Esmaspäeval, 11. juunil 2018 kell 14.15 toimub Physicumis, W.Ostwaldi 1 seminariruumis D312
Laserspektroskoopia seminar No 259
Esineb Dr. Veera Krasnenko , TÜ FI laserspektroskoopia labor
The similarity of vibronic mechanisms during dimerization and reverse recovery of the aromatic compounds
The vibronic interactions may play a significant role in the covalent bonds formation and breaking between adjacent aromatic compounds. The recent investigations [1-4] have predicted the possibility of covalent dimerization of benzene molecules (bi-benzene), covalently conjoined structures of benzene molecule and graphene sheet (graphene can consider as an indefinitely large aromatic molecule) indicating on the similar vibronic mechanism of their formation.
The existence of the above-described structures is confirmed by the presence of dimerized thymine bases in deoxyribonucleic acid (DNA), which may lead to skin cancer (see, e.g. [5-7]). Moreover, according to performed research, the most energetically favorable of the predicted structures of bi-benzene, benzene-graphene and thymine-graphene have a very similar shape, like the thymine dimer created by UV light in DNA . The thymine nucleobase is a pyrimidine derivative, which has a six-membered aromatic ring similar to a central structure of the benzene molecule, but with two nitrogen atoms in the ring instead of carbons. The resemblance of the central structural elements in these aromatic molecules allows suggesting that the formation and reverse dissociation of dimers is determined by analogous vibronic mechanisms. Thus, UV radiation of aromatic molecules, physisorbed on graphene, may lead to the appearance of covalent functionalization of graphene basal plane.
The purpose of this work is to apply developed in Refs. [1-3] the vibronic interactions calculation method for investigation of excited states of molecular dimers in DNA and molecules on graphene. In this work, the results of numerical calculations of the potential surface of bi-benzene (with a view to determining a pathway of formation of the thymine dimers in DNA) and the covalently bound structure of thymine molecule and graphene sheet (with a view to promoting the functionalization of graphene) are presented. The Raman spectra to determine how covalently bound structures differ from the initial ones were calculated using DFT (Density Function Theory) method. The calculated spectra are in a good agreement with available experimental data and are significantly different, depending on the presence or absence of covalent bonds between the compounds studied.
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