摘要
A series of copper(II) complexes of C-meso-1,5,8,12-tetramethyl-1,4,8,11-tetraazacyclotetradecane L 1 have been synthesized and characterized. The crystal structure of [CuL 1 (ClO 4 )]ClO 4 1 showed the macrocyclic ligand in the unstable trans-II configuration, while those of [CuL 1 (N 3 ) 2 ] 2 and [CuL 1 (H 2 O) 2 ]X 2 (X = NO 2 3, Cl 4, Br 5 or I 6) showed the macrocyclic ligand to be in the stable trans-III configuration. The metal ion is in a tetragonally elongated octahedral geometry in all the complexes. In 1 one of the perchlorate groups is free while the other bridges two metal ions with two of its oxygen atoms thus forming a linear chain, while in 2 the axial positions are occupied by the nitrogen atoms of two azide groups. The complexes 3-6 are isomorphous. The electronic spectral and the redox properties of the complexes are discussed. The acid dissociation kinetics of 1 has been studied in the temperature range 25.0 ± 0.1 to 45 ± 0.1°C in aqueous HNO 3 -NaNO 3 solutions (I = 5.0 M). The complex exhibited a first order dependence on the hydrogen ion concentration with k obs = k 1H [H + ] + k 1d where k 1H = 2.66 × 10 -5 M -1 s -1 and k1d = 5.54 × 10 -5 s -1 at 25.0 ± 0.1°C. The temperature dependence of the rate constant for the reaction gave ΔH ‡ 1H = 64.7 kJ mol -1 and ΔS ‡ 1H = -117 J K -1 mol -1 for k 1H while for k 1d the parameters are ΔH ‡ 1d = 27.4 kJ mol -1 and ΔS ‡ 1d = -234 J K -1 mol -1 . A possible mechanism of the reaction is discussed. © The Royal Society of Chemistry 1999.