Publications by authors named "Mitra Ataelahi"

2 Publications

  • Page 1 of 1

Photophysics and photochemistry of cis- and trans-hydroquinone, catechol and their ammonia clusters: a theoretical study.

Photochem Photobiol Sci 2015 Feb;14(2):457-64

Department of Chemistry, University of Isfahan, 81746-73441 Isfahan, Iran.

Excited state hydrogen transfer in hydroquinone- and catechol-ammonia clusters has been extensively investigated by high level ab initio methods. The potential energy profiles of the title systems at different electronic states have been determined at the MP2/CC2 levels of theory. It has been predicted that double hydrogen transfer (DHT) takes place as the main consequence of photoexcited tetra-ammoniated systems. Consequently, the DHT processes lead the excited systems to the (1)πσ*-S0 conical intersections, which is responsible for the ultrafast non-radiative relaxation of UV-excited clusters to their ground states. Moreover, according to our calculated results, the single hydrogen detachment or hydrogen transfer process essentially governs the relaxation dynamics of smaller sized clustered systems (mono- and di-ammoniated).
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http://dx.doi.org/10.1039/c4pp00356jDOI Listing
February 2015

Microhydration effects on the electronic properties of protonated phenol: a theoretical study.

J Phys Chem A 2013 Dec 21;117(48):12842-50. Epub 2013 Nov 21.

Department of Chemistry, University of Isfahan , 81746-73441 Isfahan, Iran.

The CC2 (second-order approximate coupled cluster method) has been employed to investigate microhydration effect on electronic properties of protonated phenol (PhH(+)) According to the CC2 calculation results on electronic excited states of microhydrated PhH(+), for the S1 and S2 electronic states, which are of (1)ππ* nature and belong to the A' representation of molecular Cs point group, a significant blue shift effect on the S1 and S2 electronic states, which are of 1ππ* nature and belong to the A' representation of molecular Cs point group, in comparison to corresponding transitions on bare cation (PhH(+)), has been predicted. Nevertheless, for the S3-S0 (1A'', 1σπ*) transition, a large red shift effect has been predicted. Furthermore, it has been found that the lowest (1)σπ* state plays a prominent role in the photochemistry of these systems. In the bare protonated phenol, the (1)σπ* state is a bound state with a broad potential curve along the OH stretching coordinate, while it is dissociative in microhydrated species. This indicates to a predissociation of the S1((1)ππ*) state by a low-lying (1)σπ* state, which leads the excited system to a concerted proton-transfer reaction from protonated chromophore to the solvent. The dissociative (1)σπ* state in monohydrated PhH(+) has small barrier, while increasing the solvent molecules up to three removes the barrier and consequently expedites the proton-transfer reaction dynamics.
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http://dx.doi.org/10.1021/jp409537sDOI Listing
December 2013
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