Closely diffusing O-H, amide N-H and methylene C-H oscillators quench the excited state of europium complexes 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.