Fig. 11. Illustration of the low-lying singlet and triplet excited states of Au(i) (left) and Au(iii) (right) complexes that accounts for the different photophysical behaviour of the Au(i) and Au(iii) complexes investigated in this work. S1 and T1 for both complexes are derived from HOMO → LUMO transitions; S2 and T4 excited states of 1a are derived from 1,3[H–1 → LUMO] transitions while S3 and T5 excited states of 1b are derived from 1,3[H–2 → LUMO] transitions. The d-orbitals involved in the T2 of 1a and T4 of 1b have the same orientations as their respective S1 excited state (see Tables S5, S6 and S9 in ESI†). The wavy blue arrows indicate internal conversion (IC) from the T5 to T1 excited state. F = fluorescence and P = phosphorescence.
