Nonconventional Macromolecular Luminogens with Aggregation-Induced Emission Characteristics

Nonconventional luminogens without classic conjugated structures have drawn increasing interests owing to their fundamental importance and promising applications. These luminogens generally bear such subgroups as tertiary amine, C=C, C N, C=O, OH, ether, and imide. The emission mechanism, however, remains under debate. Different assumptions like oxidation or acidification of tertiary amines, aggregation of C=O groups, as well as clustering and electron cloud overlap are proposed. Unlike concentration quenching and aggregation-caused quenching (ACQ) that are normally observed in traditional luminogens, many of these unorthodox luminogens exhibit unique aggregation-induced emission (AIE) characteristics, regardless of their molecular architectures. This review summarizes varying unorthodox luminogens with AIE features, aiming to outline the recent advances in this exciting area, with focus on the macromolecular systems. In light of the reported results, clustering-triggered emission mechanism, namely clustering of diverse subgroups with subsequent electron cloud overlap and conformation rigidification can well rationalize the photophysical behaviors of most systems. (C) 2016 Wiley Periodicals, Inc.