SPECTROSCOPIC AND THEORETICAL-STUDIES OF THE COMPLEXES BETWEEN NITROUS-ACID AND AMMONIA

The complexes formed between cis- and trans-HONO isomers and ammonia h ave been observed and characterized in argon matrices. Five perturbed HONO vibrations and one perturbed NH3 deformation vibration were ident ified for the H3N...HONO-trans complex, and one perturbed HONO vibrati on and perturbed NH3 deformation vibration were identified for the H3N ...HONO-cis complex. The OH stretching vibration in the H3N...HONO-tra ns complex is ca. 800 cm(-1) red-shifted and NOH bending vibration is ca. 190 cm(-1) blue-shifted with respect to the trans-HONO monomer, in dicating formation of a very strong molecular hydrogen bond. Theoretic al studies of the structure and spectral characteristics of the H3N... HONO-trans and H3N...HONO-cis complexes were carried out on the electr on correlation level and G-311+G(2df,2pd) basis set. The calculated bi nding energy at the MP2 level is -40.13 and -36.39 kJ mol(-1) for the H3N...HONO-trans and H3N...HONO-cis complexes, respectively. The calcu lated spectra reproduce very well the frequencies and the intensities of the measured spectra.