Tuning the UV spectrum of PAHs by means of different N-doping types taking pyrene as paradigmatic example: categorizationviavalence bond theory and high-level computational approaches

0533461 - ÚOCHB 2021 RIV GB eng J - Journal Article
Shao, X. - Aquino, A. J. A. - Otyepka, M. - Nachtigallová, Dana - Lischka, H.
Tuning the UV spectrum of PAHs by means of different N-doping types taking pyrene as paradigmatic example: categorizationviavalence bond theory and high-level computational approaches.
Physical Chemistry Chemical Physics. Roč. 22, č. 38 (2020), s. 22003-22015. ISSN 1463-9076. E-ISSN 1463-9084
R&D Projects: GA ČR(CZ) GA18-09914S
Institutional support: RVO:61388963
Keywords : nitrogen-doped graphene * state perturbation theory * quantum dots
OECD category: Physical chemistry
Impact factor: 3.676, year: 2020
Method of publishing: Limited access
https://doi.org/10.1039/D0CP02688C

Tuning of the electronic spectra of carbon dots by means of inserting heteroatoms into the pi-conjugated polycyclic aromatic hydrocarbon (PAH) system is a popular tool to achieve a broad range of absorption and emission frequencies. Especially nitrogen atoms have been used successfully for that purpose. Despite the significant progress achieved with these procedures, the prediction of specific shifts in the UV-vis spectra and the understanding of the electronic transitions is still a challenging task. In this work, high-level quantum chemical methods based on multireference (MR) and single-reference (SR) methods have been used to predict the effect of different nitrogen doping patterns inserted into the prototypical PAH pyrene on its absorption spectrum. Furthermore, a simple classification scheme based on valence bond (VB) theory and the Clar sextet rule in combination with the harmonic oscillator measure of aromaticity (HOMA) index was applied to arrange the different doping structures into groups and rationalize their electronic properties. The results show a wide variety of mostly redshifts in the spectra as compared to the pristine pyrene case. The most interesting doping structures with the largest red shifts leading to absorption energies below one eV could be readily explained by the occurrence of diradical VB structures in combination with Clar sextets. Moreover, analysis of the electronic transitions computed with MR methods showed that several of the low-lying excited states possess double-excitation character, which cannot be realized by the popular SR methods and, thus, are simply absent in the calculated spectra.
Permanent Link: http://hdl.handle.net/11104/0311847