Matrix-isolation FT-IR studies and ab-initio calculations of hydrogen-bonded complexes of molecules modeling cytosine or isocytosine tautomers. 2. 4-Aminopyridine and 4-aminopyrimidine complexes with H2O in Ar matrices

Johan Smets, Ludwik Adamowicz, Guido Maes

Research output: Contribution to journalArticle

63 Scopus citations

Abstract

H-bonding interactions of the cytosine-modeling compounds 4-aminopyridine and 4-aminopyrimidine with water are investigated with the use of a combined experimental matrix-isolation FT-IR and theoretical ab-initio method. Both bases appear exclusively as the amino tautomers in low-temperature Ar matrices, in accordance with large ab-initio predicted energy differences with the rare imino forms. The most stable complex of water with 4-aminopyridine is the H-bonded N1⋯HO-H structure, but the energy difference with the alternative N-H⋯OH2 complex is calculated to be only 6.7 kJ/mol. Both complexes are observed in the Ar matrix. In the case of 4-aminopyrimidine, the closed N-H⋯O-H⋯N3 structure containing two H-bonds is found to be significantly more stable than the singly H-bonded structures N1⋯HO-H and N-H⋯OH2 by 8.0 and 10.2 kJ/mol, respectively. The previously suggested relation between the scaling factor for the theoretically-calculated vbOH mode of the H-bonded water and the proton affinity value of the proton-acceptor site in the base is developed further.

Original languageEnglish (US)
Pages (from-to)6387-6400
Number of pages14
JournalJournal of physical chemistry
Volume99
Issue number17
DOIs
StatePublished - Jan 1 1995

ASJC Scopus subject areas

  • Engineering(all)
  • Physical and Theoretical Chemistry

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