On the spectral properties of methyl and methoxy derivatives of 1,3-diphenyl-1H-pyrazolo[3,4-b]quinoxalines: Experiment and DFT/TDDFT calculations

P Gasiorski; M Matusiewicz; E Gondek; T Uchacz; K Wojtasik; A Danel; Ya Shchur; A V Kityk

doi:10.1016/j.saa.2017.05.060

On the spectral properties of methyl and methoxy derivatives of 1,3-diphenyl-1H-pyrazolo[3,4-b]quinoxalines: Experiment and DFT/TDDFT calculations

Spectrochim Acta A Mol Biomol Spectrosc. 2017 Nov 5:186:89-98. doi: 10.1016/j.saa.2017.05.060. Epub 2017 Jun 6.

Authors

P Gasiorski¹, M Matusiewicz¹, E Gondek², T Uchacz³, K Wojtasik⁴, A Danel⁴, Ya Shchur⁵, A V Kityk⁶

Affiliations

¹ Faculty of Electrical Engineering, Częstochowa University of Technology, Al. Armii Krajowej 17,42-200 Częstochowa, Poland.
² Institute of Physics, Cracow University of Technology, Podhorążych 1, 30-084 Kraków, Poland.
³ Faculty of Chemistry, Jagiellonian University, Ingardena str. 3, 30-060 Kraków, Poland.
⁴ Faculty of Food Technology, Institute of Chemistry, University of Agriculture, Balicka Str. 122, 30-149 Kraków, Poland.
⁵ Institute for Condensed Matter Physics, 1 Svientsitskii str., 79011 Lviv, Ukraine.
⁶ Faculty of Electrical Engineering, Częstochowa University of Technology, Al. Armii Krajowej 17,42-200 Częstochowa, Poland. Electronic address: kityk@ap.univie.ac.at.

PMID: 28623840
DOI: 10.1016/j.saa.2017.05.060

Abstract

Paper reports the synthesis and spectroscopic studies of two novel 1,3-diphenyl pyrazoloquinoxaline (PQX) derivatives with 6-substituted methyl (MePQX) or methoxy (MeOPQX) side groups. The optical absorption and fluorescence emission spectra are recorded in solvents of different polarity. Other photophysical constants, such as the fluorescence lifetime and quantum yield, radiationless and radiative rate constants, electronic transition dipole moments, give complete characterization of MePQX and MeOPQX dyes as materials for potential luminescence or electroluminescence applications. Measured optical absorption and fluorescence emission spectra are compared with the results of quantum-chemical analysis using density functional theory (DFT/TDDFT) methods based on hybrid and long range corrected (LRC) exchange-correlation (xc) functionals in combination with solvation self consistent reaction field model. Comparing to conventional hybrid xc-functionals, the DFT/TDDFT calculations using LRC xc-functionals yield considerably more accurate description of optical absorption and fluorescence emission spectra. The best description of the absorption-emission circle provides the model assuming that optical absorption takes place from preferably flat or weakly twisted molecular conformations in the ground state, as particularly is suggested by the geometrical DFT optimization, whereas the fluorescence emission would be expected from more twisted molecular conformations in the excited state.

Keywords: DFT/TDDFT calculations; Fluorescence spectra; Optical absorption spectra; Pyrazoloquinoxaline derivatives.