The new pentadentate thioether thiolate ligand Et2NpyS42− {= 4‐(diethylamino)‐2,6‐bis[(2‐mercaptophenyl)thiomethyl]pyridine(2−)} has been synthesised from dimethyl 4‐bromopyridine‐2,6‐dicarboxylate by treatment with Et2NH followed by reduction and tosylation. The tosylated product was subsequently used for the template alkylation of [Ni(S2C6H4)2]2− to give [{Ni(Et2NpyS4)}2] (4). Acidic hydrolysis of 4 resulted in the formation of the ligand Et2NpyS4−H2·HCl (5). The dianion Et2NpyS42− reacted with FeCl2·H2O to afford the dinuclear high‐spin species [{Fe(Et2NpyS4)}2] (6) [μeff (297 K) = 5.15 μB]. Aerial oxidation of dinuclear 6 afforded the sulfinato complex [{Fe(Et2NpyS4−O2)}2] (7). Complex 6 proved to be a good precursor for the syntheses of [Fe(L)(Et2NpyS4)] [L = CO (8), CNCy (9), NO (11) and N2H4 (12)] and [Fe(NO)(Et2NpyS4)]BF4 (10). Protonation or alkylation of the thiolate donor atoms resulted in a series of complexes [Fe(CO)(Et2NpyS4−R)]BF4 [R = H (8a), Et (8b)] and [Fe(CO)(Et2NpyS4−Et2)](BF4)2 (8c) but no labilisation of the Fe−CO bond was observed. Only in complex 8 could the CO coligand be exchanged by NO+ to give [Fe(NO)(Et2NpyS4)]BF4 (10). Reduction of 10 using N2H4, NH3 or N3− afforded the 19 valence electron species [Fe(NO)(Et2NpyS4)] (11). [Ru(NO)(Et2NpyS4)]Br (13) was synthesised by template alkylation of Bu4N[Ru(NO)(S2C6H4)2] using Et2Npy(CH2Br)2 (3). Under reducing conditions, 13 releases the NO coligand to give [{Ru(Et2NpyS4)}2] (14), while in the presence of N2H4, [Ru(N2H4)(Et2NpyS4)] (15) was formed. The complexes were well characterised including the solid‐state structures in most cases. X‐ray structural analyses of 7, 8, 9, 10, 12 and 15 revealed that all complexes exhibit trans‐thiolate donors irrespective of the σ−π‐ or σ‐ligand character of L. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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In quest of antimicrobial and anticancer agents, metformin containing Ni (II) complexes, [Ni (Met)2]Cl·OH (1) and [Ni (Met)(IDA)] (2) {Met: metformin, IDA: iminodiacetic acid} were synthesized and X‐ray structure of 1 is four‐coordinate square planar geometry. Bovine serum albumin (BSA) interaction and binding studies to Met, IDA and their Ni (II) complexes were investigated and showed a strong interaction. A static quenching process was proposed at low concentrations of compounds whereas, combined quenching process was observed for 1 and 2 at higher concentrations. Kinetic stability, affinity and association constants of compounds‐BSA were studied using stopped‐flow technique and a mechanism was proposed: a fast and reversible step of BSA binding including complex formation and dissociation was proposed; for the second step, a reversible reaction was observed for 1 and 2 whereas, an irreversible reaction with Met and IDA was observed indicating that coordination with nickel ions change the interaction mechanism. Additionally, the antibacterial investigation against both Gram‐positive and Gram‐negative bacteria showed that all compounds exhibited significant activities. They also show cytotoxicity against HepG2 human liver cancer cell but the half maximal inhibitory concentration (IC50) values obtained for the cell lines were higher in comparison with cisplatin. Although Met‐BSA and IDA‐BSA are kinetically more stable than that of 1‐BSA and 2‐BSA, 1‐BSA and 2‐BSA showed better antibacterial and cytotoxic activities which is in agreement with the binding constants.

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