form and in the form of solvate with pentane (I⋅0.75C5H12) (CCDC 2257678–2257679). Modeling of the probable mechanism of formation of complex I and evaluation of exchange coupling between paramagnetic centers in it were carried out by density functional theory method.

Reaction of bis(2-(diphenylphosphino)ethyl)benzylamine (PNP) and bis(2-methylpyridyl)benzylamine (NNN) with known closo-ruthenacarborane [3-H-3-Cl-3,3-(PPh3)2-3,1,2-RuC2B9H11] (1) leads to the formation of new ruthenium carborane complexes 3,3,3-(bis(2-(diphenylphosphino)ethyl)benzylamine)-closo-3,1,2-RuC2B9H11 (2) and 3,3,3-(bis(2-methylpyridyl)benzylamine)-pseudocloso-3,1,2-RuC2B9H11 (3), respectively. The resulting complexes have been studied by NMR and IR spectroscopy and time-of-flight MALDI MS. Geometry optimization of complex 2 obtained for the first time by quantum-chemical modeling reduces to the closo-configuration, while complex 3 is stable both in closo and pseudocloso forms. Using single-crystal X-ray diffraction, it has been found that complex 2 has a closo structure, whereas 3 has a pseudocloso structure. A study of the electrochemical properties showed that complexes 2 and 3 are capable of reversible oxidation.

A mixed-ligand complexation approach implying the reaction of metal carboxylates with the chelating tridendate diethylenetriamine (DETA) ligand has been applied to modify the structure of the layered coordination polymer based on lanthanum propionate (Prop). Lanthanum propionate monohydrate has been synthesized and characterized by a set of analytical methods to determine its crystal structure and chemical composition. The crystal structures of lanthanum propionate and nickel propionate complexes with DETA have additionally been determined. The native lanthanum propionate monohydrate [La2(H2O)2Prop6] has been proven to have a 2D-layered topology, whereas the mixed-ligand complex [La2(DETA)Prop6] ⋅ MeCN (where MeCN stands for acetonitrile) has a chain structure. A chemical solution deposition procedure has been developed to produce phase-pure oriented LaNiO3 thin films. These films exhibit metallic conductivity and can be used as conductive sublayers.

Trinuclear complexes Me4N[Ni3(µ3-F)(TFA)6(MeOH)2(H2O)] (1) and Me4N[M3(μ3-F)(TFA)6(py)3] (M = Mn (2), Co (3), Ni (4), Cu (5), Zn (6)) have been synthesized by crystallization from methanol solutions. Single-crystal X-ray diffraction shows that compounds 1–6 are composed of tetramethylammonium cations Me4N+ and trinuclear triangular anions [Ni3(µ3-F)(TFA)6(MeOH)2(H2O)]– (1) or [M3(μ3-F)(TFA)6(py)3]– (2–6) centered by the μ3-F atom. The bridging trifluoroacetate anions (TFA–) located along the triangle edges link pairs of M2+ cations, and the axial positions are occupied by MeOH, H2O, or pyridine (py) molecules. In 2, the pyridine molecules are nearly coplanar with the [M3F] triangle, while in the other structures they are turned almost perpendicularly. The different orientations of py molecules lead to different packing motifs: columns of alternating trinuclear anions and Me4N+ cations are formed in 2, while in 3–6 anions and cations form neutral layers. A significant role in the organization of structures 1–6 is played by non-covalent interactions, such as hydrogen bonds and stacking and CH···π interactions. Heating complexes 2–4 above 200°С turns out to lead to a stepwise thermal decomposition, which begins with the elimination of py and ends with the formation of d-metal fluoride above 300°С.