A theoretical study of adiabatic proton transfer to simple substituted allenes in their ground and excited states

1989 ◽  
Vol 67 (12) ◽  
pp. 2188-2195 ◽  
Author(s):  
Peter S. Martin ◽  
Keith Yates ◽  
Imre G. Csizmadia
Keyword(s):  
Proton Transfer ◽  
Experimental Evidence ◽  
Excited States ◽  
Ground State ◽  
Electronic Structures ◽  
Theoretical Study ◽  
Graphical Representation ◽  
Proton Affinities ◽  
Critical Comparison ◽  
Theoretical Predictions

RHF-SCF 3-21G calculations are reported for the 1A′, 1,3A″, 12A′, and 1,32A″ states of simple substituted allenes YCHCCH2, where Y = CH3, H, F, Cl, CF3, and the 1A′ and 1,3A″ states of their Markovnikov (M) and anti-Markovnikov (aM) cations, CHYCHCH2+ and CHYCCH3+, respectively. Equilibrium electronic structures and the mechanism of adiabatic protonation are described qualitatively in terms of Lewis/resonance schematic representations. Calculated proton affinities (PA) suggest that relative to the ground state (1A′), the excited states 1,32A″ are of greatly enhanced basicity with respect to protonation at either regiocenter. A graphical representation of PA(M) versus PA(aM) leads to the following conclusions: (1) irrespective of both regiocenter (M/aM) and state (1A′/32A″/12A″), the PA's for YCHCCH2 decrease with respect to Y in the order CH3 > H > Cl > CF3; (2) the F-substituent gives a PA value greater than that for H- in the ground state, but less than that for H- in the two excited states; (3) for all substituents Y, including CF3, protonation of both 1A′ and 12A″ is predicted to be regioselective in the M direction; (4) regardless of Y, 32A″ exhibits no significant protonation regioselectivity. Critical comparison of these theoretical predictions is made with available experimental evidence. Keywords: proton transfer, excited states, photohydration, allenes.

A theoretical study of adiabatic proton transfer to simple substituted acetylenes In Their Ground And Excited States

1989 ◽  
Vol 67 (12) ◽  
pp. 2178-2187 ◽  
Author(s):  
Peter S. Martin ◽  
Keith Yates ◽  
Imre G. Csizmadia
Keyword(s):  
Experimental Data ◽  
Proton Transfer ◽  
Excited States ◽  
Graphical Representation ◽  
Proton Affinities ◽  
Energy Profiles ◽  
Singlet States ◽  
Vinyl Cation ◽  
Substituted Acetylenes ◽  
Ordered Pairs

RHF SCF 3-21G calculations are reported for the 1Σg+, 1A1, 3A′, and 1,3A″ states of simple substituted acetylenes (Y—C≡C—H, where Y = H, F, Cl,CH3, andCF3), the 1A1, 1A′, and 1.3A″ states of their Markovnikov (M) vinyl cations (Y—C+ = CH2), the 1A′ and 1.3A″ states of their anti-Markovnikov (aM) vinyl cations (YCH=C+H), and the corresponding hydrated vinyl cations. Equilibrium electronic structures and the mechanism of adiabatic protonation are described qualitatively via Lewis/resonance schematic representations of the species involved. Calculated proton affinities (PA) suggest that relative to ground state Y—C≡C—H (1Σ+/1A1), Y—C≡C—H* (1.3A″) is of greatly enhanced basicity with respect to protonation of both regiocenters. A graphical representation of the ordered pairs PA(M) versus PA(aM) as a function of substituent Y and electronic state, leads to the conclusions: (1) irrespective of both regiocenter (M/aM) and state (1Σ1+/1A1, 3A, 1.3A″) the PA's for Y—C≡C—H decrease in the order CH3 > H > Cl> F > CF3; (2) in proceeding from CH3C≡CH to CF3C≡CH, a change in protonation regiospecificity (M → aM) is experienced to approximately the same extent for both S0 and S1; (3) T2 exhibits no significant protonation regioselectivity. Critical comparison of the calculated results is made with available experimental data. An approximate picture of the energy profiles for the adiabatic hydrations of Y—C≡C—H via its ground, triplet and singlet states has been developed, based on the fixed points acetylene, vinyl cation and hydrated vinyl cation. Predicted relative reactivities of these three states are in excellent accord with available experimental data on rates of hydration. Keywords: excited states, proton transfer, photohydration.

scholarly journals Терагерцовая спектроскопия магнитоэлектрика HoAl-=SUB=-3-=/SUB=-(BO-=SUB=-3-=/SUB=-)-=SUB=-4-=/SUB=-

2022 ◽  
Vol 130 (1) ◽  
pp. 59
Author(s):  
А.М. Кузьменко ◽  
В.Ю. Иванов ◽  
А.Ю. Тихановский ◽  
А.Г. Пименов ◽  
А.М. Шуваев ◽  
...  
Keyword(s):  
Crystal Field ◽  
Excited States ◽  
Ground State ◽  
Theoretical Study ◽  
Low Frequency ◽  
Local Symmetry ◽  
Matrix Elements ◽  
The Matrix ◽  
Excitation Conditions ◽  
Ground Multiplet

Experimental and theoretical study of submillimeter (terahertz) spectroscopic and magnetic properties of the rare-earth aluminum borate HoAl3(BO3)4 were performed at temperatures 3–300 K. In the transmittance spectra a number of resonance lines were detected at frequencies 2–35 cm–1 for different radiation polarizations. These modes were identified as transitions between the lower levels of the ground multiplet of the Ho3+ ion split by the crystal field, including both transitions from the ground state to the excited ones and transitions between the excited states. The established excitation conditions of the observed modes and the simulation of the spectra made it possible to separate the magnetic and electric dipole transitions and to determine the energies of the corresponding states, their symmetry, and the matrix elements of the transitions. Low-frequency lines that do not fit into the established picture of the electron states of Ho3+ were also found; these lines, apparently, correspond to the ions with the distorted by defects local symmetry of the crystal field.

