Ultraviolet and infrared spectroscopy of matrix-isolated 7-azaindole dimer: Matrix effect on excited state tautomerization

► First photophysical study of matrix-isolated 7-azaindole homodimer (7AI2). ► IR spectra of the matrix-isolated 7AI2 has also been measured for the first time. ► Matrix-isolated IR spectrum of 7AI2 looks identical to that of the jet-cooled dimer. ► Excited state tautomerization of 7AI2 is fully inhibited in Ar and N2 matrixes.