Spectroscopic and electrochemical properties of group 12 acetates of di-2-pyridylketone thiophene-2-carboxylic acid hydrazone (dpktch-H) complexes. The structure of [Cd(η3-N,N,O-dpktch-H)2]

The reaction between [dpktch] and [M(OAc)(2)] (M = group 12 metal atom) in refluxing CH3CN gave [M(eta(2)-O,O-OAc)(eta(3)-N,N,O-dpktch-H)center dot nH(2)O (n = 0 or 1). The infrared and H-1 NMR spectra are consistent with the coordination of [eta(2)-O,O-OAc] and [eta(3)-N,N,O-dpktch-H](-) and the proposed formulations. The electronic absorption spectra of [M(eta(2)-O,O-OAc)(eta(3)-N,N,O-dpktch-H)]center dot nH(2)O measured in non-aqueous solvents revealed a highly intense intra-ligand-charge transfer (ILCT) transition due to pi-pi* of dpk followed by dpk -> thiophene charge transfer. The electronic transitions of [M(eta(2)-O,O-OAc)(eta(3)-N,N,O-dpktch-H)]center dot nH(2)O are solvent and concentration dependent. Spectrophotometric titrations of dmso solutions of [M(eta(2)-O,O-OAc)(eta(3)-N,N,O-dpktch-H)]center dot nH(2)O with benzoic acid revealed irreversible inter-conversion between [M(eta(2)-O,O-OAc)(eta(3)-N,N,O-dpktch-H)]center dot nH(2)O and it conjugate acid [M(eta(2)-O,O-OAc)(eta(3)-N,N,O-dpktch-H)]center dot nH(2)O pointing to ligand exchange between the acetate and benzoate anions. When CH2Cl2 solutions of [M(eta(2)-O,O-OAc)(eta(3)-N,N,O-dpktch-H)]center dot nH(2)O were titrated with dmso, changes appeared pointing to solvolysis or ligand exchange reactions. Electrochemical measurements on dmso solutions of [M(eta(2)-O,O-OAc)(eta(3)-N,N,O-dpktch-H)]center dot nH(2)O divulged irreversible redox transformations consistent with electrochemical decomposition of [M(eta(2)-O,O-OAc)(eta(3)-N,N,O-dpktch-H)]center dot nH(2)O. The solid state structure of a single crystal of [Cd(eta(3)-N,N,O-dpktch-H)(2)] obtained from a dmso solution of [Cd(eta(2)-O,O-OAc)(eta(3)-N,N,O-dpktch-H)]center dot nH(2)O confirmed the ligand scrambling of [M(eta(2)-O,O-OAc) (eta(3)-N,N,O-dpktch-H)]center dot nH(2)O. The extended structure of [Cd(eta(3)-N,N,O-dpktch-H)(2)] revealed stacks of [Cd(eta(3)-N,N,O-dpktch-H)(2)] locked via a network of hydrogen bonds. A significant amount of empty space (35.5%) was observed in the solid state structure of [Cd(eta(3)-N,N,O-dpktch-H)(2)]. (C) 2015 Elsevier B.V. All rights reserved.