Infrared Spectrum of the H3N−HCl Complex in Solid Ne, Ne/Ar, Ar, and Kr. Matrix Effects on a Strong Hydrogen-Bonded Complex

Ammonia and hydrogen chloride vapors from thermal decomposition of NH 4 Cl co-deposited with excess neon at 4−5 K formed the H 3 N−HCl complex. Strong, broad 2084 cm -1 and strong, sharp 1060.2 cm -1 absorptions are assigned to the H−Cl stretching and symmetric NH 3 bending modes and weaker 2017.4 and 708.9 cm -1 bands to the overtone of the NH 3 mode and the H−Cl librational fundamental of the 1:1 complex. Complementary experiments were done with neon/argon mixtures, argon, and krypton to investigate the 1:1 complex in a range of matrix environments. Vibrational assignments are supported by 15 NH 4 Cl, ND 4 Cl, and 15 ND 4 Cl isotopic substitution. The neon matrix spectrum suggests a strong hydrogen bond, slightly stronger than in the gas-phase complex, but not as strong as found in the argon and krypton matrix hosts owing to increased solvation by the more polarizable matrix atoms.