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Ruthenium complexes of some tridentate and bidentate benzimidazole-, benzothiazole- and pyridine-derived ligands have been prepared as their PF f6 p− salts, and their constitutions have been confirmed by elemental analysis, 1H-n.m.r. spectroscopy and electrochemistry. The complexes are redox-active, displaying a metal-centred RuII/ RuIII oxidation process and sequential ligand-localized reduction processes. Both the 2-(2′-pyridyl)benzimidazole complex [Ru(PybimH)3]2+ and the 2,2′-dipyridylamine one, [Ru(DpyaH)3]2+ behave as weak Brønsted-Lowry acids. The secondary amino nitrogen of each DpyaH in the [Ru(DpyaH)3]2+ complex can be deprotonated with hydride anion, and then acts as a strong nucleophile, allowing selective N-alkylation by alkyl halides. Most of the complexes exhibit ligand-localized luminescence emission at ambient temperature. The strong intrinsic fluorescences of 2-(2′-quinolyl)-N-methylbenzimidazole and 2-(2′-pyridyl)-benzimidazole are quenched when they are coordinated to RuII, and emission from the chelates entailing 5-nitro-1:10-phenanthroline occurs only from the non-nitrated ligands.

A new chainlike polymer, Na[Ce(dipic)(H2O)3]2 [CrMo6H6O24] · 13H2O (H2dipic = pyridine-2,6-dicarboxylic acid) (1), has been synthesized and characterized by elemental analysis; IR and XPS spectroscopy, TG analysis, and single-crystal X-ray diffraction. Compound (1) is built up of Anderon-type polyoxoanions as structural motifs and cerium–dipic coordination fragments as linkers to yield an unprecedented one-dimensional chain. Such chains are further in close contact forming a three-dimensional supramolecular framework with channels via extensive hydrogen-bonding interactions among polyoxoanions, dipic ligands and water molecules. Furthermore, the magnetic properties of compound (1) have been studied by measuring their magnetic susceptibility in the temperature range 2–300 K.

Complexes of cobalt(II) and copper(II) with 5-amino-3,4-dimethylisoxazole (5-ADI) have been prepared and studied by means of magnetic susceptibility measurements, near and far i.r. spectra, electronic spectroscopy and, when possible, conductivity measurements. The 5-ADI generally behaves as bridging (Nring-, O- or Nring-, -NH2) ligand. All the complexes have an octahedral sterochemistry, except Co(5-ADI)2X2 (X = Cl, Br), Co2(5-ADI)7I4 which are tetrahedral and Cu(5-ADI)2 (ClO4)2 · 4 H2O which is square planar.

Six metal(II) complexes with quercetin ML2 · nH2O [L = quercetin (3-OH group deprotonated); M = Mn, Co, Ni, Cu, Zn, and Pb; n = 2 or 3] have been prepared and characterized by elemental analysis, complexometric titration, thermal analysis, conductivity, i.r., u.v., 1H-n.m.r. and fluorescence spectral techniques as well as by cyclic voltammetry. The antioxidative and anti-tumour activities of quercetin · 2H2O and the complexes were tested by both the MTT and SRB methods. The results show that the suppression ratios of the complexes against the tested tumour cells are superior to quercetin · 2H2O. The effect of ZnL2 · 3H2O reacting with calf thymus DNA was studied by fluorescence methods. The Zn-complex binding to DNA has been determined by fluorescence titration in 0.05 M Tris-HCl, 0.5 M NaCl buffer (pHb = 7.0). The results indicate that the interaction of the complex with DNA is very evident.

The complexes CuII(4-Mepy)2Ag2(CN)4 (1) and CuII(4-Mepy)3Ag2−x CuI x (CN)4 (2) (4-Mepy = 4-methylpyridine, x = 0.07) were isolated from a reaction mixture containing 4-Mepy, K[Ag(CN)2] and CuSO4. I.r. spectra indicated the presence of both monodentate and bridging cyano groups in (1) and (2), confirmed by their known structures, both consisting of neutral zigzag chains. Two neighbouring chains in (2) are linked by argentophilic interactions between Ag atoms of bridging dicyanoargentate anions, whose positions are partly occupied by CuI ions to the extent of 7 at.%, with an unusually short Ag...Ag distance of 2.9264(5) Å, to form a ladder. Individual ladders are tied together as sheets by weaker argentophilic interactions between silver atoms of interdigitated monodentate dicyanoargentate anions of two different ladders. Thermal decomposition of (2) occurs in two separated stages. In the first stage, three 4-Mepy molecules are liberated from the formula unit and, in the second stage, redox decomposition of the cyano groups occurs. The thermal decomposition of (1) is more complicated as the release of two 4-Mepy molecules is overlapped by decomposition of one cyano group followed by further redox decomposition of the remaining cyano groups.

New vic-dioxime ligands and their CuII, CoIII, NiII and VOIV complexes have been prepared and characterized by elemental analyses, i.r. and u.v. spectra, magnetic moments and molar conductance data. The CoIII complexes are diamagnetic. The 1H- and 13C-n.m.r. and g.c./m.s. spectra of the vic-dioxime ligands and their CoIII complexes were recorded. The compounds are all non-electrolytes.

Tunable organometallic Lewis acid catalysts were developed by combining salicylic acid (H2-Sal) with benzoic acid (H-Ben), 4-fluorobenzoic acid (H-BenF) and 3-thiophenic acid (H-Th), as coligands for mixed bis-carboxylate titanocene complexes. Three air-stable complexes [Cp2Ti(η1-HSal)(η1-Ben)] (1), [Cp2Ti(η1-HSal)(η1-BenF)] (2) and [Cp2Ti[η1-HSal][(η1-Th)] (3) were prepared in high yields by the reaction of salicylato titanocene chelate with carboxylate ligands. The mixed bis-carboxylate titanocene complexes were fully characterized by physicochemical and spectroscopic methods. Single-crystal X-ray diffraction studies revealed Ti–O(H-Sal) bond distances in 1, 2 and 3 of 1.972(3), 1.9245(18) and 1.912(5) Å, respectively, while the bond distances involving the coligands of 1, 2 and 3 are 1.908(3) Å (Ti–OBen), 1.9296(19) Å (Ti–OBenF) and 1.945(5) Å (Ti–OTh), respectively. These bis-carboxylate titanocene complexes showed satisfactory activities and selectivities in Mannich and cross-aldol reactions. Notably, complex 3 bearing the labile thiophene carboxylate ligand gave high yields with a diastereomer ratio (d.r.) as high as 1:99 for the direct Mannich reactions of benzaldehyde, cyclohexanone and aniline. In cross-aldol reaction of benzaldehyde and cyclohexanone, 1 and 2 successfully catalyzed the formation of double-aldol products in up to 99 % yield.