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

Three binuclear Cu(II) complexes of two pyrimidine derived Schiff base ligands, 2-S-methyl-6-methyl-4-formyl pyrimidine-N(4)-ethyl thiosemicarbazone (HL1) and salicyl hydrazone of 2-hydrazino-4,6-dimethylpyrimidine (HL2), have been prepared. HL1 produces a bis(μ-thiolato) Cu(II) complex co-crystallizing with its mononuclear analog, [Cu2(L1)2(NO3)2][Cu(L1)(NO3)] (1). On the other hand HL2 shows versatility by producing two different classes of binuclear Cu(II) complexes, a bis(μ-phenoxo) complex [Cu2(L2)2(NO3)2] (2) and another a (μ-4,4′-bipyridyl) complex, [Cu2(L2)2(μ-4,4′-bipyridyl)(NO3)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.

Two Schiff base ligands (HL1 and HL2) 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 HL2 has been found to adapt well enough to form the (μ-4,4′-bipyridyl) Cu(II,II) binuclear complex (3).Figure optionsDownload as PowerPoint slide