A unified cost-effective method for the construction of reliable potential energy surfaces for H2S and H2O clusters

Matrix Isolation IR Spectroscopic Investigation of S-H···S-S H-Bond in H2S-Diethyl Disulfide Complex

S-H···S-S H-bonded 1:1 diethyl disulfide (DEDS)-H2S complexes have been investigated by using FTIR spectroscopy in cold, solid argon (Ar) and nitrogen (N2) matrices. H2S was found to form one or two S-H···S-S H-bonds with the DEDS molecule, while H2O is known to form only a single O-H···S-S H-bond. A total of five distinct H-bonded complexes have been identified for the two lowest energy rotamers of DEDS: three with the most stable GGG conformer and two with GGG'. Their binding energies varied from 2.43 to 3.05 kcal mol-1. All five binary complexes were observed in the N2 matrix, while only three complexes of GGG conformer could be identified in the Ar matrix as relative energy of GGG' is known to increase significantly in the presence of Ar. Activation barriers for interconversion of the five binary complexes were calculated and were found to vary from 0.08 to 2.65 kcal mol-1. S-S linkage in DEDS has been found to be a more efficient acceptor for S-H H-bond donor than the S atom in H2S. Dispersion interaction plays a major role toward overall stabilization of the H-bonded complexes and was found to be on the higher side among all sulfur-centered H-bonds studied until now.

Competition between C-H⋯S and S-H⋯Cl H-bonds in a CHCl3-H2S complex: a combined matrix isolation IR spectroscopic and quantum chemical investigation

H-bonded complexes between CHCl3 and H2S have been studied in a cold and inert argon matrix using IR spectroscopy. Both molecules were found to act as both a H-bond donor and acceptor, resulting in two different conformers. The more stable one (binding energy 3.25 kcal mol-1) was bound by a C-H⋯S H-bond, while the less stable one (1.90 kcal mol-1) by a S-H⋯Cl H-bond. The H-bonded complex formation has been confirmed by monitoring the spectral changes in νC-H and νS-H fundamental vibrations. The νC-H mode exhibited red shifts by 22.7 cm-1 upon C-H⋯S H-bond formation, while the formation of a S-H⋯Cl H-bond resulted in 24.2 and 25.4 cm-1 red shifts in the νS-H modes. The barrier for conversion of the less stable conformer to the more stable one was found to be 0.6 kcal mol-1. The rigid matrix environment prevented any detectable population transfer that required significant relative movement of the monomeric moieties. Dispersion interaction was found to significantly contribute to the overall stabilization of both conformers, more so for the S-H⋯Cl H-bonded one.

Revisiting the IR Spectra of H2S in an Argon Matrix: Identification of (H2S)n (n ≤ 4) Clusters via the Spectral Assignment of νS-H Transitions

Small-molecular clusters of H2S up to tetramer have been experimentally identified in a cold and solid argon matrix by the spectral assignment of νS-H fundamental transitions for different H2S:argon mixing ratios. Normal-mode frequency calculations at the MP2-CP/aug-cc-pV(Q + d)Z level have been used to support the spectral assignments. In addition, modulations in relative populations of different clusters due to the annealing of the deposited matrix and the preheating of the H2S-argon gas mixture before deposition reinforced the spectral assignments. Variations in mixing ratio, annealing of the matrix, and preheating of the gas mixture have also been used, in a combined manner, to unambiguously identify the ν1 and ν3 bands of the H2S monomer, which has been a matter of dispute for a long period. The two bands have been identified at 2634.4 and 2648.0 cm-1, respectively, while three bands at 2581.5, 2568.4, and 2547.6 cm-1 have been assigned to H-bonded dimers, cyclic trimers, and cyclic tetramers, respectively. Multiple bands within 2550-2580 cm-1 have been assigned to caged tetramers. The cooperative strengthening of S-H···S H bonds in cyclic H2S clusters was evident from the linear increment in νS-H spectral shifts with cluster size.