The Amorphism of the Polycrystal Phase Transition in the Course Of Cis-Trans Photoisomerization
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Abstract:
Abstract This work is devoted to the study of cis-trans photoisomerization of 1,2-di(1-naphtyl)-ethylene (DNE) in the condensed phase. The reaction of photoisomerization of the diaryl-ethylene is well known,1 the reaction of cis-trans photoisomerization occurring even at 77°K. This reaction is believed to occur with a decrease of the molecular volume.2 Therefore, we supposed that the reaction of cis-trans isomerization would occur in the condensed solid state.Keywords:
Cis–trans isomerism
Diradical
Conical intersection
Azulene
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Photoisomerization and thermal isomerization behaviors of an extensive series of arylazoimidazoles are investigated. Absorption spectra are characterized by a structured ππ* absorption band around 330−400 nm with a tail on the lower energy side extending to 500 nm corresponding to an nπ* transition. The trans-to-cis photoisomerization occurs on excitation into these absorption bands. The quantum yields are dependent on the excitation wavelength, as observed for azobenzene derivatives, but are generally larger than those of azobenzene. The thermal cis-to-trans isomerization rates are also generally larger than that of azobenzene and are comparable to those of 4-N,N-dimethylaminoazobenzene and 4-nitroazobenzene. Arylazoimidazoles with no substituent on the imidazole nitrogen are unique in that the quantum yield for the trans-to-cis photoisomerization and the rate of thermal cis-to-trans isomerization are particularly large. It is proposed that the fast thermal isomerization is due to an involvement of self-catalyzed and protic molecule-assisted tautomerization to a hydrazone form.
Azobenzene
Quantum yield
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Photostationary state
Quantum yield
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Photostationary state
Radical ion
Cis–trans isomerism
Flash photolysis
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CIDNP
Cis–trans isomerism
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Electron acceptor
Methylene
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Journal of the Chemical Society Faraday Transactions 1 Physical Chemistry in Condensed Phases (1972)
Additional results on the effect of additives on the product yields in the vapour-phase photolysis of trans-but-2-ene and cis-pent-2-ene are reported. They confirm, extend and reconcile our previous results with those of Chesick. The main photoreaction could be quenched by all additives at both wavelengths; at 203 nm, and with some additives at 185 nm, quenching was accompanied by photoisomerization. The effects can be correlated with the two states, Rydberg and V(π→π*), which are excited at the two wavelengths. Collisional deactivation of the V state results in photoisomerization while when the R state is deactivated no isomerization occurs. Apparently there is no ready collisional interconversion of the R and V states.
Ene reaction
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Cis–trans isomerism
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