Dispersion-Dominated S-H···Se H-Bonds in the Dimethyl Selenide-H

The S-H···Se H-bonded complex formation between dimethyl selenide (Me2Se) and H2S was studied using Fourier transform infrared (FTIR) spectroscopy in a cold and solid nitrogen (N2) matrix. Concentration variation and annealing experiments confirmed the formation of the binary Me2Se-H2S complex along with larger (1:2 and 2:1) clusters. The S-H···Se H-bonded binary complex exhibited a large red shift of 146.3 cm-1 in the νS-H mode of H2S. However, the magnitude of the spectral shifts decreased in the larger complexes (113.8-134.2 cm-1). The binary Me2Se-H2S complex was further stabilized, and the νS-H transition was even more red-shifted (153.4 cm-1) due to cooperative strengthening of the existing S-H···Se H-bonds by N2 molecules forming weak S-H···N H-bonds along with S···N or Se···N van der Waals interactions. The binary Me2Se-H2S complex bound by S···Se van der Waals interactions was found to be ∼0.6 kcal mol-1 less stable than its S-H···Se H-bonded counterpart and could not be identified in the matrix spectra. The binding energy of the S-H···Se H-bonded Me2Se-H2S complex was found to be 3.7 kcal mol-1. The N2-bound ternary complex exhibited an increased binding energy of 5.2 kcal mol-1. Furthermore, the binding energies of the two Me2Se-(H2S)2 (1:2) and (Me2Se)2-H2S (2:1) complexes were 6.7, 7.1, and 8.3 kcal mol-1, respectively. The S-H···Se H-bonds in the Me2Se-H2S complex were found to be more than twice as strong, considerably shorter, and more dispersion-stabilized than the S-H···S H-bond in H2S dimer.