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

Copper(II) complexes of 2-hydroxyacetophenone-N(4)-cyclohexylthiosemicarbazone (H 2 L 1 ) and 2-hydroxyacetophenone-N(4)-phenylthiosemicarbazone (H 2 L 2 ) have been synthesized and characterized by different physicochemical techniques like magnetic studies and electronic, infrared and EPR spectral studies. [(CuL 1 ) 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. [(CuL 2 ) 2 ]· 1 / 2 H 2 O ( 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(HL 1 )Cl]·2H 2 O ( 3 ), [Cu(HL 1 )Br]·4H 2 O ( 4 ) and [Cu(HL 1 )NO 3 ]·C 2 H 5 OH(H 2 O) ( 5 ), where the ligand moieties are coordinated as monoanionic (HL ¯ ) ones. Complexes [CuL 1 dmbipy] ( 6 ), [CuL 2 dmbipy]·3H 2 O ( 7 ), [CuL 2 bipy]·H 2 O ( 8 ) and [CuL 2 phen]·2C 2 H 5 OH ( 9 ) are heterocyclic base adducts. Graphic Abstract 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 [CuL 1 ] 2 is a rare example of copper(II)-thiosemicarbazone complex with oxygen bridging structure.