Spontaneous tunneling and near-infrared-induced interconversion between the amino-hydroxy conformers of cytosine

Reva I., Nowak M. J., Lapinski L., Fausto R.

JOURNAL OF CHEMICAL PHYSICS, vol.136, no.6, 2012 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 136 Issue: 6
  • Publication Date: 2012
  • Doi Number: 10.1063/1.3683217
  • Journal Name: JOURNAL OF CHEMICAL PHYSICS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Istanbul Kültür University Affiliated: Yes

Abstract

Spontaneous and near-infrared/infrared (NIR/IR)-induced interconversions between two aminohydroxy conformers of monomeric cytosine have been investigated for the compound isolated in a low-temperature argon matrix. Combined use of a laser source (which provides narrowband NIR radiation) and a broadband NIR/IR source of excitation light allowed a detailed investigation of mutual conversions of the two conformers in question. The experiments carried out within the current work demonstrated that upon broadband NIR/IR irradiation (with the IR source of FTIR spectrometer) the population ratio of the two amino-hydroxy conformers changes towards a ratio corresponding to a photostationary state. Evolution of the conformer population ratio towards the photostationary ratio occurred independent of the initial ratio of conformers, which could be prepared by a population shift (in favor of one of the forms) induced by narrowband NIR excitation. Moreover, spontaneous tunneling conversion of the higher-energy conformer into a lower-energy form was observed for cytosine isolated in a low-temperature argon matrix kept in the dark. This process is slow and occurs on a time scale of days. The tunneling process, studied for matrix-isolated cytosine, clearly follows a dispersive type of kinetics rather than the classical monoexponential kinetics. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3683217]