A complex is assembled which pairs a carboxyl group of X 1 COOH with a 1,2,5-chalcogenadiazole ring containing substituents on its C atoms. The OH of the carboxyl group donates a proton to a N atom of the ring to form a OH⋯N H-bond (HB), while its carbonyl O engages in a Y⋯O chalcogen bond (ChB) with the ring in which Y = S, Se, Te. The ChB is strengthened by enlarging the size of the Y atom from S to Se to Te. Placement of an electron-withdrawing group (EWG) X 1 on the acid strengthens the HB while weakening the ChB; the reverse occurs when EWGs are placed on the ring. By selection of the proper substituents on the two units, it is possible to achieve a near perfect balance between the strengths of these two bonds. These bond strengths are also reflected in the NMR spectroscopic properties of the chemical shielding of the various atoms and the coupling between the nuclei directly involved in each bond.
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Participation of S and Se in hydrogen and chalcogen bonds
This article reviews the history and the current state of knowledge concerning the ability of the heavy chalcogen atoms S and Se, and to some extent Te, to participate in a H-bond as either proton donor or acceptor. These atoms are nearly as effective proton acceptors as O, and only slightly weaker as donor. They can also participate in chalcogen bonds where they act as electron acceptors from a nucleophile. These bonds rapidly strengthen as the chalcogen atom becomes larger: S < Se < Te, or if they are surrounded by electron-withdrawing substituents, and can exceed that of many types of H-bonds. Experimental and computational evidence indicates that both H-bonds and chalcogen bonds involving S and Se occur widely in chemical and biological systems, and play an active role in structure and function.
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- Award ID(s):
- 1954310
- NSF-PAR ID:
- 10326169
- Date Published:
- Journal Name:
- CrystEngComm
- Volume:
- 23
- Issue:
- 39
- ISSN:
- 1466-8033
- Page Range / eLocation ID:
- 6821 to 6837
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D1CE01046H
