Ab Initio Investigation of Proton Transfer in Ammonia−Hydrogen Chloride and the Effect of Water Molecules in the Gas Phase

1998 ◽  
Vol 102 (26) ◽  
pp. 5117-5123 ◽  
Author(s):  
Robert A. Cazar ◽  
Alan J. Jamka ◽  
Fu-Ming Tao
Keyword(s):  
Proton Transfer ◽  
Ab Initio ◽  
Gas Phase ◽  
Hydrogen Chloride ◽  
Water Molecules ◽  
Effect Of Water

Ab Initio Study of Gas-Phase Proton Transfer in Ammonia−Hydrogen Halides and the Influence of Water Molecules

1999 ◽  
Vol 103 (38) ◽  
pp. 7719-7724 ◽  
Author(s):  
James A. Snyder ◽  
Robert A. Cazar ◽  
Alan J. Jamka ◽  
Fu-Ming Tao
Keyword(s):  
Proton Transfer ◽  
Ab Initio ◽  
Gas Phase ◽  
Water Molecules ◽  
Ab Initio Study ◽  
Hydrogen Halides ◽  
Influence Of Water

Identity-reaction proton transfers from oxygen acids yielding localized vs. delocalized conjugate bases. An ab initio study

1999 ◽  
Vol 77 (5-6) ◽  
pp. 810-816 ◽  
Author(s):  
James E Van Verth ◽  
William H Saunders, Jr.
Keyword(s):  
Proton Transfer ◽  
Ab Initio ◽  
Gas Phase ◽  
Heavy Atom ◽  
Proton Donor ◽  
Proton Transfers ◽  
Straight Line ◽  
Large Positive Deviation ◽  
Experimental Values ◽  
Conjugate Bases

Identity-reaction proton transfers from a series of oxygen acids to the corresponding conjugate bases have been studied by ab initio methods at the MP2/6-31+G*//MP2/6-31+G* level. The acids are H3O+, CH3OH2+, CH2 = OH+, HC(O)OH2+, CH2 = CHOH2+, H2O, CH3OH, HOOH, HOCH2OH, FOH, FCH2OH, HC(O)OH, and CH2 = CHOH. Gas-phase acidities were calculated at the G2(MP2) level in order to have benchmark values for all acidities regardless of whether experimental values were available. Barriers to proton transfer relative to the separated reactants, ΔHTS, show a straight-line relation to acidity for all but two of the neutral acids and for all but one of the cationic acids. Two neutral acids, HOOH and FOH, show negative deviations that can be attributed to polarizability of the atoms attached to the proton donor oxygens. The cationic acid HC(O)OH2+ shows a large positive deviation, which probably arises from substantial heavy-atom reorganization from reactant to TS. Charges provide evidence of a lag in delocalization in the reaction of CH2 = CHOH2+, though it does not show an elevated ΔHTS.Key words: ab initio, oxygen acids, proton transfer, acidity.

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.

The Effect of Water on Proton Transfer in Pyrazole

1977 ◽  
Vol 32 (11-12) ◽  
pp. 891-893 ◽  
Author(s):  
V. N. Babin ◽  
E. B. Zavelovich ◽  
Yu. A. Belousov
Keyword(s):  
Transition Metal ◽  
Proton Transfer ◽  
Metal Ions ◽  
Transition Metal Ions ◽  
Water Molecules ◽  
Effect Of Water ◽  
Rearrangement Effect

Abstract An NMR 13C study has shown that proton rearrangement in pyrazole is decreased by adding small amounts of water to the sample. Single water molecules as coordination centres pertrub the mechanism of cooperative proton transfer occurring in pyrazole selfassociates. The decrease of the rearrangement effect due to water is similar to the action of transition metal ions studied by the authors earlier.

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