Quinoxaline sensitised lanthanide ion luminescence:: Syntheses, spectroscopy and X-ray crystal structure of Na{1,4,7-tris[(N-diethyl)carbamoylmethyl]-1,4,7,10-tetraazacyclododecane-10-(2-methylquinoxaline)}I3 C7H8

The synthesis of a quinoxaline-appended aza-macrocyclic ligand together with corresponding Ln(III) complexes are described. The luminescence properties of the complexes show that the quinoxaline unit sensitises both visible (Eu-III) and near-IR (Nd-III and Yb-III) emitting lanthanide ions. UV-Vis absorption and time-resolved photophysical studies together with X-ray structural data suggest that as well as contributing chromophorically, the quinoxaline moiety generally participates in the first coordination sphere of Ln(III). The luminescent pH response of the Eu-III complex is also reported. The form of the steady state spectrum changes profoundly in the pH range 2-12, implying a change in the coordination environment, which was confirmed with time-resolved lifetime measurements that suggest an increase in europium inner sphere hydration at acidic pH. (C) 2008 Elsevier Ltd. All rights reserved.