Synthesis, electrochemical and magnetic properties of new macrocyclic copper(II) complexes derived from 2,6-diacetyl-4-4-methylphenol

A series of binuclear macrocyclic copper(II) complexes [Cu2Lm,n](ClO4)(2). xH(2)O have been prepared in which the two copper(II) ions are placed in tw o geometrically distinct co-ordination environments. The macrocycles with t wo 2,6-bis(iminomethyl)-4-methylphenol entities combined through two differ ent lateral chains, -(-CH2-)-(m) and -(-CH2-)-(n) (m = 2 or 3, n = 2 to 5) were synthesized by stepwise cyclization. Cyclic voltammetry shows the pres ence of two reduction couples: (CuCuII)-Cu-II (CuCuII)-Cu-I and (CuCuI)-Cu- II (CuCuI)-Cu-I. The comproportionation constants, K-com, for the mixed val ence (CuCuII)-Cu-I complexes have been determined electrochemically. The K- com value increases in the order of the macrocycles: (L-2,L-2)(2-)<(L-2,L-3 )(2-)<(L-2,L-4)(2-)<(L-2,L-5)(2-) and (L-3,L-3)(2-)<(L-3,L-4)(2-)<(L-3,L-5) (2-). Cryomagnetic investigations (80-300 K) reveal a moderately strong ant iferromagnetic spin exchange between the copper(II) ions within each comple x (J = -210 to -390 cm(-1)).