Dinuclear Blocks Research Articles

Synthesis, characterization, DNA binding ability, in vitro cytotoxicity, electrochemical properties and theoretical studies of copper(II) carboxylate complexes

Four copper(II) carboxylate complexes, namely [Cu2(μ-3,5-dinitrobenzoate-O,O')4(4-(dimethylamino)benzaldehyde)2] (1), [Cu2(μ-benzoate-O,O')4(benzoic acid)2] (2), [Cu2(μ-benzoate-O,O')4(H2O)2] [Cu(benzoate-O,O')2(imz)2].2H2O (3) and [Cu(benzoate-O,O')2(2-Me-imz)2] (4) (imz = imidazole, 2-Me-imz = 2-methyl-imidazole), were synthesized and comprehensively characterized by elemental analysis, spectroscopic methods, single crystal X-ray diffraction, cyclic voltammetry (CV), topological analysis as well as theoretical studies. Single crystal X-ray diffraction revealed that products 1 and 2 are dinuclear paddle-wheel complexes, compound 3 is a co-crystal containing mononuclear and dinuclear blocks, while compound 4 is a mononuclear complex. Hirshfeld surface analysis of the compounds rationalized different types of hydrogen bonds, which also lead to the generation of H-bonded networks in 3 and 4. Their topological analysis disclosed a uninodal 4-connected 2D layer with sql topology in 3 and a uninodal 2-connected 1D chain with 2C1 topology in 4. The interaction of 1–4 with calf thymus DNA was investigated by UV–visible and fluorescence spectroscopy, revealing a moderately strong non-intercalative mode of interaction. In vitro cytotoxicity study of the complexes on HepG2 (human liver hepatocellular carcinoma) cell lines revealed a significant inhibition activity. Electrochemical study of the complexes in CH3CN (1–3) and DMSO (4) solution showed a one electron transfer corresponding to Cu(III)Cu(II)/Cu(II)Cu(II) and Cu(II)Cu(II)/Cu(I)Cu(II) redox couples. The ΔE and Ipa/Ipc values suggest that the redox couples are quasireversible. The DFT study was performed to further rationalize the crystal structures and nuclearity of the obtained copper(II) complexes.

Cu II2L based polymeric ladder using dicyanamide bridges: Synthesis, crystal structure and magnetic studies

The reaction in methanol medium of Cu(NO 3) 2·2.5H 2O with H 3L 1 (H 3L 1 = 2-(5-bromo-2-hydroxyphenyl)-1,3-bis[4-(5-bromo-2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) and sodium dicyanamide, Na(dca), in 2:1:1 molar ratio, afforded [Cu 2(L 3)(dca) 2] n ·H 2O·1.5MeOH ( 1). The crystal structure of 1 proves that it is a polymeric complex containing the dianion of the linear hexadentate Schiff base H 2L 3 (H 2L 3 = N, N′-bis(5-bromo-salicylidene)-triethylentetramine). Therefore, this demonstrates that the central imidazolidine ring of H 3L 1 suffered hydrolysis during the reaction, with the consequent cleavage of the central salicylaldehyde residue. The complex so formed shows the linear Schiff base ligand (L 3) 2− with an unusual dinucleating ONN + NNO bistridentate donor behaviour, where both tridentate compartments are anti positioned, and each dca anion is μ-1,5-η 1:η 1 coordinated. This combination results in a ladder-like polymer based on dinuclear blocks. The voids formed between ladders in the crystalline structure trap some methanol and water solvates by means of H bonds. In addition, the magnetic characterisation of 1 demonstrated that the copper(II) ions are weakly coupled, showing an overall antiferromagnetic behaviour.

Controlled synthesis, structures and properties of one-, two-, and three-dimensional lanthanide coordination polymers based on (8-quinolyloxy)acetate

Hydrothermal reactions of Ln(NO3)3 and (8-quinolyloxy)acetic acid (HQOA) with auxiliary ligands resulted in a series of new one-, two- and three-dimensional (1D, 2D and 3D) coordination polymers, namely, [Ln(QOA)2 (H2O)2]·NO3·H2O [Ln = Eu (1), Gd (2)], [Ln2(QOA)4(ox)(H2O)]·3H2O [Ln = Pr (3), Er (4)], [Ln2(QOA)4(BDC) (H2O)]·4H2O [Ln = Sm (5)] and [Ln(QOA)(BDC)] [Ln = Sm (6), Eu (7)] [QOA = (8–quinolyloxy)acetate; ox = oxalate; BDC = 1, 4–benzenedicarboxylate], respectively. Compounds 1–2 possess 1D zigzag chains bridged by QOA anions and 3–4 contain 1D folded chains alternately bridged by oxalates and QOA anions. Complex 5 is an ordered (2,4)–connected 2D sheet-like structure. In compounds 6–7, four BDC anions bridge two adjacent metal atoms to form dinuclear lanthanide building blocks and these dinuclear blocks are further connected together to form an 8-connected 3D network. The progressive variation from 1D zigzag chains (1–2) to 1D folded chains (3–4) to a 2D layer network (5) and to 3D frameworks (6–7) is mainly attributed to the change of bridging ligands as well as the different coordination modes of organic carboxylic ligands. Moreover, the thermal stabilities and photoluminescent properties of these compounds show a remarkable difference due to the progressive variation of crystal structures.