Aggregation-Induced Emission in the Crystals of 9,10-Distyrylanthracene Derivatives: The Essential Role of Restricted Intramolecular Torsion

We have studied the crystal structures and photophysical properties of four 9, 10-distyrylanthracene (DSA) derivatives. Their crystal structures exhibit nonplanar conformations due to the supramolecular interactions resulting in rigid molecules and relative tight stacking. The four DSA derivatives possess a typical aggregation-induced emission (AIE) property, i.e., they exhibit faint emission in their solutions but intense emission in their crystals as a result of the dominant nonradiative decay by free intramolecular torsion in the solution and the restricted torsional motion by supramolecular interaction in the crystal. The investigation of the relationship between the crystal structures and AIE properties of the four DSA derivatives indicates that DSA moiety is the key factor of AIE property because of the restricted intramolecular torsion between the 9, 10-anthrylene core and the vinylene moiety.