We demonstrate how highly emissive, kinetically stable complexes can be prepared using the macrocyclic scaffold of DO3A bearing coordinating aryl ketones as highly effective sensitizing chromophores. In the europium complexes, high quantum yields (up to 18% in water) can be combined with long-wavelength excitation (370 nm). The behavior in solution upon variation of pH, studied by means of UV–vis absorption, emission, and NMR spectroscopies, reveals that the nature of the chromophore can give rise to pH-dependent behavior as a consequence of deprotonation adjacent to the carbonyl group. Knowledge of the molecular speciation in solution is therefore critical when assessing the luminescence properties of such complexes.

A kinetically stable Eu(III) complex for the detection of sulfide in water is reported. The probe shows excellent selectivity and fast reaction time. Its long-lived luminescence makes this the first probe for the time-gated detection of sulfide in complex biological samples.

A kinetically stable Eu(III) complex for the detection of sulfide in water is reported. The probe shows excellent selectivity and fast reaction time. Its long-lived luminescence makes this the first probe for the time-gated detection of sulfide in complex biological samples.