Impact of cyclic topology: odd–even glass transition temperatures and fluorescence quantum yields in molecularly-defined macrocycles

Abstract

Topological molecular architectures play a crucial role in many physico-chemical properties of materials and biological processes. Herein we synthesized a series of molecularly-defined cyclic oligomers, cyclic-TPE_n+1 (n = 1–6), containing tetraphenylethylene (TPE) segments in the main chain by a stepwise chain-growth strategy. The cyclic structure endows the cyclic-TPE_n+1 with a higher glass transition temperature (T_g) and quantum yields of aggregation induced emission (AIE) for n = 1 and 2 due to the constraints imposed by the cyclic topology itself. Importantly, the cyclic topology induces odd–even effects on both T_g and photoluminescence quantum yield, arising from the alternation of intermolecular interactions. Hopefully, this work will advance our understanding on the glass transition and AIE mechanism, and finally pave the way for the development of luminogens with a wide variety of functions.