Theoretical investigation of the interaction between 2-pyridone/2-hydroxypyridine and ammonia

The structures and harmonic vibrational frequencies of the closed complexes 2-pyridone-NH3 (2PY-NH3), 2-hydroxypyridine-NH3 (2HP-NH3), 2-pyridone-(NH3)(2) (2PY -(NH3)(2)), and 2-hydroxypyridine - (NH3)(2) (2HP-(NH3)(2)) were studied using the density functional theory (DFT). The final energies of each complex were obtained using the B3-LYP and MP2 methods. The NH3 molecule is both a proton donor and a proton acceptor in the 2PY-NH3 and 2HP-NH3 complexes, while in the 2PY-(NH3)(2) and 2HP-(NH3)(2) systems, the ammonia dimer acts both as a proton donor and a proton acceptor. Comparison is made between the theoretical results and recent experimental results for the 2PY-NH3 and 2PY-(NH3)(2) complexes. In the heterotrimer complexes, the cooperative effects are substantial and this is reflected by the intermolecular distance of the ammonia dimer, by the elongation of the NH bond length, by the frequency shift of the nu(NH) mode, and by the additive interaction energy.