Controlled stabilization of anionic forms of the uracil derivatives: A DFT study

Margarita G Ilyina; Edward M Khamitov; Akhat G Mustafin; S L Khursan

doi:10.1016/j.jmgm.2017.11.007

Controlled stabilization of anionic forms of the uracil derivatives: A DFT study

J Mol Graph Model. 2018 Jan:79:65-71. doi: 10.1016/j.jmgm.2017.11.007. Epub 2017 Nov 11.

Authors

Margarita G Ilyina¹, Edward M Khamitov², Akhat G Mustafin³, S L Khursan⁴

Affiliations

¹ Bashkir State University, Department of Chemistry, Chair of Physical Chemistry and Chemical Ecology, 32 Zaki Validi Str., Ufa 450074, Russia; Institute of Petroleum Refining and Petrochemistry, Laboratory of Quantum Chemistry and Molecular Dynamics of the Department of Chemistry and Technology, 12 Initsiativnaya Str., Ufa 450065, Republic of Bashkortostan, Russia. Electronic address: margarita.kondrova@yandex.ru.
² Bashkir State University, Department of Chemistry, Chair of Physical Chemistry and Chemical Ecology, 32 Zaki Validi Str., Ufa 450074, Russia; Ufa Institute of Chemistry, Russian Academy of Sciences, Laboratory of Chemical Physics, 69 Prospekt Oktyabrya, Ufa 450054, Russia; Institute of Petroleum Refining and Petrochemistry, Laboratory of Quantum Chemistry and Molecular Dynamics of the Department of Chemistry and Technology, 12 Initsiativnaya Str., Ufa 450065, Republic of Bashkortostan, Russia.
³ Bashkir State University, Department of Chemistry, Chair of Physical Chemistry and Chemical Ecology, 32 Zaki Validi Str., Ufa 450074, Russia; Ufa Institute of Chemistry, Russian Academy of Sciences, Laboratory of Chemical Physics, 69 Prospekt Oktyabrya, Ufa 450054, Russia.
⁴ Ufa Institute of Chemistry, Russian Academy of Sciences, Laboratory of Chemical Physics, 69 Prospekt Oktyabrya, Ufa 450054, Russia.

PMID: 29145035
DOI: 10.1016/j.jmgm.2017.11.007

Abstract

Relative stabilities of the N1/N3/О5/О6 anions of 42 substituted uracils in gas phase and aqueous solutions have been theoretically studied using approximation IEFPCM (SMD) - TPSS/aug-cc-pVTZ. The specific solvation of uracil and its anions has been simulated with the first hydrate shell made up with 5 water molecules. The nonspecific solvation has been accounted in terms of the SMD model. We have found a series of relative stability under conditions of both specific and nonspecific hydration. The series is ranked according to the increase of the relative stability of the N3 anion. In gas phase, the N1 anion is significantly more stable than its N3 counterpart: the ΔG_gas values vary in the range from 19.54 (5OH6СН₃U) to 83.14 (5NO₂6NH₂U) kJ/mol that is caused by a more effective delocalization of the excess charge through the uracil framework in the N1 anion. The hydration pronouncedly diminishes ΔG to the range from -0.02 (5OH6СН₃U) to 38.16 (5Br6NO₂U) kJ/mol due to the fact that the polar solvent is prone to stabilize more polar anionic states of uracils. Therefore, less polar uracil anions are more stable. We have defined the main factor influencing the N1/N3/О5/О6 distribution of anions, viz. the presence of the substituents in 5 and 6 positions of the pyrimidine ring. Herewith, the most favorable mechanism of the influence of 5-substituents has been previously defined as resonant whereas, as we found in this work, the inductive mechanism is more pronounced in the case of 6-substituents.

Keywords: Anions; Density functional theory; Influence of substituents; Polarity; Solvation; Stabilization; Uracil.

MeSH terms

Anions / chemistry*
Density Functional Theory
Models, Molecular
Molecular Conformation
Phase Transition
Solutions
Structure-Activity Relationship
Uracil / analogs & derivatives*
Uracil / chemistry*

Substances

Anions
Solutions
Uracil