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.

Experimental and Computational Investigations into Trivalent Phosphorous-Mediated Radical Thiol Desulfurization

Radical-mediated thiol desulfurization processes using tricoordinate phosphorous reagents are used in a range of applications from small molecule synthesis to peptide modification. A combined experimental and computational examination of the mechanism and kinetics of the radical desulfurization of alkyl thiyl radicals using trivalent phosphorus reagents was performed. Primary alkyl thiols undergo desulfurization between 10^6 to 10^9 M-1s-1 depending on the phosphorus component with either an H-atom transfer step or β-fragmentation of the thiophosphoranyl intermediate may be rate-controlling. While the desulfurization of primary aliphatic thiols showed a marked dependence on the identity of phosphorous reagent used with either a rate-controlling H-atom transfer or -fragmentation, thiols yielding stabilized C-centered radicals showed much less sensitivity. Support for a stepwise S-atom transfer process progressing via a distorted trigonal bipyramidal thiophosphoranyl radical intermediate was obtained from DFT calculated energetics and hyperfine splitting values.

PREPARATION OF ALKYLTHIOMETHYLATED DERIVATIVES OF 2,4-DI-TERT-BUTYLPHENOL AND PRELIMINARY ASSESSMENT OF THEIR ANTIOXIDANT ACTIVITY

This article discusses a method for the preparation of alkylthiomethyl derivatives of 2,4-di-tert-butylphenol through the interaction of the obtained Mannich bases with aliphatic thiols of various structures, as well as a preliminary assessment of the antioxidant activity by anodic voltammetry.

Synthetic Route of Trithiolato-Bridged Dinuclear Arene Ruthenium(II) Complexes [(η6-P-MeC6H4Pri)2Ru2(μ2-SR)3]+

Several dinuclear trithiophenolato-bridged arene ruthenium complexes [(η6-p-MeC6H4Pri)2Ru2(μ2-SC6H4-R)3]+ could so far only be obtained with moderate yields using the synthetic route established in the early 2000s. With much less reactive aliphatic thiols or with bulky thiols, the reactions become even less efficient and the desired trithiolato complexes are obtained either only with bad yields or not at all. We employ density functional theory (DFT) calculations to gain a fundamental understanding of the reaction mechanisms leading to the formation of trithiolato complexes starting from the dichloro(p-cymene)ruthenium(II) dimer [(η6-p-MeC6H4Pri)Ru(μ2-Cl)Cl]2. The results of this DFT study enable us to rationalize experimental results and allow us, via a modified synthetic route, to synthesize the previously unreported and hitherto considered as unrealistic trithiolato complex [(η6-p-MeC6H4Pri)2Ru2(μ2-SC6H11)3]+. Our DFT study opens possibilities for the synthesis of so far inaccessible thiolato-bridged dinuclear arene ruthenium(II) complexes but more generally also the synthesis of other thiolato-bridged dinuclear group 8 and 9 metal com-plexes could be reexamined.

Development of a 1,3a,6a-triazapentalene derivative as a compact and thiol-specific fluorescent labeling reagent

For the fluorescence imaging of biologically active small compounds, the development of compact fluorophores that do not perturb bioactivity is required. Here we report a compact derivative of fluorescent 1,3a,6a-triazapentalenes, 2-isobutenylcarbonyl-1,3a,6a-triazapentalene (TAP-VK1), as a fluorescent labeling reagent. The reaction of TAP-VK1 with various aliphatic thiols proceeds smoothly to afford the corresponding 1,4-adducts in high yields, and nucleophiles other than thiols do not react. After the addition of thiol groups in dichloromethane, the emission maximum of TAP-VK1 shifts to a shorter wavelength and the fluorescence intensity is substantially increased. The utility of TAP-VK1 as a compact fluorescent labeling reagent is clearly demonstrated by the labeling of Captopril, which is a small molecular drug for hypertension. The successful imaging of Captopril, one of the most compact drugs, in this study demonstrates the usefulness of compact fluorophores for mechanistic studies.

Intermolecular Phosphite-Mediated Radical Desulfurative Alkene Alkylation Using Thiols

<div><div><div><p>We report herein the development of an S-atom transfer process using triethyl phosphite as the S-atom acceptor that allows thiols to serve as precursors of C-centered radials. A range of functionalized and electronically unbiased alkenes including those containing common heteroatom-based functional groups. This process is driven by the exchange of relatively weak S-H and C-S bonds of aliphatic thiols for C-H, C-C, and S-P bonds of the products formed.</p></div></div></div>