Formation of 3D networks by H-bonding from novel trinuclear or 1D chain complexes of zinc(II) and cadmium(II) with isonicotinic acid analogues and the effects of π-π stacking

The reactions of isonicotinic acid analogues, 4-quinolinecarboxylic acid (HL1) and 9-acridinecarboxylic acid (HL2) with M(NO3)(2) (M = Zn-II and Cd-II) in the presence of Et3N in MeOH (or EtOH) led to the formation of four new complexes, [Zn(L-1)(2)(H2O)](infinity) (1), [Zn(L-2)(2)(MeOH)(2)](3)center dot(H2O)(1.5) (2) and [Cd(L-2)(2)(MeOH)(2)](3)center dot(H2O)(1.5) (3) and [Cd(L-2)(2)(EtOH)(2)](3)center dot(H2O)(0.5) (4). Single crystal X-ray diffraction analyses revealed that the Zn-II and Cd-II complexes of the same ligand (L-1 or L-2) are isostructural, with 1 taking a 1D chain structure, with 2-4 being trinuclear complexes. In such complexes, the carboxylate groups adopt a bidentate syn, syn-bridging coordination fashion to bridge adjacent metal centers. The N donors do not take part in the coordination, but form O-H center dot center dot center dot N hydrogen bonds with the coordinated water or MeOH (or EtOH), leading to the formation of 3D frameworks. The effects of pi-pi stacking and the structural differences between these complexes and those with isonicotinic acid were also discussed.