Synthesis and characterization of three heptaaza manganese(II) macrocyclic Schiff base complexes containing two 2-pyridylmethyl pendant arms

摘要

Three new Mn(II) bis(pendant arm)-macrocy-clic Schiff base complexes, [MnL~n]~(2+)(n = 1,2, 3), have been prepared via cyclocondensation of 2,6-diacetylpyri-dine with three different branched hexadentate amines (3,6-bis(2-pyridylmethyl)-3,6-diazaoctane-1,8-diamine (1), 3,7-bis(2-pyridylmethyl)-3,7-diazanonane-1,9-diamine (2) and 3,8-bis(2-pyridylmethyl)-3,8-diazadecane-l, 10-diamine (3)) in the presence of MnCl2 in methanol. The ligands, L, are 15-, 16- and 17-membered pentaaza macrocycles having two 2-pyridylmethyl pendant arms [L~1; 2,13-dimethyl-6,9-bis(2-pyridy lmethyl)-3,6,9,12,18-pentaazabicyclo[ 12.3.1] octadeca-1(18), 2, 12, 14,16-pentaene, L~2; 2,14-dimethyl-6,10-bis(2-pyridylmethyl)-3,6,10,13,19-pentaazabicyclo [13.3.1]nonadeca-1(19),2,13,15,17-pentaeneand L~3;2,15-dimethyl-6,11 -bis(2-pyridylmethyl)-3,6,11,14,20-pentaaz-abicyclo[14.3.1]eicosa-l(20),2,14,16,18-pentaene]. All the complexes have been characterized by physicochemical and spectroscopic methods. The crystal structure of [MnL~1]-(ClO4)2·CH3CN has been determined and indicates that in the solid state, the complex adopts a slightly distorted pentagonal bipyramidal geometry with the Mn(II) centre located within a pentaaza macrocycle with two 2-pyridylmethyl pendants coordinating in the axial positions.