Relationship between Molecular Stacking and Optical Properties of 9,10-Bis((4-N,N-dialkylamino)styryl) Anthracene Crystals: The Cooperation of Excitonic and Dipolar Coupling

Li, Feng Gao, Na Xu, Hai Liu, Wei Shang, Hui [UCL] Yang, Wenjun Zhang, Ming et al.[show all]

Five 9,10-bis((4-N,N-dialkylamino)styryl) anthracene derivatives (DSA-C1–DSA-C7) with different length alkyl chains were synthesized. They showed the same color in dilute solutions but different colors in crystals. The absorption, hotoluminescence, and fluorescence decay indicate that there exist both excitonic and dipolar coupling in crystals of DSA-C1–DSA-C7. X-ray crystallographic analysis revealed that all the crystals belong to the triclinic space group P1¯ with one molecule per unit cell and that the molecules in every crystal have the identical orientation. This offers ideal samples to investigate the impact of the molecular stacking on the optical properties of the crystals. For the first time, the ooperation of excitonic and dipolar coupling has been comprehensively studied, and the contribution to the spectral shift from the excitonic and dipolar couplings quantitatively obtained. The experiments of amplified spontaneous emission (ASE) together with measurements of the quantum efficiency further confirmed this interpretation. The results suggest that the excitonic and dipolar couplings between the adjacent molecules are both important and jointly induce the spectral shifts of the crystals.