Ultrafast Hot Exciton Nonadiabatic Excited-State Dynamics in Green Fluorescent Protein Chromophore Analogue

The ultrafast high-energy nonadiabatic excited-state dynamics of benzylidenedimeth-ylimidazolinone (BDI) chromophore dimer has been investigated using an electronic structure method coupled with on-the-fly quantitative wave function analysis to gain an insight into the photophysics of hot excitons in biological systems. The dynamical simulation provides a rationalization of the behavior of exciton in dimer after photoabsorption of light to higher energy states. The results suggest that hot exciton localization within the manifold of excited states is caused by the hindrance of ΦI- and ΦP - torsional rotation in the monomeric units of a dimer. This hindrance arises due to weak π-π stacking interaction in the dimer resulting in an energetically uphill excited-state barrier for ΦI- and ΦP - twisted rotation impeding the isomerization process in chromophore. Thus, the study highlights the potential impact of the weak π-π interaction regulating the photodynamics of the green fluorescent protein chromophore derivatives.