KINETICS OF COORDINATED-BASE-CATALYZED AND FREE-BASE-CATALYZED CONFIGURATIONAL CONVERSIONS OF A TETRAAMINE MACROCYCLIC LIGAND COMPLEX OF COPPER(II)

[[abstract]]In order to investigate the effect of coordinated hydroxide ion and free hydroxide ion in configurational conversion of a tetraamine macrocyclic ligand complex, the kinetics of the blue-to-red interconversion of the copper(I1) complex of meso-5,5,7,12,12,14-hexamethy1-1,4,8,11 -tetraazacyclotetradecane has been examined spectrophotometrically for [OH-] between 1.99 X lo4 and 5.00 M. All the data are satisfactorily fitted by the rate law R = (kIKOHIOH-] + k2KOH[OH-]2)(1 + KOHIOH-])-'([[Cu(tet a)(blue)12+] + [[Cu(tet a)(OH)(blue)]+]), with kl = 5.51 s-I, k, = 0.84 M-' s-I, and KOH = 51.6 M-' at 25.0 OC and ~1 = 5.0 M (NaN03 + NaOH). The AH* and AS* values for kl are 10.8 kcal mol-' and -19.0 eu, respectively. These small AH* and negative AS* values suggest a concerted coordinated-base-catalyzed mechanism in which intramolecular hydrogen bonding, nitrogen inversion, solvation, and ring conformational changes occur. The AH* and AS* values for k, are 22.8 kcal mol-' and 17.5 eu, respectively. These activation parameters are consistent with the desolvation that takes place in the reaction of [Cu(tet a)(OH)(blue)]+ with free hydroxide ion[[fileno]]2010337010026[[department]]化學