Dinuclear nickel complexes of divergent Ni center dot center dot center dot Ni separation showing ancillary ligand addition and bio-macromolecular interaction

作者：Mahapatra Tufan Singha; Chaudhury Susmitnarayan; Dasgupta Swagata; Bertolasi Valerio; Ray Debashis^*

来源：New Journal of Chemistry, 2016, 40(3): 2268-2279.

DOI：10.1039/c5nj02410b

Schiff base ligand HL has been utilized to build up a new family of five [Ni-2] complexes, [Ni-2(mu-L)(mu-OH)](ClO4)(2) [1(ClO4)(2)], [Ni-2(mu-L)(m-CF3CO2)(2)(C3H7NO)(H2O)]CF3CO2 center dot H2O[2a(CF3CO2)center dot H2O], [Ni-2(mu-L)(mu-CH3CH2CO2) (2)(C3H7NO)(H2O)]ClO4 center dot C3H7NO[2b(ClO4)center dot C3H7NO], [Ni-2(mu-L)(mu-CH3CO2)(mu-NCS)(NCS)(C3H7NO)] (3a) and [Ni-2(mu-L)(mu-CH3CO2)(mu-N-3)(N-3)(C3H7NO)] (3b), in varying co-ligand environments. All the complexes have been characterized by elemental analyses, X-ray structure analysis and spectroscopic measurements. Three distinct types, dicationic, monocationic and neutral complexes, are synthesized using one pentadentate ligand HL. The Ni-II centers are bridged by three sets of bridging groups resulting in a wide variation in Ni center dot center dot center dot Ni separations from 2.897 to 3.475 angstrom. Doubly bridged Ni-II centers in the edge-shared square planar environment provide the shortest Ni center dot center dot center dot Ni separation in 1(2+). Whereas combination of other bridges from carboxylate, azide and isothiocyanate ancillary ligands results in cationic and neutral [Ni-2] complexes 2(+) and 3 having longer intermetallic separations. Modulation of Ni center dot center dot center dot Ni separation in synthetic complexes is fascinating in relation to the involvement and stabilization of the dinickel motif in the catalytic transition state of urease. Interaction and binding of cationic complexes (1-2b) with human serum albumin (HSA) and calf thymus-DNA have been examined using spectroscopic techniques. Tryptophan fluorescence quenching of HSA by cationic bimetallic complexes (1, 2a and 2b) featuring a hydrophobic ligand environment shows spontaneous and favorable interactions in the order of 2a > 2b > 1. For the interaction study with CT-DNA, nearly planar complex 1 binds more efficiently than 2a and 2b in octahedral coordination geometry.

• 出版日期2016