Di-aqua-bridged dinuclear Cu(II) isonicotinate adducts using 2,2′-bipyridine and 1,10-phenanthroline

Abstract

Two new diaquo-bridged dicopper(II) complexes are obtained by reacting Cu(II) nitrate with isonicotinic acid and either 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen). They are formulated as [Cu < inf > 2 < /inf > (μ-OH < inf > 2 < /inf > ) < inf > 2 < /inf > (L) < inf > 2 < /inf > (INH) < inf > 2 < /inf > (NO < inf > 3 < /inf > ) < inf > 2 < /inf > ](NO < inf > 3 < /inf > ) < inf > 2 < /inf > where L = bpy (1), phen (2) and INH = zwitterion of isonicotinic acid. Both the complexes were characterized by single crystal X-ray diffraction analysis, variable temperature magnetic susceptibility measurements and EPR spectroscopy. The complexes consist a dinuclear cation, [Cu(OH < inf > 2 < /inf > ) < inf > 2 < /inf > Cu] < sup > +4 < /sup > at its core in which the water molecules function as unsymmetrical bridges between Cu(II) octahedra in the equatorial-axial mode. The variable temperature (3-300 K) magnetic susceptibility measurements suggest weak ferromagnetic coupling in the dicopper(II) cation with 2J = 3.52 and 1.80 cm < sup > -1 < /sup > respectively for 1 and 2. Both compounds give triplet state EPR with similar zero-field splitting parameter, D = 0.034 cm < sup > -1 < /sup > for 1 and 0.038 cm < sup > -1 < /sup > for 2.