Copper (II) complexes of a macrocyclic binucleating ligand which exhibit two-electron oxidation and two-electron reduction. Structure of [Cu2(C24H34N4O2)(CH3OH)2](ClO4)2, a macrocyclic dicopper(II) complex involving coordinated methanol

The saturated ligand H 2 L1, derived by template condensation of 4-methyl-2,6-diformylphenol and 1,3-diaminopropane, followed by borohydride reduction, generates binuclear, antiferromagnetically coupled, copper(II) complexes which exhibit cyclic voltammetry involving two one-electron oxidation steps (E 1/2  = 1.1 to 1.2 V, 1.3 to 1.4 V; Pt/CH 3 CN/SCE) and two one-electron reduction steps (E 1/2  = −0.75 to −0.76 V, −0.89 to −0.90 V (GC/DMSO/SCE) with the formation of Cu(III)–Cu(III) and Cu(I)–Cu(I) and mixed oxidation state species. A trinuclear derivative, [Cu 2 (L1)(CuCl 4 )], appears to contain a spin-coupled binuclear species bound to a magnetically isolated tetrachlorocuprate(II) entity. The complex [Cu2(L1)(CH 3 OH)2](ClO 4 )2 forms brown crystals with a = 8.6516(7), b = 11.6832(9), c = 16.7205(6) Å, β = 92.596(5)°, P21/ n , Z = 2, R f  = 0.037 and has a copper–copper separation of 3.088(1) Å and two weakly bound trans-axial methanol molecules (Cu—O, 2.413(4) Å). Variable temperature magnetic studies on [Cu 2 (L1)(ClO 4 ) 2 ] and [Cu 2 (L1)](ClO 4 )2 indicate strong antiferromagnetic exchange (−2J = 824 ± 5cm −1 , 827 ± 7cm −1 , respectively) in both cases.