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Download fileMapping the Triplet Potential Energy Surface of 1-Methyl-8-nitronaphthalene
journal contribution
posted on 2005-07-22, 00:00 authored by Svetlana V. Kombarova, Yuri V. Il'ichevSpin-unrestricted calculations and time-dependent DFT were used to characterize structure and
reactivity of 1-methyl-8-nitronaphthalene (1) in the triplet state. Four hybrid models (B3LYP, PBE0,
MPW1K, BHLYP) with significantly different amount of the exact exchange were employed. The
triplet potential energy surface of 1 was mapped by using the UB3LYP and UMPW1K techniques.
Both hybrid models provided qualitatively consistent pictures for the potential energy landscape.
Thirty-one stationary points, of which 15 were minima, were found at the UB3LYP level of theory.
Three minima corresponding to the nitro form of 1 were located on the triplet surface; just one was
found for the singlet ground state. Two reaction paths leading from 1 either to a nitrite-type
intermediate (2) or to the aci-form (3) were characterized. For both paths, reaction products were
of diradical nature. The lower activation energy was obtained for the triplet-state tautomerization
affording 3. The ground state of triplet multiplicity was predicted for two isomers of the aci-form.
The triplet diradical 3 is expected to react through the thermal population of a close-lying singlet
excited state. The results are discussed in relation to mechanisms of photoinduced rearrangements
of peri-substituted nitronaphthalenes that can be used to develop novel photolabile protecting groups.
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triplet surfacetriplet statenitro formUB 3LYPEnergy Surfaceenergy surfacesinglet ground statephotoinduced rearrangementsPBEaciminimaUB 3LYP levelground stateBHLYPdiradical naturetriplet multiplicityDFTnovel photolabilereaction pathsreaction productsactivation energyenergy landscapemodeltriplet diradical 3UMPW 1K techniques