In Silico Design of Dihydroazulene/Vinylheptafulvene Photoswitches for Solar-Energy Storage Guided by an All-Around Performance Descriptor**

A major challenge in the development of molecular photoswitches capable of storing and releasing solar energy is to simultaneously realize many of the performance criteria required of the switches for such applications. Here, we take on this challenge by introducing an all-around performance descriptor that combines three key criteria (related to energy density, storage time and light-absorption characteristics), and by using density functional theory methods to calculate its values for 52 newly designed dihydroazulene/vinylheptafulvene (DHA/VHF) switches. Thereby, we are able to identify several switches with excellent overall properties that contain a structural motif absent in all DHA/VHF compounds previously considered for solar-energy storage. For some of these switches, we also provide retrosynthetic analyses and demonstrate that they form the energy-storing VHF isomer through a facile DHA→VHF photoisomerization reaction. All in all, we conclude that these switches show great promise for further development towards applications in solar-energy storage.