Influence Of Intermolecular Interactions On Molecular Packing And Photophysical Properties In Polymorphs Of Anthracene Derivatives

Wang et al. have designed and synthesized five luminescent polymorphs by tuning the molecular assembly structures in crystals (Adv.Mater.2006, 18, 2369-2372) which show different colors.In the past, we usually modify of the substitute group to regulate the photo physical properties, whereas the non-covalent intermolecular interactions are able to strongly influence the final packing structure, make polymorphism existence. Polymorph is a solid crystalline phase of a given compound resulting from the possibility of at least two different arrangements of the molecules of that compound in the solid states, which is a widespread phenomenon.Wang et al. have designed and synthesized anthracene derivatives, under specific circumstances, crystals with different colors were achieved, which can be attributed to weak interactions between molecules leading to distinctive aggregation. Different polymorphs base on the same single molecular may have very different physical and chemical properties, and therefore represent special situations for the study of structure-property relationships.To reveal the relationship between different molecular packing and emission colors, theoretical analysis of spectral properties and electronic structures of these complexes were systematically characterized. The geometric and electronic structures of the complexes in the ground state are studied with density functional theory (DFT) ,whereas the lowest singlet excited states are optimized by ab initio CIS. To assign the absorption and emission peaks observed in the experiment, we computed the spectrum of the lowest singlet excited states with time-dependent DFT (TD-DFT). All DFT calculations were performed using the B3LYP functional and the 6-31G* basis set.This work suggests that, the anthracene derivatives accumulate into trimers via hydrogen bonding have a little influence on the shift of the spectra, but can increase the luminous intensity and play the role of supporting the trimer skeleton. At the same time, the intermolecularπ...πinteraction between the organic light-emitting elements has an important impact on the luminescent properties and lead to red shifts of emission spectra.