IJSRSET184970 | Received : 15 July 2018 | Accepted : 30 July 2018 | July-August-2018 [ 4 (9) : 343-347] © 2018 IJSRSET | Volume 4 | Issue 9 | Print ISSN: 2395-1990 | Online ISSN : 2394-4099 Themed Section : Engineering and Technology 343 EPR Spectral Studies of Dimeric and Monomeric Cu(II) Complexes of di-2-pyridyl Ketone N(4)-methyl Thiosemicarbazone Renjusha S. Assistant Professor, Department of Chemistry, N.S.S. College, Pandalam, India ABSTRACT Four copper(II) complexes, [Cu2(DpyMeTsc)2SO4]·3H2O (1), [Cu(DpyMeTsc)N3]·H2O (2), [Cu2(DpyMeTsc)2]·(ClO4)2·2H2O (3), and [Cu(DpyMeTsc)(CH3COO)]·2H2O (4) of di-2-pyridyl ketone N(4)- methylthiosemicarbazone (HDpyMeTsc) are studied with electron paramagnetic resonance (EPR) spectroscopy. EPR is the most powerful spectroscopic method to discriminate between monomeric and dimeric Cu(II) complexes in solution. EPR studies indicate dimeric nature of (1) and (3) and monomeric nature of (2) and (4). Keywords: Thiosemicarbazone; Cu(II) complex; Di-2-pyridyl ketone; EPR spectra. I. INTRODUCTION The coordination chemistry of transition metal complexes involving nitrogen and sulfur donor ligands has been the cynosure among chemists during recent years due to the application of these chelates in modelling of biomolecules, in the field of chemical and biological reactivity and nuclear medicine. The potential role played by copper ions, being present in the active sites of a large number of metalloproteins having the CuN2S2 chromophore, has stimulated efforts to design new ligand frames having nitrogen sulfur donor sites and characterize copper complexes as models for providing a better understanding of the biological system 1 . The activity of thiosemicarbazones depends very much on the parent aldehyde or ketone and is affected also by N(4) substitution 2 . Thiosemicarbazones derived from di-2- pyridyl ketone are potentially tetradentate. However in majority of cases they function as tridentate ligands only. Literature survey reveals that the presence of a metal ion increases the activity of or mitigate the side effects of the parent organic compounds 3 . Copper(II) is a biologically active, essential ion; its chelating ability and positive redox potential allow participation in biological transport reactions. Also, copper(II) forms the active centers of more than a dozen metalloproteins. Further, copper(II) complexes possess a wide range of biological activity and are among the most potent antiviral, antitumor and anti- inflammatory agents 4 . Cu(II) complexes display a wide range of geometric arrangements around the copper ion, from the square planar to deformed tetrahedral geometry. Pseudohalide anions like azides and thiocyanate are found to be versatile ligands in terminal and bridging modes. These phenomena are reflected in their spectral properties. Electron paramagnetic resonance (EPR) is a suitable tool for the study of paramagnetic metal ion complexes and may provide useful information about the oxidation states, modes of coordination, geometry and type of ligand sites 5 .