摘要
A new difunctionalized tetraaza macrocycle, 1,8-bis(2-hydroxyethyl)-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetrabskpf512 azacyclotetradecane, H 2 L 2 has been synthesized in one step by the reaction of ethylene oxide and C-rac-5,5,7,12,12, 14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (L 1 ). The crystal structure of [Cu(H 2 L 2 )][ClO 4 ] 2 1 shows the metal ion in tetragonally elongated octahedral geometry, co-ordinated by the oxygen atoms of the pendant arms in the trans-axial position. Copper(II) complexes were also synthesized and characterized from other 1,8-disubstituted macrocyclic ligands L 3 , L 4 , HL 5 , H 2 L 6 , L 8 and H 2 L 9 . The molecular structure of [CuL 3 ][ClO 4 ] 2 2 (R 1 = R 2 = CH 2 CH 2 -CN) and [CuL 5 ]ClO 4 , 4 (R 1 = H, R 2 = CH 2 CO 2 - ) shows the macrocycle in trans-I configuration with square planar and distorted square pyramidal geometries respectively at the metal centers. The structures of complexes [CuL 8 ]-[ClO 4 ] 2 6 [L 8 = 1,8-bis(2-cyanoethyl)-4,7,11,14-tetramethyl-1,4,8,11-tetraazacyclotetradecane] and [Cu(H 2 L 9 )][ClO 4 ] 2 7 (corresponding CH 2 CO 2 H derivative) show the macrocyclic ligand in the trans-III configuration. Interestingly the two pendant acetic acid groups of H 2 L 9 in 7 remain protonated and co-ordinate through the carbonyl oxygen atoms in trans-octahedral geometry. The cyclic voltammetric studies of the complexes revealed that the copper(I) oxidation state is highly stabilized by the ligands L 3 and L 8 . The pH dependent co-ordination geometry changes of complexes 4, [CuL 6 ] 5 (R 1 = R 2 = CH 2 CO 2 - ) and 7 based on the changes in their electronic spectra are discussed. The kinetics of acid promoted dissociation reactions of complexes 2 and 6 has been studied in HCl-NaCl solutions (I = 5.0 M). The possible mechanisms of the reactions, the factors influencing the rate and the relative importance of the solvent separation and protonation pathways are discussed.