Closely diffusing O–H, amide N–H and methylene C–H oscillators quench the excited state of europium comlexes in solution

In octadentate complexes of europium(III) based on 1,4,7,10-tetraazacyclododecane, deuteriation studies and measurements of excited state lifetimes in solution reveal that amide N–H and methylene C–H oscillators afford an intramolecular vibronic deactivation pathway of the excited Eu 5D0 emissive state which, coupled with a reassessment of the effect of intermolecular OH oscillator quenching, allows more accurate estimates of complex solvation state, q, to be made.