Influence of catecholic ring torsion on hydroxyflavones

Vladimír Lukeš,Martin Michalík,Monika Biela,Denisa Cagardová

doi:10.2478/acs-2020-0008

Vladimír Lukeš, Martin Michalík + Show 2 more

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https://doi.org/10.2478/acs-2020-0008

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Abstract

Abstract Systematic quantum chemical investigation of quercetin and selected eight mono- and bihydroxyflavonols is presented. Structural analysis based on the Density Functional Theory showed that the energetically preferred conformation of flavonols substituted at the C5 and C3 atoms by a hydroxyl group is stabilised via intramolecular hydrogen bonds occurring between the (C4)O···HO(3 or 5) atomic pairs. Depending on the hydroxyl group positions, energetically preferred torsional orientation of the phenyl ring with respect to the planar benzo-γ-pyrone moiety changed from 0 to 180 degrees. Gas-phase electron transitions were investigated using the time-dependent DFT treatment. The dependence of maximal wavelengths on the torsional deformation of the phenyl ring is of a similar shape, i.e. minima observed for the perpendicular orientation and maxima for the planar one. Shape and energies of the Highest Occupied (HOMO) and Lowest Unoccupied (LUMO) Molecular Orbitals were compared. The obtained theoretical results were compared with available experimental data.

Highlights

Polyphenols are aromatic compounds with large systems of p-electron configurations. Thanks to this configuration they absorb visible light which makes them colourful. Their name derives from the Ancient Greek word poluz and the word phenol which refers to a chemical structure formed by attaching of a hydroxyl (—OH) group to an aromatic benzenoid ring as it is found in alcohols
The more com puting-demanding ab initio methods, e.g. complete active space self-consistent field (CASSCF) method (Andresson and Roos, 1995) or multi-reference configuration interaction (MRCI, Sherrill et al, 1999), are usually successful, but the quality of the obtained results is highly dependent on the selec
Only 180 ° torsion starting with the most stable conformations was considered in the following discussion

Summary

Introduction

Thanks to this configuration they absorb visible light which makes them colourful Their name derives from the Ancient Greek word poluz (polus, meaning “many, much”) and the word phenol which refers to a chemical structure formed by attaching of a hydroxyl (—OH) group to an aromatic benzenoid (phenyl) ring as it is found in alcohols ( the -ol suffix, Quideau et al, 2011). The number and characteristics of these phenol structures underlie the unique physical, chemical, toxic, metabolic or pharmaceutical properties of the class members (Williams et al, 2004). These compounds are not polymers of phenol. The more com puting-demanding ab initio methods, e.g. complete active space self-consistent field (CASSCF) method (Andresson and Roos, 1995) or multi-reference configuration interaction (MRCI, Sherrill et al, 1999), are usually successful, but the quality of the obtained results is highly dependent on the selec-

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Results

Conclusion