Not so common hydrogen bond donor ability of ammonia is explored with three different acceptors using matrix isolation technique. 1 : 1 complex of [NH3-Se(CH3)2] shows the maximum red-shift followed by [NH3-S(CH3)2] and [NH3-O(CH3)2], although the stability of the three complexes are almost equal. Change in occupancy of the lone pair in the chalcogen atom and the anti-bonding N-H orbital is proportional to the observed red-shift.
Ammonia is an important molecule due to its wide use in the fertiliser industry. It is also used in aminolysis reactions. Theoretical studies of the reaction mechanism predict that in reactive complexes and transition states, ammonia acts as a hydrogen bond donor forming N−H⋅⋅⋅O hydrogen bond. Experimental reports of N−H⋅⋅⋅O hydrogen bond, where ammonia acts as a hydrogen bond donor are scarce. Herein, the hydrogen bond donor ability of ammonia is investigated with three chalcogen atoms i. e. O, S, and Se using matrix isolation infrared spectroscopy and electronic structure calculations. In addition, the chalcogen bond acceptor ability of ammonia has also been investigated. The hydrogen bond acceptor molecules used here are O(CH3)2, S(CH3)2, and Se(CH3)2. The formation of the 1 : 1 complex has been monitored in the N−H symmetric and anti-symmetric stretching modes of ammonia. The nature of the complex has been delineated using Atoms in Molecules analysis, Natural Bond Orbital analysis, and Energy Decomposition Analysis. This work presents the first comparison of the hydrogen bond donor ability of ammonia with O, S, and Se.Zum Volltext