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 [Cu2(μ-OH2)2(L)2(INH)2(NO3)2](NO3)2 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(OH2)2Cu]+4 at its core in which the water molecules function as unsymmetrical bridges between Cu(II) octahedra in the equatorial–axial mode. The variable temperature (3–300K) magnetic susceptibility measurements suggest weak ferromagnetic coupling in the dicopper(II) cation with 2J=3.52 and 1.80cm−1 respectively for 1 and 2. Both compounds give triplet state EPR with similar zero-field splitting parameter, D=0.034cm−1 for 1 and 0.038cm−1 for 2.