Volume 43, Nº 2 (2017)

Silver(I) nitrate complexes [AgNO₃(L)₂], where L is quinoline or 2-, 4-, and 8-methylquinoline, are synthesized and studied by the multinuclear NMR (¹H, ¹³C, ¹⁵N) method in acetonitrile. The influence of steric and electronic factors of the organic ligand on the NMR spectral parameters is revealed. The fast chemical exchange of the free and coordinated ligands is observed at room temperature. The ¹⁵N NMR spectra are most informative. The formation of a complex with 8-methylquinoline is impeded because of steric hindrances.

The coordination polymer of cobalt(II) nitrate with bicyclic bis(urea), 4,4,10,10-tetramethyl-1,3,7,9-tetraazaspiro[5.5]undecane-2,8-dione (Sk) {[Co(C₁₁H₂₀N₄O₂)₂(H₂O), Co(C₁₁H₂₀N₄O₂)₂(H₂O)₂]⁴⁺(NO₃^-)₄}_n (I), is synthesized for the first time, and its atomic structure is determined (CIF file CCDC no. 925792). The crystals of compound I are monoclinic: space group P2/c, a = 26.1284(6), b = 7.1763(2), c = 17.1825(5) Å, β = 105.042(3)°, V = 3111.43(15) ų, ρ_calcd = 1.474 g/cm³, Z = 2. The powder X-ray pattern at 293 K is refined using the Rietveld method to confirm the single-phase character of the obtained sample of powdered compound I: a = 26.1456(9), b = 7.1810(4), c = 17.1997(11) Å, β = 105.016(3)°, V = 3119.0(3) ų. The content of the major phase of compound I in the sample is 100 ± 1%, and impurity phases are absent. The crystal of compound I contains two types of chains oriented along the crystallographic direction [001] with similar structures but differed in the coordination numbers of the cobalt atoms. The Co(1) atom has a coordination number of 5 (trigonal bipyramid), and the coordination number of the Co(2) atom is 6 (octahedron). The nitrate anions are uncoordinated.

The complexes [Ph₃PR]₂[OsBr₆], R = cyclo-C₃H₅ (I), n-C₄H₉ (II), cyclo-C₆H₁₁ (III), CH₂C(O)Ph (IV), [Ph₃PPr]₂[OsBr₆] ∙ DMSO (V), and [Ph₃P(CH₂)₃PPh₃][OsBr₆] ∙ DMSO (VI) (CIF files CCDC nos. 1000171, 1000148, 1000172, 1000173, 1000147, and 1000149 for structures I–VI, respectively) were prepared by reactions of sodium hexabromoosmate with phosphonium bromides in dimethyl sulfoxide. According to X-ray diffraction data, phosphorus atoms in the cations have slightly distorted tetrahedral coordination (CPC angles, 105.2(3)°–115.5(3)°; P–C, 1.773(6)–1.814(6) Å). In the octahedral [OsBr₆]^2– anions, the Os–Br bond lengths are 2.4734(8)–2.5203(5) Å and the cis-BrOsBr and trans-BrOsBr angles are 88.38(2)°–91.53(3)° and 177.276(18)°–180°, respectively. The structural organization in the crystals is formed by H∙∙∙Br (2.74–3.04 Å) and H∙∙∙O_DMSO (2.28–2.63 Å) ion–ion hydrogen bonds.

Comprehensive comparison between the reaction of N,N'-cyclohexane-1,2-diylidene-bis(4-methoxybenzoylhydrazide) (CHMBH) with HgCl₂ and Cu(NO₃)₂ · 2.5H₂O salts have been investigated, including the synthesis, structure and kinetic of complex formation. The reactions of CHMBH with HgCl₂ or Cu(NO₃)₂ · 2.5H₂O at the same synthetic conditions have been shown to produce completely different type of complexes: [Hg(CHMBH)Cl₂] · CH₃CN (I) and [Cu₃(μ₃-OH)(CTMB)₃(NO₃)₂(CH₃CN)₂] · 5CH₃CN · H₂O (II) (CTMB = cyclohexotriazole-3-(4-methoxybenzamide)). The prepared compounds were characterized using different techniques (NMR, IR, UV-Vis and mass spectroscopies, microelemental analysis, thermogravimetry as well as X-ray powder differection and X-ray single crystal crystallography for I (CIF file CCDC no. 1503398). X-ray crystallography shows that the isolated product of I is a mononuclear complex which contains the [Hg(CHMBH)]²⁺ core. While, the isolated product of II was a trinuclear Cu(II) cluster [Cu₃(μ₃-OH)(CTMB)₃(NO₃)₂(CH₃CN)₂] · 5CH₃CN · H₂O which contains three differently coordinated copper sites. Kinetic studies on the formation of I have been also investigated and compared with that of II. In case of I, the reaction was so slow and exhibits a first-order dependence on the concentration of metal salt and a first-order dependence on the concentration of CHMBH. While in II, the study shows that the reaction is fast and occurs in three distinct phases.

A new Co(II)-based complex { [Co₂(L)(4,4'-Bipy)₂] · CH₃CN} _n (I) (H4L = 5,5'-(biphenyl-4,4'- diyl-bis(methylene))bis(oxy)diisophthalic acid, 4,4'-Bipy = 4,4'-bipyridine) has been synthesized and structurally characterized. Single-crystal X-ray analysis (CIF file CCDC no. 1406388) reveals that compound I has 3D pcu topology. The incorporation of the drug 5-fluorouracil (5-FU) into the desolvated I was around 15.0 wt % of dehydrated I. Complex I also shows a pH-triggered controlled drug release property. In addition, we used semiempirical AM1 method to investigate the adsorption of 5-FU to I at the molecular level.