Isomer selective IR experiments and correlated ab initio quantum chemical calculations support planar H-bonded structure of the 7-methyl adenine⋯adenine and stacked structure of the 9-methyl adenine⋯adenine base pairs

Abstract

In this paper we show that the stacked structures of 9-methyl adenine⋯adenine are comparably stable as the most stable hydrogen bonded structures and that the calculated IR pattern of the stacked structures is in a very good agreement with the experimental spectrum. The pair 7-methyl adenine⋯adenine on the other hand shows a nearly planar hydrogen bond arrangement and no stacked structure was observed.