Dual-Mode Molecular Photoswitches with Multi-Stimulus Response by Introducing Multifunctionality and Eliminating the Heavy Atom Effect

Abstract

The development of new multifunctional smart materials can be significantly advanced by the creation of multi-stimulus-responsive optical switches. However, the design of such switches that can operate in both absorption and emission modes is still a significant challenge. In this paper, we put forward a design strategy for the successful development of a dual-modal molecular photoswitch with multistimulus response. This is achieved by the introduction of multifunctional groups and the elimination of the heavy atom effect. The introduction of photoreactive thiophene groups can effectively activate its photochemical isomerism, thereby exhibiting remarkable photochromic properties. Further oxidation of the thiophene groups endows the photoswitch molecule with efficient fluorescence properties, rendering it a bimodal molecular photoswitch that can be switched by both absorption and fluorescence. The introduction of the protonatable triphenylamine moiety enables the bimodal molecular switch to respond efficiently to protonation, exhibiting dual-stimulus responsive properties. Theoretical analyses have demonstrated that the molecular photoswitch containing a thiophene dioxide group effectively removes the heavy atom effect from the sulfur atom, resulting in bright fluorescence properties. This work pioneers a molecular design strategy that not only mitigates the fluorescence-quenching limitations of thiophene-based photochromes but also integrates dual-stimulus responsiveness, thereby expanding the functionality of photoswitches for cutting-edge applications.