Rodrigues ACB, Seixas de Melo JS. Aggregation-Induced Emission: From Small Molecules to Polymers-Historical Background, Mechanisms and Photophysics.
Top Curr Chem (Cham) 2021;
379:15. [PMID:
33725207 DOI:
10.1007/s41061-021-00327-9]
[Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Accepted: 02/12/2021] [Indexed: 12/26/2022]
Abstract
The enhancement of photoluminescence through formation of molecular aggregates in organic oligomers and conjugated organic polymers is reviewed. A historical contextualization of aggregation-induced emission (AIE) phenomena is presented. This includes the loose bolt or free rotor effect and J-aggregation phenomena, and discusses their characteristic features, including structures and mechanisms. The basis of both effects is examined in key molecules, with a particular emphasis on the AIE effect occurring in conjugated organic polymers with a polythiophene (PT) skeleton with triphenylethylene (TPE) units. Rigidification of the excited state structure is one of the defining conditions required to obtain AIE, and thus, by changing from a flexible ground state to rigid (quinoidal-like) structures, oligo and PTs are among the most promising emerging molecules alongside with the more extensively used TPE derivatives. Molecular structures moving away from the domination of aggregation-caused quenching to AIE are presented. Future perspectives for the rational design of AIEgen structures are discussed.
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