Along this molecular chain, the relative transverse and longitudinal shift are 3.02 and 1.32 Å in the DPND6 crystal, whereas they become 0.85 and 1.59 Å in the DPND crystal. Moreover, the intermolecular distances between two monomers are also different and they are 3.22 and 3.34 Å in DPND6 and DPND crystals, respectively. These obvious stacking discrepancies may lead to different spectral characteristics and dynamics processes.