MOLECULAR-STRUCTURE AND INFRARED-SPECTRA OF ADENINE - EXPERIMENTAL-MATRIX ISOLATION AND DENSITY-FUNCTIONAL THEORY STUDY OF ADENINE N-15 ISOTOPOMERS

The infrared spectra of matrix-isolated adenine and its N-15 isotopome rs with N-15 at the N(9) or N(7) positions have been studied. The expe rimentally observed IR spectra were compared with the spectra predicte d at the DFT(B3-LYP)/6-31G(d,p) level. This method was also used to ca lculate molecular parameters (rotational constants, dipole moments) of both N(9)H and N(7)H tautomers of adenine. The agreement between expe rimental and theoretical spectral positions, intensities, and isotopic shifts of the IR bands is good. That allows for reliable assignment o f the IR spectra and for conclusion that the amino-N(9)H tautomer of a denine strongly dominates in low-temperature matrices.