We investigate an effective model for organometallic complexes (with potential uses in optoelectronic devices) via exact diagonalisation and the configuration interaction singles (CIS) approximation. We demonstrate that increases in the singlet–triplet splitting reduce the radiative rate in such complexes, and that the model correctly predicts the experimental data. We find that for large parameter ranges the CIS approximation accurately reproduces the low energy excitations and hence the photophysical properties of the exact solution. This suggests that electronic correlations do not play an important role in these complexes. This explains why time-dependent density functional theory works surprisingly well in these complexes.