Theoretical Study of the Dissociation and Isomerization of NCS

2003 ◽  
Vol 217 (3) ◽  
pp. 255-264 ◽  
Author(s):  
M. Diehr ◽  
G. Chambaud ◽  
H.-J. Werner
Keyword(s):  
Excited States ◽  
Dissociation Energy ◽  
Ground State ◽  
Spectroscopic Data ◽  
Large Scale ◽  
Theoretical Study ◽  
Ground States ◽  
Electronic Ground State ◽  
Barrier Heights ◽  
Electronic Ground

AbstractLarge scale MRCI calculations have been performed to study the electronic ground state and low-lying excited states of the NCS molecule and its isomers. The isomer CNS is found to be stable and linear. It lies 1.29 eV higher in energy than NCS, while CSN has a much higher energy and is unstable. The dissociation energy of the NCS isomer has been calculated to be 4.25 eV. The isomerization paths between the 2Π ground states of both isomers have been mapped by CASSCF and MRCI calculations. The barriers for the NCS → CNS isomerization in 2A′ and 2A″ symmetry have cyclic forms and the barrier heights have been calculated to be 2.71 eV and 2.44 eV, respectively (MRCI). For both isomers, the collinear dissociation paths to the (diatomic + atom) fragments have been investigated by CASSCF calculations. Spectroscopic data are given for the X2Π ground state and for the A2Σ+ state of CNS. The results are compared with the valence isoelectronic system NCO.

A theoretical study on electronic structures and spectroscopic properties of cyclopropane in ground and excited states

2002 ◽  
Vol 279 (1) ◽  
pp. 7-14 ◽  
Author(s):  
Xiaojing Wang ◽  
Seiichi Takami ◽  
Momoji Kubo ◽  
Akira Miyamoto
Keyword(s):  
Excited States ◽  
Electronic Structures ◽  
Theoretical Study ◽  
Spectroscopic Properties

A theoretical study of adiabatic proton transfer to allene in its ground and excited states

1988 ◽  
Vol 170 ◽  
pp. 107-119 ◽  
Author(s):  
Peter S. Martin ◽  
Keith Yates ◽  
Imre G. Csizmadia
Keyword(s):  
Proton Transfer ◽  
Excited States ◽  
Theoretical Study

Theoretical Study of Density Function Theory on Excited States of Methyl Methacrylate

2011 ◽  
Vol 233-235 ◽  
pp. 2871-2874
Author(s):  
Zhi Xong Huang ◽  
Gang Qin ◽  
Ming Zhang ◽  
Yan Qin ◽  
Lian Meng Zhang
Keyword(s):  
Excited State ◽  
Methyl Methacrylate ◽  
Excitation Energy ◽  
Excited States ◽  
Ground State ◽  
Theoretical Study ◽  
Function Theory ◽  
Density Function Theory ◽  
Molecular Structures ◽  
Homo And Lumo

The excited states of methyl methacrylate(MMA) were calculated by CIS method, MMA molecules on the ground and excited states of molecular structures were optimized. The HOMO and LUMO molecular orbitals of MMA molecule are given in the ground state and excited state . The results show that: MMA is excited, the molecular orbital from 27 → 28, the excitation energy is 1.4310eV, Carbon-carbon（C=C）double bonds break.

Excited-state deactivation mechanisms of protonated and neutral phenylalanine: a theoretical study

RSC Advances ◽  
2015 ◽  
Vol 5 (37) ◽  
pp. 29032-29039
Author(s):  
Reza Omidyan ◽  
Mitra Ataelahi ◽  
Gholamhassan Azimi
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Excited States ◽  
Theoretical Study ◽  
Minimum Energy ◽  
Bond Stretching ◽  
Minimum Energy Paths ◽  
Electronic Ground

Minimum energy paths (MEPs) of protonated phenylalanine (PheH+) at the electronic ground and S1 (1ππ*) excited states along the Cα–Cβ bond stretching coordinate, following proton transfer to the aromatic chromophore.

Theoretical Study on the Size Dependence of Ground-State Proton Transfer in 1-Naphthol–Ammonia Clusters

2016 ◽  
Vol 120 (36) ◽  
pp. 7167-7174 ◽  
Author(s):  
Toshihiko Shimizu ◽  
Mitsuhiko Miyazaki ◽  
Masaaki Fujii
Keyword(s):  
Proton Transfer ◽  
Ground State ◽  
Size Dependence ◽  
Theoretical Study ◽  
Ammonia Clusters
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