Nature and strength of sulfur-centred hydrogen bonds: laser spectroscopic investigations in the gas phase and quantum-chemical calculations

Abstract

The importance of Sulfur centred hydrogen bonds (SCHBs) cannot be underestimated given the current day knowledge of its non-covalent interactions prevalent in many biopolymers as well as in organic systems. Based on the distance/angle constraints available from the structural database, these interactions have been interchangeably termed as van der Waals/hydrogen bonded complexes. There is a lack of sufficient spectroscopic evidence that can unequivocally term these interactions as hydrogen bonding interactions. In this review we present laser spectroscopic investigations of isolated binary complexes of H-bond donor-acceptor molecules containing Sulfur atom. The complexes were formed using supersonic jet expansion method and the IR/UV spectroscopic investigations were carried out on mass selected binary complexes. The pertinent questions regarding SCHBs addressed herein are (1) Is electronegativity the controlling factor to be a potent H-bond donor/acceptor? (2) How do SCHBs compare with their oxygen counterpart? (3) What is the nature of SCHBs, i.e. what are the dominating forces in stabilising these hydrogen bonds? (4) Do SCHBs follow classical H-bond acid–base formalism? (5) Are SCHBs found in peptides and proteins? If so, what are their strengths? Do they control the structure of the peptides? The experimental investigations were also supported by high level of ab initio computations.

Keywords:

• Sulfur centred hydrogen bond
• hydrogen sulphide
• methionine
• phenylalanine
• dipeptides
• ZEKE spectroscopy
• Birge–Sponer
• S–H⋯O interaction
• O–H⋯S interaction
• N–H⋯S interaction
• S–H⋯π interaction

Acknowledgements

HSB acknowledges the financial support from the French National Research Agency (ANR) (Grant ANR-08-BLAN-0158-01) and the ‘Triangle de la Physique’ Foundation (Grant 2008-053TSERPBIO) for the work carried out in Ref. [113]. AB acknowledges the partial support by the Grant-in-Aid for Scientific Research (Project No. 26108504 on Innovative Area [2507] from MEXT Japan and No. 26288002 from JSPS) for the work carried out in Refs. [136] and [159]. Rest of the work was supported by the TIFR, India.

Additional information

Funding

Most of the work reported in this review was supported by TIFR, India. The work reported in Ref. 113 was supported by the French National Research Agency (ANR) [grant number ANR-08-BLAN-0158-01] and the ‘Triangle de la Physique’ Foundation [grant number 2008-053TSERP-BIO]. The work reported in Ref. 136 and 159 was supported by the Grant-in-Aid for Scientific Research [project number 26108504 on Innovative Area [2507] from MEXT Japan and number 26288002 from JSPS].