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

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The reactions of isonicotinic acid analogues, 4-quinolinecarboxylic acid (HL1) and 9-acridinecarboxylic acid (HL2) with M(NO3)2 (M = ZnII and CdII) in the presence of Et3N in MeOH (or EtOH) led to the formation of four new complexes, [Zn(L1)2(H2O)]∞ (1), [Zn(L2)2(MeOH)2]3·(H2O)1.5 (2) and [Cd(L2)2(MeOH)2]3·(H2O)1.5 (3) and [Cd(L2)2(EtOH)2]3·(H2O)0.5 (4). Single crystal X-ray diffraction analyses revealed that the ZnII and CdII complexes of the same ligand (L1 or L2) 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⋯N hydrogen bonds with the coordinated water or MeOH (or EtOH), leading to the formation of 3D frameworks. The effects of π–π stacking and the structural differences between these complexes and those with isonicotinic acid were also discussed.