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)-macrocyclic Schiff base complexes, [MnLn]2+(n = 1, 2, 3), have been prepared via cyclocondensation of 2,6-diacetylpyridine 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-1,10-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 [L1; 2,13-dimethyl-6,9-bis(2-pyridylmethyl)-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18), 2, 12, 14, 16-pentaene, L2; 2,14-dimethyl-6,10- bis(2-pyridylmethyl)-3,6,10,13,19-pentaazabicyclo[13.3.1]nonadeca-1(19), 2, 13, 15, 17-pentaene and L3; 2,15-dimethyl-6,11-bis(2-pyridylmethyl)-3,6,11,14,20-pentaazabicyclo[14.3.1]eicosa-1(20),2,14,16,18-pentaene]. All the complexes have been characterized by physicochemical and spectroscopic methods. The crystal structure of [MnL1](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.