TY - JOUR
T1 - Ultrafast excited state relaxation of a model green fluorescent protein chromophore
T2 - Femtosecond fluorescence and transient absorption study
AU - Rajbongshi, Basanta Kumar
AU - Rafiq, Shahnawaz
AU - Bhowmik, Suman
AU - Sen, Pratik
N1 - Publisher Copyright:
© 2022 Elsevier B.V.
PY - 2023/3/5
Y1 - 2023/3/5
N2 - The intrinsic excited state properties of green fluorescent protein (GFP) chromophore have inspired syntheses of its structural analogues with a motivation to replicate or improve its excited state properties for biological imaging. In this work, we report torsional-motion mediated multi-coordinate relaxation pathway to explain the excited state dynamics of a GFP chromophore analogue, (4Z)-4-(4-N,N-Dimethylaminobenzylidene)-1,2-diphenyl-1,4-dihydro-5H-imidazolin-5-one (DPI), using femtosecond fluorescence up-conversion, femtosecond transient absorption and quantum chemical calculations. The excited state dynamics of this chromophore involves the formation of an N,N-disubstituted amine twisting mediated intramolecular charge transfer state on a sub-picosecond timescale. This intramolecular charge transfer event prepares an intermediate state that undergoes a “non-volume conserving” twist motion along an exocyclic double bond. The quantum chemical computations further predict that the twist motion along the exocyclic double bond is activated and leads to the formation of a conical intersection between S1 and S0 states of DPI, which is the main nonradiative channel of deactivation. This study confirms that for a structural analogue of GFP chromophore to exhibit excited state properties like the GFP, would require preventing such nonradiative pathways, which can be achieved by restricting the twisting degree of freedom about the exocyclic double bond.
AB - The intrinsic excited state properties of green fluorescent protein (GFP) chromophore have inspired syntheses of its structural analogues with a motivation to replicate or improve its excited state properties for biological imaging. In this work, we report torsional-motion mediated multi-coordinate relaxation pathway to explain the excited state dynamics of a GFP chromophore analogue, (4Z)-4-(4-N,N-Dimethylaminobenzylidene)-1,2-diphenyl-1,4-dihydro-5H-imidazolin-5-one (DPI), using femtosecond fluorescence up-conversion, femtosecond transient absorption and quantum chemical calculations. The excited state dynamics of this chromophore involves the formation of an N,N-disubstituted amine twisting mediated intramolecular charge transfer state on a sub-picosecond timescale. This intramolecular charge transfer event prepares an intermediate state that undergoes a “non-volume conserving” twist motion along an exocyclic double bond. The quantum chemical computations further predict that the twist motion along the exocyclic double bond is activated and leads to the formation of a conical intersection between S1 and S0 states of DPI, which is the main nonradiative channel of deactivation. This study confirms that for a structural analogue of GFP chromophore to exhibit excited state properties like the GFP, would require preventing such nonradiative pathways, which can be achieved by restricting the twisting degree of freedom about the exocyclic double bond.
KW - Charge transfer
KW - Excited state dynamics
KW - Femtosecond spectroscopy
KW - GFP chromophore
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U2 - 10.1016/j.molstruc.2022.134538
DO - 10.1016/j.molstruc.2022.134538
M3 - Article
AN - SCOPUS:85145770935
SN - 0022-2860
VL - 1275
JO - Journal of Molecular Structure
JF - Journal of Molecular Structure
M1 - 134538
ER -