Structural assignment of adenine aggregates in $CDCl3$ Available to Purchase

We reinvestigated the self-association of 9-substituted adenine derivatives in $CDCl3$ solutions and present the infrared spectra of 9-ethyladenine and $N$-methyl-9-ethyladenine and its aggregates in the spectral regions between 1500 and $1800cm−1$ and between 2700 and $3600cm−1$⁠. Wavelength dependent absolute extinction coefficients of the monomer and dimers are presented on the basis of a simple deconvolution method. Comparison of the deconvoluted dimer spectra with quantum chemical calculations allows for a structural assignment of the two dimer structures that coexist in 9-ethyladenine/$CDCl3$ solutions. In contrast, the dimer spectrum of $N$-methyl-9-ethyladenine is dominated by a single isomer.