Similar absorption and PL behaviour, at slightly higher wavelengths of 455 and 477 nm, respectively, is observed for tBr-DiKTa (Figure ). A key difference between solution-state and solid-state PL (i.e. in mCP) is that intermolecular (homo-or hetero-molecular) interactions are stronger in the solid state and contribute to the observed emission broadening. Without the steric shielding of the mesityl groups, it is unsurprising that dBr-tBu-DiKTa interact more compared to Mes3-DiKTa, resulting in a slightly broader and red-shifted emission. tBr-DiKTa, which does not contain any sterically bulky groups, appears to interact the most, obvious from the strongest impacts on its PL spectrum.