Evidence of sulfur centered hydrogen bond with sulfur atoms as a donor in aromatic thiols and aliphatic thiols on complexation with water using quantum mechanical methods

It has been more than a century since the discovery of hydrogen bonds, but the knowledge about its impact on day to day life of people is getting enhanced even now. It has a pivotal role in the stabilization of various biomolecules and subsequent bioactivity. Sulfur cantered hydrogen bond (SCHB), which is a weak interaction, has attracted the attention of many scientists in the last few decades. In this work, we report the nature of the SCHB between aliphatic/aromatic thiols and water. B3LYP-D3(BJ) with cc-pVTZ level was used for modeling the hydrogen bonded thiol-water complexes. Domain-based local pair natural orbitals coupled-cluster theory with single, double, and perturbative triple excitation DLPNO-CCSD(T) method was used for local energy decomposition analysis. QTAIM analysis helped to examine hydrogen bonds, weak non-covalent interactions, and the various electron density delocalization. Natural Bond Orbital (NBO) analysis explains the reason for the sulfur atom being the H-bond donor. Second-order perturbation energy from NBO findings supports the data obtained by LED and AIM calculations. Aromatic thiols form stronger hydrogen bonds than aliphatic thiols. The effect of substituents was also explored by studying aromatic systems with electron-withdrawing groups and donating groups. EDG substituted have more vital interaction, and EWG substituted thiols form stronger S-H…O hydrogen bonds.