title: Aggregation emission properties of oligomers based on tetraphenylethylene.
abstract: A series of eight derivatives based on tetraphenylethylene were prepared, and two of these, i.e., 1,1-bis(4-phenylcarbonyl)-2,2-diphenylethylene (2), 1,1,2,2-tetrakis(4-phenylcarbonyl)phenylethylene (4), were characterized crystallographically. Because the rigidity and steric hindrance in the molecular structure enhanced regularly from sample 5 to 8, UV-visible absorption and PL spectra of 5-8 show the transition from aggregation-induced emission (AIE) to aggregation-induced emission enhancement (AIEE) behavior. Solid fluorescence lifetime characterization shows that samples with less steric hindrance and more interaction in or between molecules will result in a short fluorescence lifetime. All samples 5-8 become more emissive when their chains are induced to aggregate by adding water into their acetonitrile solutions. Cyclic voltammetry measurements taken give the band gap of sample 5-8 as 2.88, 2.70, 2.56, and 2.43 eV, and theoretical calculations also support these bad gap results. Conformational simulations also suggest that the origin of transition from AIE to AIEE behavior is due to the restricted intramolecular rotations of the aromatic rings in samples.
authors.affiliation: Key Laboratory of Molecular Engineering of Polymers of Ministry of Education, Department of Macromolecular Science, Fudan University, Shanghai 200433. wzwang@ntu.edu.sg
authors.forename: Weizhi
authors.initials: W
authors.lastname: Wang
authors.forename: Tingting
authors.initials: T
authors.lastname: Lin
authors.forename: Min
authors.initials: M
authors.lastname: Wang
authors.forename: Tian-Xi
authors.initials: TX
authors.lastname: Liu
authors.forename: Lulu
authors.initials: L
authors.lastname: Ren
authors.forename: Dan
authors.initials: D
authors.lastname: Chen
authors.forename: Shu
authors.initials: S
authors.lastname: Huang