Evaluation of exchange interaction in binuclear copper(II) chelates of amide-based cyclophanes

Temperature dependence of the electron paramagnetic resonance (EPR) spectra of binuclear Cu(II) complexes with amide-based cyclophanes, Cu-2(bis-EDTAP DN), Cu-2(bis-EDTANAP) and Cu-2(bis-EDTABPE), in 60% methanol (pH ca. 10) h as been studied at a frequency of 9.43 GHz in the temperature range of 77-4 .2 K; the cyclophanes are macrocyclic compounds in which foul amide bonds l ink two ethylenediaminetetraacetate (EDTA) units and two units of the aroma tic diamine 1,4-phenylenediamine (DPN), 1,5-diaminonaphthalene (NAP) or bis (4-aminophenyl) ether (BPE). Exchange integrals found from the EPR measurem ents are ca. 70-105 cm(-1), 22 cm(-1) and J less than or equal to 0, for Cu -2(bis-EDTAPDN), Cu-2(bis-EDTANAP) and Cu-2(bis-EDTABPE), respectively; the sign of J is defined to be positive for antiferromagnetic interaction. The variation of exchange interactions in these compounds is related to the na ture of the bridging organic groups.