Structural and spectral characterization of Cu(II) complexes of N(4)-substituted thiosemicarbazones derived from 2-hydro
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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 E B SEENAa,b, M SITHAMBARESANc, SUNI VASUDEVANd and M R PRATHAPACHANDRA KURUPa,e,* a Department
of Applied Chemistry, Cochin University of Science and Technology, Kochi 682 022, Kerala, India b Post Graduate and Research Department of Chemistry, Maharaja’s College, Ernakulam, India c Department of Chemistry, Eastern University, Chenkaladi, Sri Lanka d Department of Chemistry, National Institute of Technology Calicut, Calicut 673 601, Kerala, India e Departmentof Chemistry, School of Physical Science, Central University of Kerala, Tejaswini Hills, Periye, Kasaragod 671 320, Kerala, India E-mail: [email protected]; [email protected] MS received 1 May 2020; revised 11 August 2020; accepted 17 August 2020
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]C2¯ H5OH(H2O) (5), where the ligand moieties are coordinated as monoanionic (HL) ones. Complexes [CuL12 2 2 dmbipy] (6), [CuL dmbipy]3H2O (7), [CuL bipy]H2O (8) and [CuL phen]2C2H5OH (9) are heterocyclic base adducts. Keywords. 2-Hydroxyacetophenone; thiosemicarbazone; X-ray crystallography; copper(II) complex; EPR spectrum.
1. Introduction Thiosemicarbazones form a class of versatile nitrogen and sulfur (NS) donor chelating ligands and are known to exhibit diverse biological activities.1 The biological activities are dependent upon the chemical nature of the moiety attached to the C=S carbon atom. They can act as tridentate ligands if additional donor atoms are present near the thiosemicarbazone moiety.2 Thiosemicarbazones derived from 2-hydroxyacetophenone can act as a dianionic tridentate ligand by deprotonation of both phenol and thiol functions.2
They can also behave as monoanionic tridentate ligands coordinating with a metal centre through the deprotonated phenolic oxygen, thione sulfur and the azomethine nitrogen.2 Thiosemicarbazones form complexes with copper(II) exhibiting interesting structures.3 Thiosemicarbazones and their copper complexes are of considerable interest because of their chemical and promising b
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