Controllable Secondary through-Space Interaction and Clusteroluminescence of Multiaryl-Substituted Alkanes

Nonconjugated clusteroluminogens (CLgens) become increasingly important in photophysics and advanced bioelectronic applications. Most CLgens show ultraviolet emission, and it remains an enormous challenge to change the electronic structures of CLgens to improve their photophysical properties by precisely regulating the intramolecular through-space interactions (TSI). Herein we propose a general strategy to construct a higher-level intramolecular TSI in multiaryl-substituted alkanes, namely the secondary through-space interaction (2nd TSI), which is constructed by the primary through-space interaction (1st TSI) and TSI linker. By introducing methyl and phenyl into 1,1,3,3-tetraphenylpropane (TPP) respectively, butane-1,1,3,3-tetrayltetrabenzene (Me-TPP) and propane-1,1,1,3,3-pentaylpentabenzene (Ph-TPP) both show bright visible clusteroluminescence (CL), whose fluorescence quantum yield is up to ~40% and the emission wavelength extends to 530 nm. Advanced theoretical studies relating to their emission mechanism are quantitatively performed to analyze the photophysical properties of these CLgens in different states. It is found that molecular rigidity and proper conformation both play pivotal roles in improving the 1st TSI, enhancing the TSI linker and constructing 2nd TSI. Experimental and calculation results prove that the hierarchical TSIs and CL have been successfully regulated in these multiaryl-substituted alkanes (MAAs). This work not only provides a feasible strategy to achieve controllable manipulation of TSI and CL but also paves the way to the in-depth mechanistic understanding of CL.