Molecular Dynamics of Excited State Intramolecular Proton Transfer:  2-(2‘-Hydroxyphenyl)-4-methyloxazole in Gas Phase, Solution, and Protein Environments†

2004 ◽  
Vol 108 (21) ◽  
pp. 6616-6623 ◽  
Author(s):  
Oriol Vendrell ◽  
Miquel Moreno ◽  
José M. Lluch ◽  
Sharon Hammes-Schiffer
Keyword(s):  
Molecular Dynamics ◽  
Excited State ◽  
Proton Transfer ◽  
Gas Phase ◽  
Intramolecular Proton Transfer ◽  
Phase Solution

Photorelaxation of imidazole and adenine via electron-driven proton transfer along H2O wires

2016 ◽  
Vol 195 ◽  
pp. 237-251 ◽  
Author(s):  
Rafał Szabla ◽  
Robert W. Góra ◽  
Mikołaj Janicki ◽  
Jiří Šponer
Keyword(s):  
Molecular Dynamics ◽  
Excited State ◽  
Potential Energy ◽  
Proton Transfer ◽  
Potential Energy Surface ◽  
Molecular Dynamics Simulations ◽  
Gas Phase ◽  
Energy Surface ◽  
Water Molecules ◽  
Dynamics Simulations

Photochemically created πσ* states were classified among the most prominent factors determining the ultrafast radiationless deactivation and photostability of many biomolecular building blocks. In the past two decades, the gas phase photochemistry of πσ* excitations was extensively investigated and was attributed to N–H and O–H bond fission processes. However, complete understanding of the complex photorelaxation pathways of πσ* states in the aqueous environment was very challenging, owing to the direct participation of solvent molecules in the excited-state deactivation. Here, we present non-adiabatic molecular dynamics simulations and potential energy surface calculations of the photoexcited imidazole–(H2O)5 cluster using the algebraic diagrammatic construction method to the second-order [ADC(2)]. We show that electron driven proton transfer (EDPT) along a wire of at least two water molecules may lead to the formation of a πσ*/S0 state crossing, similarly to what we suggested for 2-aminooxazole. We expand on our previous findings by direct comparison of the imidazole–(H2O)5 cluster to non-adiabatic molecular dynamics simulations of imidazole in the gas phase, which reveal that the presence of water molecules extends the overall excited-state lifetime of the chromophore. To embed the results in a biological context, we provide calculations of potential energy surface cuts for the analogous photorelaxation mechanism present in adenine, which contains an imidazole ring in its structure.

Theoretical investigation of 2-(iminomethyl)phenol in the gas phase as a prototype of ultrafast excited-state intramolecular proton transfer

2016 ◽  
Vol 657 ◽  
pp. 113-118 ◽  
Author(s):  
Rathawat Daengngern ◽  
Chanatkran Prommin ◽  
Thanyada Rungrotmongkol ◽  
Vinich Promarak ◽  
Peter Wolschann ◽  
...  
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Gas Phase ◽  
Theoretical Investigation ◽  
Intramolecular Proton Transfer

scholarly journals Excited state intramolecular proton transfer in hydroxyanthraquinones: Toward predicting fading of organic red colorants in art

2019 ◽  
Vol 5 (9) ◽  
pp. eaaw5227 ◽  
Author(s):  
J.A. Berenbeim ◽  
S. Boldissar ◽  
S. Owens ◽  
M.R. Haggmark ◽  
G. Gate ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Proton Transfer ◽  
Gas Phase ◽  
Intramolecular Proton Transfer ◽  
Structural Trend ◽  
Works Of Art ◽  
Proton Transfers ◽  
Proposed Model ◽  
High Level

Compositionally similar organic red colorants in the anthraquinone family, whose photodegradation can cause irreversible color and stability changes, have long been used in works of art. Different organic reds, and their multiple chromophores, suffer degradation disparately. Understanding the details of these molecules’ degradation therefore provides a window into their behavior in works of art and may assist the development of improved conservation methods. According to one proposed model of photodegradation dynamics, intramolecular proton transfer provides a kinetically favored decay pathway in some photoexcited chromophores, preventing degradation-promoting electron transfer (ET). To further test this model, we measured excited state lifetimes of substituted gas-phase anthraquinones using high-level theory to explain the experimental results. The data show a general structural trend: Anthraquinones with 1,4-OH substitution are long-lived and prone to damaging ET, while excited state intramolecular proton transfers promote efficient quenching for hydroxyanthraquinones that lack this motif.

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