Mono- and bis-N-functionalised cyclen with benzimidazolylmethyl pendant arms: Sensitive and selective fluorescent probes for zinc and copper ions

The Zn2+ and Cu2+ complexes of L-1 and L-2 ligands (L-1: 1-(benzimidazol-2-ylmethyl)-1,4,7,10-tetraazacyclododecane, L-2: 1,7-bis(benzimidazol-2-ylmethyl)-1,4,7,10-tetraazacyclododecane) were synthesised and characterised by means of NMR, EPR, and UV-Vis spectroscopies, X-ray determination and molecular modelisation (HF-DFT(B3LYP)/LANL2DZ). These studies showed that the 1: 1 complexes were formed in which the benzimidazole arm(s) are coordinated to the metal ion. On addition of successive amounts of Zn2+ in CH3CN, the. fluorescence emission of L-1 increased linearly by a factor of 50 and the one of L-2 by a factor of 5 while on addition of successive amounts of Cu2+ in CH3CN, the. fluorescence emission of L-2 decreased linearly to 80% of its initial value. (C) 2008 Elsevier B. V. All rights reserved.