Nickel(ii) complexes of cyclen- and cyclam-pyridine: topological reorganisations induced by electron transfer

The NiII complexes of cyclen- and cyclam-pyridine (respectively 1-pyridin-2-ylmethyl-1,4,7,10-tetraazacyclododecane and 1-pyridin-2-ylmethyl-1,4,8,11-tetraazacyclotetradecane denoted NiIIL12+ and NiIIL22+) have been isolated and characterised by X-ray diffraction, UV-visible spectroscopy and electrochemical studies for the NiIIL22+ complex. In particular, the NiIIL22+ complex adopts two distinct and stable geometries (type I and V), which mainly differ by the macrocycle configuration. In solution, the isomerisation process between these two configurations is driven by the nickel-centered electron transfer.