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

Abstract

The Zn 2+ and Cu 2+ 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 Zn 2+ in CH 3CN, 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 Cu 2+ in CH 3CN, the fluorescence emission of L 2 decreased linearly to 80% of its initial value.