The influence of the donor-acceptor distance R-L on the photophysical properties, including the emission quantum yield, of two europium complexes with the same coordination number, and thus similar microsymmetries, was investigated by spectroscopic and computational methods. K-3[Eu(dipicCbz)(3)] was synthesized using the new ligand dipicCbz and its photophysical properties compared to Cs-3[Eu(dipic)(3)]. We found that a 50% increase in R-L from 4.1 to 6.5 angstrom results in a substantial decrease in the emission efficiency from 24 to 1.8%.