Self-assembling of three rare structurally various homomultinuclear Cu^II complexes derived from a bis(salamo)-based multioxime ligand

Abstract

A family of rare structurally different homometal multinuclear CuII bis(salamo)-based complexes, [Cu4(L)2(MeOH)2](ClO4)2·2MeOH (1), [Cu4(L)2(EtOH)2](NO3)2·2EtOH (2) and [Cu2(HL)(EtOH)Br2]·CHCl3 (3), has been successfully synthesized by the reactions of cupric salts with a bis(salamo)-based multidentate chelate ligand (H3 L). The salamo-based ligand [R-CH=N—O—(CH2) n —O—N=CH—R] is a new type of salen-based analog. Complexes (1) and (2) are isostructural structures, and crystallize in monoclinic space group P21/n with centrosymmetric spiral structures, where the main structures contain two fully deprotonated ligand (L)3− units, a charged tetranuclear CuII folding center and two coordinated solvent molecules. Complex (3) crystallizes in monoclinic space group Cc and consists of two CuII cations, one incompletely deprotonated ligand (HL)2− unit and one coordinated ethanol molecule, and forms a novel homo-binuclear CuII complex structure due to Br− counter anions. Complexes (1)–(3) have zero-dimensional cluster-based structures and are further assembled into three-dimensional frameworks via intermolecular interactions. Because of the different solvents and counter anions which have a significant influence on the structures of complexes (1)–(3), the interactions were quantitatively evaluated by Hirshfeld surfaces analyses. Complexes (1)–(3) have been characterized by elemental analyses, IR spectra, UV–vis spectra and X-ray crystallography analyses. In addition, fluorescence properties are evaluated and DFT calculations are performed.