Computer‐Aided Design of Fluorinated Flavin Derivatives by Modulation of Intersystem Crossing and Fluorescence

Abstract

AbstractThis study aims at finding fluorinated flavin derivatives with modified intersystem crossing (ISC) and fluorescence properties. In total, photophysical properties of 8 derivatives were investigated computationally using combined density functional theory and multireference configuration interaction methods. On top of a screening procedure, the excited‐state decay mechanisms of selected chromophores were investigated in detail. Kinetic schemes including fluorescence, ISC as well as internal conversion (IC) channels were set up to unravel the complex excited‐state decay kinetics. We find two chromophores that exhibit promising properties with respect to fluorescence microscopy. Distinctive stabilization of the brightππ* state results in absorption in the green wavelength region and emission of (infra‐)red light. The1(πHπL)⤳3(πH–1πL) ISC channel of the flavin chromophore was found to be deactivated upon both modifications, but nonradiative deactivation of the fluorescence by IC appears to be a problem. Alternative modifications of the pteridine dione moiety were found to result in a marked stabilization ofnπ* states along with activation of El‐Sayed allowed ISC channels. For the latter two compounds, we predict fluorescence to be quenched by ISC followed by efficient population of the long‐livedstate via IC.