Similar Strength of the NH···O and NH···S Hydrogen Bonds in Binary Complexes

The weakly interacting complexes of dimethylamine with dimethyl ether (DMA–DME) and with dimethylsulfide (DMA–DMS) have been detected in the gas phase using Fourier transform infrared spectroscopy at room temperature. The observed redshift of the fundamental NH-stretching frequency was found to be extremely small with only 5 and 19 cm^–1 for DMA–DME and DMA–DMS, respectively. The experimentally determined integrated absorbance has been combined with a calculated oscillator strength to determine an equilibrium constant of 2 × 10^–3 and 4 × 10^–3 for the DMA–DME and DMA–DMS complexes, respectively. The topological analyses reveal that several hydrogen bond interactions are present in the complexes. The calculated binding energies, geometric parameters, observed redshifts, and topological analyses suggest that oxygen and sulfur are hydrogen bond acceptors of similar strength.