Modelling fluorescence lifetimes with TD-DFT: a case study with syn-bimanes

Abstract

Syn-bimanes are a class of fluorophores that are widely used for labelling thiol containing biological systems. We used time-dependent density functional theory (TD-DFT) with various hybrid exchange–correlation functionals (B3LYP, PBE0, M06, BMK, CAM-B3LYP, and M06-2X) within the adiabatic approximation to study various photophysical properties of syn-bimanes, such as the absorption and emission to and from the lowest optically bright state, solvatochromism, and fluorescence lifetimes. The mean unsigned errors (MUEs) for absorption with the hybrid functionals B3LYP, PBE0, and M06, were found to be around 0.1 eV, while errors for BMK and CAM-B3LYP were higher than 0.2 eV. With the exception of B3LYP, the MUEs for emission calculated using other functionals were less than 0.2 eV. PBE0 and M06 were found to yield the most accurate fluorescence lifetime results among the tested functionals, with MUEs under 2.0 ns.