(Cyclen– and cyclam–pyridine)copper Complexes: The Role of the Pyridine Moiety in Cu^II and Cu^I Stabilisation

Abstract

Abstract The protonation constants of cyclen– and cyclam–pyridine [1‐(pyridin‐2‐ylmethyl)‐1,4,7,10‐tetraazacyclododecane ( L 1 ) and 1‐(pyridin‐2‐ylmethyl)‐1,4,8,11‐tetraazacyclotetradecane ( L 2 ), respectively] and the stability constants (log β 110 ) of the corresponding copper complexes ([Cu L 1 ] 2+ and [Cu L 2 ] 2+ ) were determined by potentiometric titrations. The complexes were subsequently isolated and characterised by X‐ray diffraction, UV/Vis spectroscopy and electrochemical studies. The [Cu L 2 ] 2+ complex adopts two distinct and stable geometries ( trans I and III), which mainly differ by the macrocycle configuration. The trans III configurational isomer can be converted into the trans I one by electron transfer. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)