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Yanai H, Terajima Y, Kleemiss F, Grabowsky S, Matsumoto T. Reversing the Bond Length Alternation Order in Conjugated Polyenes by Substituent Effects. Chemistry 2023; 29:e202203538. [PMID: 36515459 DOI: 10.1002/chem.202203538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 12/14/2022] [Accepted: 12/14/2022] [Indexed: 12/15/2022]
Abstract
We have synthesised several push-pull substituted conjugated polyenes and determined their accurate C-C bond lengths and charge-density distributions by utilising quantum crystallographic techniques. In a series of alkene, dienes, and triene bearing two (trifluoromethyl)sulfonyl (triflyl) groups on the terminal carbon atom, unique reversal of the bond-length alternation (BLA) order has been observed. This is a pronounced aberration from the molecular structure predicted by the Lewis-structure-based neutral resonance structure. Such reversal of BLA order has not been observed in push-pull compounds bearing conventional electron-withdrawing groups such as carbonyl and cyano groups instead of triflyl groups. Bonding behaviour of both normal and reversed bond length alternating systems has been revealed by complementary bonding analysis using several bond descriptors based on the experimentally fitted wavefunctions.
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Affiliation(s)
- Hikaru Yanai
- School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan
| | - Yoshihiko Terajima
- School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan
| | - Florian Kleemiss
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland.,Faculty of Chemistry and Pharmacy, University of Regensburg, Universitätsstr. 31, D-93053, Regensburg, Germany
| | - Simon Grabowsky
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland
| | - Takashi Matsumoto
- School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan
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Fugel M, Malaspina LA, Pal R, Thomas SP, Shi MW, Spackman MA, Sugimoto K, Grabowsky S. Revisiting a Historical Concept by Using Quantum Crystallography: Are Phosphate, Sulfate and Perchlorate Anions Hypervalent? Chemistry 2019; 25:6523-6532. [PMID: 30759315 DOI: 10.1002/chem.201806247] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Indexed: 11/05/2022]
Abstract
There are many examples of atoms in molecules that violate Lewis' octet rule, because they have more than four electron pairs assigned to their valence. These atoms are referred to as hypervalent. However, hypervalency may be regarded as an artifact arising from Lewis' description of molecules, which is based on the assumption that electrons are localized in two-center two-electron bonds and lone pairs. In the present paper, the isoelectronic phosphate (PO4 3- ), sulfate (SO4 2- ) and perchlorate (ClO4 - ) anions were examined with respect to the concept of hypervalency. Lewis formulas containing a hypervalent central atom exist for all three anions. Based on X-ray wavefunction refinements of high-resolution X-ray diffraction data of representative crystal structures (MgNH4 PO4 ⋅6 H2 O, Li2 SO4 ⋅H2 O, and KClO4 ), complementary bonding analyses were performed. In this way, experimental information from the new field of quantum crystallography validate long-known facts, or refute long-standing misunderstandings. It is shown that the P-O and S-O bonds are highly polarized covalent bonds and, thus, the increase in the valence population following three-center four-electron bonding is not sufficient to yield hypervalent phosphorus or sulfur atoms, respectively. However, for the highly covalent Cl-O bond, most bonding indicators imply a hypervalent chlorine atom.
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Affiliation(s)
- Malte Fugel
- Department 2-Chemistry/Biology, Institute of Inorganic Chemistry and Crystallography, University of Bremen, Leobener Str. 3 and 7, 28359, Bremen, Germany
| | - Lorraine A Malaspina
- Department 2-Chemistry/Biology, Institute of Inorganic Chemistry and Crystallography, University of Bremen, Leobener Str. 3 and 7, 28359, Bremen, Germany
| | - Rumpa Pal
- Department 2-Chemistry/Biology, Institute of Inorganic Chemistry and Crystallography, University of Bremen, Leobener Str. 3 and 7, 28359, Bremen, Germany.,Current address: Division of Physics, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8571, Japan
| | - Sajesh P Thomas
- School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Perth, WA, 6009, Australia.,Current address: Interdisciplinary Nanoscience Center - INANO-Kemi, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark
| | - Ming W Shi
- School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Perth, WA, 6009, Australia
| | - Mark A Spackman
- School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Perth, WA, 6009, Australia
| | - Kunihisa Sugimoto
- SPring-8, Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5198, Japan
| | - Simon Grabowsky
- Department 2-Chemistry/Biology, Institute of Inorganic Chemistry and Crystallography, University of Bremen, Leobener Str. 3 and 7, 28359, Bremen, Germany
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