Studies on phenoxo-bridged macrocyclic dicopper complexes. EPR spectral behaviour of mixed-valence systems [Cu(II)Cu(I)L]<SUP>+</SUP> and magnetic exchange interaction in complexes [Cu<SUB>2</SUB>L](ClO<SUB>4</SUB>)<SUB>2</SUB>

EPR spectra of two series of electrochemically generated macrocyclic mixed-valence copper complex species [Cu(II)Cu(I)L]+ have been investigated. Complexes belonging to series 1 [Cu2L](ClO4)2 are derived from 6,12,18,24-substituted (H,H,H,H, (a); Me,Me,Me,Me, (b); Pr,Pr,Pr,Pr (c); Ph,Ph,Ph,Ph (d); H,H,Me,Me (e)) macrocycle 7,11,19,23-dimetheno-9,21-dimethyl-1,5,13,17-tetra-azacyclotetracosa-5,7, 9,12,17,19,21,14-octaene-25,26-diol (H2L). Complexes belonging to series 3, [Cu2L](ClO4)2, are related to those of series 1 by replacement of two of the CH=N linkages by---CH2---NH---groups of the segment containing two azomethine linkages having the 6,12-substituents H,H (a); Me,Me (b); Me,Ph (c). In the mixed-valence species derived from 1b-1e and 3a-3c in MeCN or CH2Cl2 solutions the single unpaired electron is localized on one of the metal centres at room temperature on the EPR time scale. Only the species derived from 1a gives a seven-line EPR spectrum at room temperature indicating that the unpaired electron is delocalized over both metal centers. Variable temperature magnetic measurements on complexes 1b and 1c indicate strong antiferromagnetic exchange (-2J = 835 &#177; 5 cm-1 and 806 &#177; 9 cm-1, respectively) in both cases