Synthesis and structure of copper(II) complexes: Potential cyanide sensor and oxidase model

The new complexes of compositions [(L a ) 2 Cu] and [(L b ) 2 Cu] were prepared by treating with 2-hydroxy-5-methyl-3-(2-aryldiazenyl)phenylimino) methyl) benzaldehyde (HL a ) and ethyl-2-cyano-3-(2-hydroxy-5-methyl-3-(-(2-aryldiazenyl) phenylimino) methyl) phenyl) acrylate (HL b ) ligands [where aryl is phenyl for HL _a^ 1 and HL _b^ 1 ; p -methyl phenyl for HL _a^ 2 and HL _b^ 2 ; and p -chloro phenyl for HL _a^ 3 and HL _b^ 3 ] with Cu(OAc) 2 .H 2 O, respectively. Both the bis copper(II) complexes consist of tridentate (N,N,O) anionic ligands, L _a^ - or L _b^ - . X-ray structures of the representative complexes [(L _a^ 1)_2 Cu] and [(L _b^ 2)_2 Cu] were determined to confirm the molecular species unequivocally. The molecular structure of copper complexes exhibited tetragonally distorted (Jahn-Teller) geometry consistent with the d 9 configuration of Cu(II) metal ion. Oxidation of benzyl alcohols using the newly synthesized complexes as catalyst has been studied. Photoluminescence properties of [(L _a^ 2)_2 Cu] and [(L _b^ 2)_2 Cu] were exploited for selective cyanide recognition. The [(L b ) 2 Cu], complexes displayed antibacterial activity toward gram positive and gram negative bacteria. Graphical Abstract Newly synthesized Cu(II) complexes exhibited fascinating changes in the emission property upon addition of cyanides, selectively. The catalytic activity toward oxidation of benzyl alcohol corroborated the new complexes as potential oxidase model.