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 NH4Cl co-deposited with excess neon at 4−5 K formed the H3N−HCl complex. Strong, broad 2084 cm-1 and strong, sharp 1060.2 cm-1 absorptions are assigned to the H−Cl stretching and symmetric NH3 bending modes and weaker 2017.4 and 708.9 cm-1 bands to the overtone of the NH3 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 15NH4Cl, ND4Cl, and 15ND4Cl 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.