Tuned CAM-B3LYP functional in the time-dependent density functional theory scheme for excitation energies and properties of diarylethene derivatives

We present the CAM (Coulomb Attenuated Method)-B3LYP functional tuned for excitation energies and properties of diarylethene derivatives in the time-dependent density functional theory (TD-DFT) scheme. The CAM-B3LYP parameters are tuned so as to well reproduce the experimental excitation energies and properties of a prototypical diarylethene derivative. The TD-DFT method with the tuned CAM-B3LYP parameters (μ = 0.150, α = 0.0799 and β = 0.9201) is found to semi-quantitatively reproduce several excitation energies obtained from the experimental UV–vis spectra of 15 closed forms of diarylethene derivatives. In contrast, it turns out that the use of default CAM-B3LYP parameters (μ = 0.33, α = 0.19, and β = 0.46) fails to well reproduce these experimental UV–vis spectra. We also clarified that this difference does not originate from the functional dependence of the ground state optimized geometry, but from the CAM-B3LYP parameter dependences of excitation energies and properties in the TD-DFT scheme.