H-bonding-assisted energy retention in bicyclic diene photoswitches for rechargeable solar thermal batteries: CASSCF, CASPT2, and DLPNO-CCSD(T) insights

Abstract

Molecular solar thermal (MOST) systems have the potential to harness and store a vast amount of solar energy, making them promising for renewable energy solutions. However, the integration of solar absorption, high energy storage density, and long thermal half-life into a single photochromic couple remains a contemporary challenge, hindering their practical deployment. In this work, we present a rational design strategy to enhance key properties of a bridged bicyclic diene (BBD)-based photoswitch through elongation of the unsaturated bridge and strategic functionalization. The introduced substituents promote synergistic non-covalent interactions, particularly intramolecular hydrogen bonding and reinforce push–pull electronic effects, collectively enabling pronounced bathochromic shifts in absorption without compromising energy storage capacity and duration. Comprehensive electronic structure analyses carried out using the CASSCF, CASPT2, and DLPNO-CCSD(T) methods ensure the robustness of the findings. This study provides valuable design principles for next-generation MOST systems by leveraging the cooperative effects of non-covalent interactions and electronic modulation through functionalization.