New macrocyclic Schiff base complexes incorporating a phenanthroline unit: Part 1; Template synthesis of three cadmium(II) complexes and crystal structure, NMR and ab initio studies

Complexes of three Cd(II)-containing macrocyclic Schiff base complexes containing a phenanthroline ligand (L) of the type [CdLn(Cl)]+ (n = 2, 3, 4), have been prepared via [1+1] cyclocondensation of 2,9-dicarboxaldehyde-1,10-phenanthroline and a number of linear triamines via a metal-templated reaction and coordination features have been examined. The ligands, L, are 16-, 17-, and 18-membered pentaaza macrocycles and all the complexes incorporate a 1,10-phenanthroline unit as an integral part of their cyclic structure. The complexes have been characterized by a variety of methods including IR, 1H, 13C, DEPT, COSY(H,H) and HMQC(H,C) NMR studies and MALDI mass spectrometry. The polymeric structure of [CdL2 (Cl)]nn + was determined by X-ray crystallography, which showed that the complex cation consisted of a pentagonal bipyramidally coordinated Cd(II) ion. The seven-coordinated Cd(II) ion is ligated by the five nitrogen atoms of the macrocycle in the equatorial plane and has two bridging chloride ligands in the axial positions resulting in a ribbon of such complex ions. Supporting ab initio HF-MO calculations have been undertaken using the standard 3-21G* and 6-31G* basis sets. © 2006 Elsevier B.V. All rights reserved.