Synthesis, characterization and magnetostructural correlation studies on three binuclear copper complexes of pyrimidine derived Schiff base ligands

• Published in: Polyhedron 2008-08, Vol.27 (12), p.2519-2528
• Main Authors: Gupta, Samik, Pal, Sachindranath, Barik, Anil Kumar, Hazra, Arijit, Roy, Somnath, Mandal, Tarak Nath, Peng, Shie-Ming, Lee, Gene-Hsiang, Salah El Fallah, M., Tercero, Javier, Kar, Susanta Kumar
• Format: Article
• Language: English
• Subjects: Antiferromagnetic; Binuclear copper(II) complex; Ferromagnetic; Magnetostructural correlation; Pyrimidine derived Schiff base ligands
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2008.05.009

Two Schiff base ligands (HL 1 and HL 2) which are closely related in their donor environment only differing at one donor center (O versus S) have been utilized to synthesize a bis(μ-thiolato) and a bis(μ-phenoxo) binuclear Cu(II,II) complex( 1 and 2) respectively. These two complexes are found to vary appreciably in their magnetic properties despite their structural similarities. Ligand HL 2 has been found to adapt well enough to form the (μ-4,4′-bipyridyl) Cu(II,II) binuclear complex ( 3). Three binuclear Cu(II) complexes of two pyrimidine derived Schiff base ligands, 2- S-methyl-6-methyl-4-formyl pyrimidine- N(4)-ethyl thiosemicarbazone (HL 1) and salicyl hydrazone of 2-hydrazino-4,6-dimethylpyrimidine (HL 2), have been prepared. HL 1 produces a bis(μ-thiolato) Cu(II) complex co-crystallizing with its mononuclear analog, [Cu 2(L 1) 2(NO 3) 2][Cu(L 1)(NO 3)] ( 1). On the other hand HL 2 shows versatility by producing two different classes of binuclear Cu(II) complexes, a bis(μ-phenoxo) complex [Cu 2(L 2) 2(NO 3) 2] ( 2) and another a (μ-4,4′-bipyridyl) complex, [Cu 2(L 2) 2(μ-4,4′-bipyridyl)(NO 3) 2] ( 3) under suitable conditions. All the three complexes show distorted square pyramidal geometry around each Cu atom but to a varied extent. Magnetic behavior of complex 1 shows that it is strongly ferromagnetic in nature whereas compounds 2 and 3 are weakly antiferromagnetic in nature. A magnetostructural correlation study combined with molecular modelling on complexes 1 and 2 has thrown light on the difference on magnetic interaction between the Cu atoms in these two complexes. Various factors that may be responsible for such differences are also explored. A novel and potentially useful pH dependant conversion of 3 to 2 has also been noticed.