Synthesis and spectroscopic studies on novel Cu(II)-Cu(II)binuclear adducts.EPR evidence for ferromagnetic interactions

摘要

EPR investigations on two solid complexes[Cu(1-amidino-O-2-methoxyethylurea)2]2(H2O)2(SO4)2(1)and[Cu(1-amidino-O-2-ethoxyethylurea)2]2(H2O)2(SO4)2(2)indicated the formation of ferromagnetical-ly coupled binuclear complexes(S=1)having the isotropic exchange interaction constant J values of 59 and 50 cm~(-1).The angle between the Cu-Cu direction and the parallel direction(zeta)of the complex 1 has been evaluated.The IR studies suggest the presence of tetrahedral sulfate ion in the complexes.When the EPR spectra were recorded in the temperature range 30O-475 K,it was observed that the triplet-state EPR signal disappeared completely and irreversibly at ca.450 K for complex 1 and at ca.475 K for complex 2 with the appearance of a new signal attributable to the mononuclear complex(S=1/2).