DFT Study of Carbamoyl-substituted Dihydroazulene / Vinylheptafulvene Derivatives and Solvent Effects

Systematic functionalization of the dihydroazulene (DHA) / vinylheptafulvene (VHF) photo- /thermoswitch allows for tuning of the thermochemical and optical properties of the system, which is of particular relevance for improving its capabilities as a solar energy storage and release system. Using a computational chemistry approach, this work investigates the thermochemical and optical properties of several different DHA/VHF systems bearing on position C1 of DHA amide or ester electron-acceptor groups. Solvent effects were investigated using a polarizable dielectric medium model for the solvents cyclohexane, toluene, dichloromethane, ethanol and acetonitrile along with calculations in vacuum. All systems show increased energy storage density compared to the 1,1- dicyano parent system, with generally lower activation barriers for the VHF-to-DHA back-conversion across all solvents. Increasing solvent polarity led to a calculated redshift of the absorption spectra and an increase in intensities for all systems, with values comparable to the parent reference in vacuo and redshifted by around 15 nm in acetonitrile for some compounds. Experimental kinetics studies for the VHF-to-DHA conversion were performed and compared to the computational findings.