Photophysical properties of methyl ketone based multi-responsive electrochromic materials: A theoretical investigation

•Working mechanism of a series of multi-responsive molecular switches.•Density functional theory (DFT) and its time dependent formulation (TDDFT)•The keto-enol tautomerization in solvent with base- assisted process.•Concerted proton coupled electron transfer process (PCET) as working mechanism. The working mechanism of a series of multi-responsive molecular switches has been investigated at atomistic level by using density functional theory (DFT) and its time dependent formulation (TDDFT). The keto-enol tautomerization has been explored considering the base assisted process, which can easily occur with a low activation energy, and also evaluating the feasibility of the electrically generation of the colored enolate form proposed in literature. Our data show that the electrically induced mechanism, consisting of a reduction followed by a proton transfer, is thermodynamically unfavorable, while a concerted proton coupled electron transfer process (PCET) can be proposed as working mechanism, resulting exergonic and able to better combine theoretical and experimental evidences.