The synthesis and spectral properties are reported of a set of four europium(III) complexes containing between one and four 3‐azaxanthone sensitising chromophores. Each complex is based on a macrocyclic cyclen core. The emission and aqueous solution 1H NMR spectral properties are compared, revealing information about the local complex symmetry on the experimental timescale. A C2‐symmetric mono‐cationic complex shows an overall emission quantum yield of 10 % in HEPES buffer and exhibits the best relative stability profile in the presence of a million‐fold excess of added metal salts or EDTA, as indicated by the time‐dependence of overall europium emission, following indirect excitation of the 3‐azaxanthone chromophore.