Tunneling in spin-state interconversion of ferrous spin-crossover complexes. Concentration dependence of apparent activation energy determined in solution by laser-flash photolysis

1989 ◽  
Vol 111 (4) ◽  
pp. 1171-1180 ◽  
Author(s):  
Andrew J. Conti ◽  
Chuan Liang Xie ◽  
David N. Hendrickson
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Concentration Dependence ◽  
Spin State ◽  
Spin Crossover ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Spin Crossover Complexes

The insertion of germylene into the H—H bond; rate constant limits and thermochemistry. Ab initio and DFT calculations on the reactions of GeH2 and SiH2 with H2

2000 ◽  
Vol 78 (11) ◽  
pp. 1428-1433 ◽  
Author(s):  
Rosa Becerra ◽  
Sergey E Boganov ◽  
Mikhail P Egorov ◽  
Valery I Faustov ◽  
Oleg M Nefedov ◽  
...  
Keyword(s):  
Activation Energy ◽  
Ab Initio ◽  
Potential Energy Surfaces ◽  
Elevated Temperatures ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Activation Parameters ◽  
Laser Flash ◽  
Bimolecular Reaction ◽  
Energy Surfaces

The technique of laser flash photolysis in the gas-phase has been used to set limits on the rate constants for the bimolecular reaction of germylene (GeH2) with deuterium (D2) at both ambient and elevated temperatures (585 K). These limits show that the activation energy for the insertion of GeH2 into the H—H bond is at least 19 (±6) kJ mol–1. Thermochemical arguments place the activation energy approximately in the range 63–84 kJ mol–1. DFT B3LYP/6-311++G(3df,2pd) and ab initio QCISD(T)/6-311G++(3df,2pd)//QCISD/6-311G(d,p) calculations have been carried out on the potential energy surfaces of reactions ZH2 + H2 [Formula: see text] ZH4 (Z= Ge, Si). Both methods predict the same mechanisms for germylene and silylene insertion which include formation of loose prereaction complexes and transition states of similar structure. The prereaction complex is only about half as strong in the case of germylene (ΔH (298 K) = –9 (–11) kJ mol–1) as in the case of silylene (ΔH (298 K) = –16 (–21) kJ mol–1) (QCISD values cited with B3LYP values in parentheses). The differences in activation energies are even more significant. Germylene insertion has a very high barrier of 58 (56) kJ mol–1 compared to that of silylene 13 (6) kJ mol–1. Calculated activation parameters for both reactions are in reasonable consistency with experimental results. Reasons for the enhanced H—H insertion barrier for germylene compared with silylene are discussed.Key words: laser flash photolysis, germylene, silylene, deuterium, activation energy, thermochemistry, ab initio calculation, DFT B3LYP calculation.

Effect of Aggregation on Bacteriochlorin a Triplet-state Formation: A Laser Flash Photolysis Study¶

2002 ◽  
Vol 76 (5) ◽  
pp. 480 ◽  
Author(s):  
Xavier Damoiseau ◽  
Francis Tfibel ◽  
Maryse Hoebeke ◽  
Marie-Pierre Fontaine-Aupart
Keyword(s):  
Triplet State ◽  
State Formation ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash

A Laser Flash Photolysis and Pulse Radiolysis Study of Primary Photochemical Processes of Flumequine¶

2000 ◽  
Vol 72 (4) ◽  
pp. 451 ◽  
Author(s):  
M. Bazin ◽  
F. Bosca ◽  
M. L. Marin ◽  
M. A. Miranda ◽  
L. K. Patterson ◽  
...  
Keyword(s):  
Pulse Radiolysis ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Photochemical Processes

Laser Flash Photolysis Studies of the UVA Sunscreen Mexoryl® SX

1999 ◽  
Vol 70 (3) ◽  
pp. 292
Author(s):  
Ann Cantrell ◽  
David J. McGarvey ◽  
Louise Mulroy ◽  
T. George Truscott
Keyword(s):  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash

Singlet Methylene Removal Rate Constants from the (0,1,0) Vibrational Level: Enhancement via Complex-Mediated Vibrational Relaxation

2001 ◽  
Vol 215 (6) ◽  
Author(s):  
M.A. Buntine ◽  
G.J. Gutsche ◽  
W.S. Staker ◽  
M.W. Heaven ◽  
K.D. King ◽  
...  
Keyword(s):  
Vibrational Level ◽  
Rate Constants ◽  
Vibrational Relaxation ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Removal Rate ◽  
Laser Flash ◽  
Laser Absorption ◽  
Photolysis Laser ◽  
Singlet Methylene

The technique of laser flash photolysis/laser absorption has been used to obtain absolute removal rate constants for singlet methylene,

Electron transfer sensitized photolysis of 'onium salts

1988 ◽  
Vol 66 (2) ◽  
pp. 319-324 ◽  
Author(s):  
R. J. DeVoe ◽  
M. R. V. Sahyun ◽  
Einhard Schmidt ◽  
N. Serpone ◽  
D. K. Sharma
Keyword(s):  
Electron Transfer ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Quantitative Model ◽  
Intersystem Crossing ◽  
Single Electron Transfer ◽  
Onium Salts ◽  
Encounter Complex ◽  
Back Electron Transfer

We have studied the anthracene-sensitized photolyses of both diphenyliodonium and triphenylsulphonium salts in solution using both steady-state and laser flash photolysis techniques. Photoproducts, namely, phenylated anthracenes along with iodobenzene or diphenylsulphide, respectively, are obtained from both salts with quantum efficiencies of ca. 0.1 at 375 nm. We infer the intermediacy of diphenyliodo and triphenylsulphur radicals formed by single electron transfer from the singlet-excited anthracene. We have developed a quantitative model of this chemistry, and identify the principal sources of inefficiency as back electron transfer, which occurs at nearly the theoretically limiting rate, intersystem crossing from the initially formed sensitizer–'onium salt encounter complex, and in-cage radical recombination.

Phototransformations of bridgehead-substituted dibenzobarrelenes. Steady-state and laser flash photolysis studies

1987 ◽  
Vol 52 (25) ◽  
pp. 5512-5517 ◽  
Author(s):  
S. Pratapan ◽  
K. Ashok ◽  
D. R. Cyr ◽  
P. K. Das ◽  
M. V. George
Keyword(s):  
Steady State ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash
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