Structural, spectral, magnetic and thermal studies of 5-(thiophene-2-ylmethine azo) uracil metal complexes

Abstract

Mono- and bimetallic 5-(thiophene-2-ylmethine azo) uracil complexes were prepared in a pure ethanol or ammoniacal solution. The complexes were characterized by elemental analyses, thermal analyses, magnetic moment and spectroscopic measurements. The infrared and 1H-NMR studies revealed that the ligand reacts with all metal ions in a neutral keto form. Also, the ligand behaves as a tridentate or bidentate and coordinated with metal ions by ONS, NS and ON donors atoms, where azomethane nitrogen atom, and/or sulfur atom of thiophene ring and oxygen atom of uracil ring are participated to construct mononuclear Co(II), Ni(II), Zn(II), bimetallic Cd(II); mononuclear Cu(II) and Mn(II) complexes, respectively. However, in case of bimetallic Co(II) 7 and Ni(II) 8 ammine complexes, the ligand bridge is considered to indicate the ligand has tetra- and pentadentate character toward two metal ions, respectively. The magnetic moment values and the Nujol mull electronic spectra showed that all complexes have an octahedral geometry, except Cu(II) complex, 4 has a square planar structure. All the thermal decomposition processes led to formation of metal oxides. The hydrated complexes displayed a higher thermal stability than that of ammine complexes. Theoretical investigations have also been carried out at CAM-B3LYP/LANL2DZ to study the structure of the ligand and its Mn(II) complex. The results confirmed the experimental discussion.