Lateral macrobicyclic tricompartmental ligands: synthetic, spectral, magnetic, electrochemical and kinetic aspects of binuclear copper(II) complexes

New macrobicyclic tricompartmental ligands and their binuclear copper(II) complexes of type [Cu2L](ClO4)2 have been synthesized from the precursor compound 3,4:10,11-dibenzo-1,13[N,N'-bis(3-formyl-2-hydroxy-5-methyl)benzyl)diaza]-5,9-dioxa-cycloheptadecane with diamines (like ethylene, propylene and butylene) by template method. These complexes have been characterized by IR, UV-Vis spectral studies. Electrochemical studies of binuclear complexes evidence two quasireversible one electrontransfer reduction waves (E-pc(1) = -0.75 to -0.86 V, E-pc(2), = -0.99 to -1.29 V). Room temperature magnetic moment studies convey the presence of antiferromagnetic coupling in binuclear complexes (mu(eff), 1.52 to 1.59 B.M.) which is also observed from the broad ESR spectra with g = 2.11. A variable temperature magnetic susceptibility study of the complex evidences the observed -2J value is 236 cm(-1). The calculated initial rate constant values of catalytic reaction of oxidation of catechol to o-quinone ranges from 0.97 x 10(-2) to 2.30 x 10(-2) min(-1). It is proposed that a distortion of the copper ion geometry arises as the macrocyclic ring size increases. This is supported by spectral, electrochemical and catalytic studies. (C) 2003 Elsevier Science Ltd. All rights reserved.