Can anion interaction accelerate transformation of cytosine tautomers? Detailed view form QTAIM analysis

摘要: The relative stabilities and noncovalent interactions of the six low-lying energy tautomers cytosine nucleobase with some biological anions (such as F−, Cl−, CN−) have been investigated in gas phase by density functional theory (DFT) method conjunction 6-311++G (d,p) atomic basis set. Furthermore, to systematically investigate all possible tautomerisms from induced proton transfer, we describe a study structural tautomer interconversion continuum solvent using DFT calculation. We carried out geometrical optimizations integral equation formalism polarizable (IEF-PCM) model account for effect, results were compared those phase. result calculation revealed that bind mostly bidentate manner via hydrogen bond, stabilization energies these complexes are larger than case when monodentate manner. quantum atoms molecules (QTAIM), natural bonding orbital (NBO) decomposition analysis (EDA) also applied understand nature bond complexes. NBO reveals interaction patterns between σ-type lone pairs \( \sigma_{{_{{{\text{N}}--{\text{H}}}} }}^{*} \), \sigma_{{_{{{\text{O}}--{\text{H}}}} \) \sigma_{{_{{{\text{H}}--{\text{F}}}} antibonding orbitals. Also, according theories, found be partially electrostatic covalent. EDA identify bonds less 35% covalent character more 65% electrostatic, increases different order F− > CN− Cl−. On other hand, anion Cl− lower CN−anions imply charge transfer stronger ionic character. relationship (E2) (EH···X) electron (ρ(r)) investigated.