Structural and spectral characterization of Cu(II) complexes of N(4)-substituted thiosemicarbazones derived from 2-hydroxyacetophenone: Crystal structure of a dinuclear Cu(II) complex

Abstract

Copper(II) complexes of 2-hydroxyacetophenone-N(4)-cyclohexylthiosemicarbazone (H2L1) and 2-hydroxyacetophenone-N(4)-phenylthiosemicarbazone (H2L2) have been synthesized and characterized by different physicochemical techniques like magnetic studies and electronic, infrared and EPR spectral studies. [(CuL1)2] (1) is a dinuclear complex having four coordination around copper(II) with distorted square planar geometry. The two individual dinuclear complexes are interconnected through two bifurcated classical hydrogen bond interactions producing a sheet-like structure along b axis. [(CuL2)2]·1/2H2O (2) also has a dimeric structure. The thiosemicarbazones bind to the metal as dianionic ONS donor ligand in all the complexes, except in the complexes [Cu(HL1)Cl]·2H2O (3), [Cu(HL1)Br]·4H2O (4) and [Cu(HL1)NO3]·C2H5OH(H2O) (5), where the ligand moieties are coordinated as monoanionic (HL¯) ones. Complexes [CuL1dmbipy] (6), [CuL2dmbipy]·3H2O (7), [CuL2bipy]·H2O (8) and [CuL2phen]·2C2H5OH (9) are heterocyclic base adducts. The synthesis and characterization of monomeric and dimeric Cu(II) complexes with 2-hydroxyacetophenone-N(4)-cyclohexyl/phenyl substituted ONS donor ligands is described. It also reports the crystal structure of a novel binuclear Cu(II) complex with oxygen bridging and its interesting coordination. This compound [CuL1]2 is a rare example of copper(II)-thiosemicarbazone complex with oxygen bridging structure.