Resolving the turnover of temperature dependence of the reaction rate in barrierless isomerization

Article Abstract:

The temperature dependence of the barrierless cis-trans isomerization reaction in the excited state of 1,1'-diethyl-4,4'-cyanine was investigated. Measurement of transient absorption kinetics and transient absorption spectra at different temperatures and viscosities showed dynamic information on the isomerization process of constant viscosity. Results suggest a crossover of reaction rate from a negative temperature dependence at low viscosities to a positive temperature dependence at higher viscosities. This is due to the competition between the two processes following excitation.

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Dynamics of excited states of the carotenoid peridinin in polar solvents: dependence on excitation wavelength, viscosity, and temperature

Article Abstract:

Several equlibria occur between Fe(super 3+), Fe(super 2+), Cl(super -), the neutral carotenoid, and its radical cation and dication in the oxidation of carotenoids, ethyl all-trans-8'-apo-beta-caroten-8'-oate and all-trans-beta-carotene, with ferric chloride. The radical cation and dication were found to abstract an electron from Fe(super 2+) and in the presence of air, a stable product is formed in high yield.

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Ultrafast formation of trinitromethanide (C(NO2)3(super -)) by photoinduced dissociative electron transfer and subsequent ion pair coupling reaction in acetonitrile and dichloromethane

Article Abstract:

Femtosecond pump-probe spectroscopy was used for studying the tetranitromethane-naphthalene charge-transfer complexes in acetonitrile and dichloromethane, which were excited at 400 nm, and the resultant dynamics were investigated. The efficient ion pair coupling due to the slower solvent separation of the N(super +)T(super -) ion pair could be responsible for the faster overall decay rates in dichloromethane.

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