Macrocyclic ligand ring size effects. Part 2. Synthetic, structural and electrochemical studies of the interaction of NiII with 14-membered tetraaza macrocycles containing fused dibenzo substituents

Abstract

A comparative study of the high- and low-spin complexes of Ni^II with two tetraaza dibenzo-substituted macrocycles incorporating 14-membered inner rings has been carried out. The results obtained are also compared with those for the analogous nickel(II) derivatives of 1,4,8,11-tetraazacyclotetradecane. Four X-ray structures of nickel complexes as well as the structure of one free ligand have been determined. These structures taken together with previous X-ray structural data and selected molecular mechanics calculations have enabled a detailed assessment of the effects of spin state and ligand substituent on the hole size and ring conformations adopted by individual complexes. A comparative electrochemical investigation of individual high- and low-spin complexes in the series has been performed.