Unprecedented observation and characterization of sulfur-centred bifurcated hydrogen bonds

Abstract

It is observed that the sulfur atom can unprecedentedly serve as a good acceptor to form the O–H⋯S⋯H–O bifurcated H-bond.

Water oxidation by Brønsted acid-catalyzedin situgenerated thiol cation: dual function of the acid catalyst leading to transition metal-free substitution and addition reactions of S–S bonds

“…The following configuration adjustment of 14a or 14a′ to 15a or 15a′ may then take place to afford thiol cation 10a , meanwhile releasing free 4a′ and 4a (steps ii–v). Next, the reaction of 2-PyS + ( 10a ) with water is more likely promoted by the basic pyridyl group or one of the S atoms of 1a to firstly give complex 16a or 16a′ (complex of 10a , H 2 O, and 1a , possibly formed via an S + ⋯O coordination bond and an OH⋯N or OH⋯S hydrogen bond) 22 and then by forming new S–O and new H–N or H–S bonds to give complex 17a or 17a′ bearing new O⋯HN or O⋯HS hydrogen bond (steps vi–vii). The DFT study also revealed that 17a is more stable and more easily formed than 17a′ as N is known to be basic than S. Then, by releasing 1a-H + or 1a-H + ′ , sulfenic acid 11a was generated from 17a or 17a′ (step viii).…”

“…The S–S bond of 1a-H + or 1a-H + ′ may then heterolytically cleave to give thiol cation PyS + 10a and thiopyridone 4a′ (which then tautomerizes to thiol 4a ) or directly thiol 4a . Then, promoted by the basic pyridyl group or one of the S atoms of disulfide 1a via S + ⋯O coordination and the formation of the OH⋯N or OH⋯S hydrogen bond 22 (complex 16a and 16a′ of Fig. 1), 10a may react with water to give complex 17a or 17a′ .…”

Differing Effects of Nonlinearity around the Proton Acceptor on CH··O and NH··O H-Bond Strength within Proteins

“…While the work described here focuses on NH..O and CH..O H-bonds, this type of bonding extends to a wide range of other atoms as well, including for example S and Se as both proton donor and acceptor − and C, , or even metal centers such as Au. − …”