Theoretical assessment of indolylfulgimides and novel asymmetric di-indolylfulgimide photochromes

Density Functional Theory (DFT) and Time Dependent-Density Functional Theory (TD-DFT) were used to simulate the electronic and absorbance properties of mono- and di-fulgimide based photochromes. TD-M06//M06 effectively simulated 22 known indolylfulgimides, and the observed absorbance maxima were calculated within ±0.08 eV (±15 nm). Accurate simulation of 3 bisfulgimides (±0.09 eV, ±11 nm) further validated the method for assessing larger molecules with multiple photochromes. Seven novel indolylfulgimides were simulated and used in the design, simulation and analysis of 6 theoretical asymmetric di-indolylfulgimides. The di-indolylfulgimide D4 showed the greatest potential as an all-photonic multi-addressable photochrome. The data highlight the effectiveness of TD-DFT//DFT for simulating photochromic molecules and provide insight into the challenges involved in designing novel multi-photochromic systems.