Replacement of the methyl groups on the acridan with a spiro adamantyl unit, as in a-DMAc-TRZ (λPL: 479 nm; FPL: 86.1%; τd: 4.09 µs in 20 wt% DPEPO; ΔEST: 0.20 eV) results in a blue-shifted emission, but with otherwise comparable photophysical properties to that of DMAC-TRZ (λPL: 495 nm; FPL: 90%; τd: 1.9 µs; ΔEST: 0.05 eV; in 8 wt% mCPCN). The introduction of the rigid and bulky adamantanyl moiety not only suppresses the geometry relaxation in the excited state, but also induced the formation of quasi-axial conformer (QAC) and quasi-equatorial conformer (QEC) geometries corresponding to a shoulder emission peak at around 419 nm and a main emission peak at around 479 nm in the PL spectrum, respectively.