Deactivation mechanism of the green fluorescent chromophore.
We report time-resolved fluorescence data for the anion of p-hydroxybenzylidene dimethylimidazolinone (p-HBDI), a model chromophore of the green fluorescence protein, in viscous glycerol-water mixtures over a range of temperatures, T. The markedly nonexponential decay of the excited electronic state is interpreted with the aid of an inhomogeneous model possessing a Gaussian coordinate-dependent sink term. A nonlinear least-squares fitting routine enables us to achieve quantitative fits by adjusting a single activation parameter, which is found to depend linearly on 1/T. We derive an analytic expression for the absolute quantum yield, which is compared with the integrated steady-state fluorescence spectra. The microscopic origins of the model are discussed in terms of two-dimensional dynamics, coupling the phenyl-ring rotation to a swinging mode that brings this flexible molecule to the proximity of a conical intersection on its multidimensional potential energy surface.
Gepshtein
Rinat
R
Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel.
Huppert
Dan
D
Agmon
Noam
N
D005453:Fluorescence; D005990:Glycerol / Q000737:chemistry; D048288:Imidazolines / Q000737:chemistry* / Q000528:radiation effects; D008027:Light; D008956:Models, Chemical; D015394:Molecular Structure; D013696:Temperature; D014783:Viscosity; D014867:Water / Q000737:chemistry
C502519:4-hydroxybenzylidene-1,2-dimethylimidazolinone; D048288:Imidazolines; D014867:Water; D005990:Glycerol