Then, we explored the molecular and electronic structures of DCzPy by using quantum mechanics/molecular mechanics (QM/MM) model at the TD-MPW1PW91/def2-SVP level to elucidate the pressure-induced structural change (Fig. ), and the dihedral angles among these groups are defined as θ1 (1-2-3-4) and θ2 (1-5-6-7) (Fig. ). Focusing on the DCzPy crystal, the optimized S1 state has an emission wavelength at 498 nm along with dihedral angles of θ1 = 140 o and θ2 = 129 o , reproducing the dominant peak of PL spectra (490 nm) in the experiment. By scanning the θ1 from 120 to 175 o and fixing θ2 = 129 o (Fig. and S18), the excitation energies are gradually blue-shifted from 540 to 460 nm. Such a change can be ascribed to the different Coulomb and exchange interactions, owing to the variation of spatial distance between hole and electron caused by dihedral angle θ1, whereas the charge distributions of hole and electron are almost unchanged (Fig. ). When θ1 increases to 160°, the calculated excitation energy (467 nm) agrees well with the emission peak (457 nm) of DCzPy crystal after gently grinding. Afterwards, we scanned θ2 with a fixed θ1, it is found that the excitation energies are firstly blue-shifted (θ2<145 o ) and then red-shifted (Fig. ). Impressively, the geometry (θ1 = 160 o , θ2 = 160 o ) shows an emission wavelength of 504 nm, attributing to the increased hole distribution on dicyanopyridine group (Fig. ), which is in good agreement with the experimental ones (490 nm) of DCzPy crystal after heavily grinding. Based on these features, it rationally speculated that the structural change of DCzPy can be responsible for the pressure-induced variation in emission peaks.