Our main objective is to better understand the spin-spin interaction of dinuclear copper(II) complexes in bridging systems. Four complexes of the type [Cu2(L)4(OR) 2](X)2, where L is 2-amino-4-methylpyrimidine or 2-amino-4-cyanopyridine and X = Cl-, have been synthesized. The title compounds all consist of dinuclear units with OCH3 or O-C2H5 bridging groups. All complexes were synthesized in a one-step reaction, and were characterized by elemental analysis, FTIR, ESR, electronic spectroscopy and by magnetic moment determination. The compounds exhibit antiferromagnetic interactions at room temperature. The UV-Vis spectra show three absorption bands attributed to the dd transition of the copper(II) ion, ligand®metal charge transition (LMCT) and p®p* or n®p* transitions of the ligand. The FTIR spectra exhibit Cu2O2 ring vibrations from 570-410 cm-1. All complexes show room temperature magnetic moments of about 1.32 to 1.54 B.M. per copper atom. The X-band electron spin resonance (ESR) studies indicate a weak half-field band, which is characteristic of the Cu(II)–Cu(II) dimer, observed at about 1600 gauss. The observation of this band strongly suggests that the hyperfine structure arises from a triplet spin species. The spectra of samples in DMF or DMSO frozen at liquid nitrogen temperature show typical Dm = 1 transition.
