However, DMAC-py-TRZ undergoes a significant geometric reorganization from the bent geometry in the ground state to the orthogonal geometry in the excited state. Spectra collected in a glassy 2-MeTHF matrix at 77 K (Figure ) shed further light on the geometrical relaxation of DMAC-py-TRZ upon photoexcitation. In the frozen matrix, the emission peaks at 404 nm, blue-shifted compared to that in liquid 2-MeTHF at ambient conditions (lPL = 596 nm, Table and Figure ). Apparently, in the frozen matrix the excited compound cannot relax, so that emission occurs from the bent structure and hence peaks at much higher energy than in the (non-polar) liquid solvent. The gated signal collected in the glassy matrix (red line in Figure ) is ascribed to phosphorescence, suggesting a large DEST for this conformer under these conditions, again in line with that calculated for the bent structure.