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Triel Bond Formed by Malondialdehyde and Its Influence on the Intramolecular H-Bond and Proton Transfer

by Qiaozhuo Wu, Shubin Yang and Qingzhong Li

Molecules 2022, 27(18), 6091; https://doi.org/10.3390/molecules27186091 - 18 Sep 2022

Cited by 5 | Viewed by 1740

Malondialdehyde (MDA) engages in a triel bond (TrB) with TrX₃ (Tr = B and Al; X = H, F, Cl, and Br) in three modes, in which the hydroxyl O, carbonyl O, and central carbon atoms of MDA act as the electron donors, respectively. A H···X secondary interaction coexists with the TrB in the former two types of complexes. The carbonyl O forms a stronger TrB than the hydroxyl O, and both of them are better electron donors than the central carbon atom. The TrB formed by the hydroxyl O enhances the intramolecular H-bond in MDA and thus promotes proton transfer in MDA-BX₃ (X = Cl and Br) and MDA-AlX₃ (X = halogen), while a weakening H-bond and the inhibition of proton transfer are caused by the TrB formed by the carbonyl O. The TrB formed by the central carbon atom imposes little influence on the H-bond. The BH₂ substitution on the central C-H bond can also realise the proton transfer in the triel-bonded complexes between the hydroxyl O and TrH₃ (Tr = B and Al). Full article

(This article belongs to the Special Issue Chemical Bond and Intermolecular Interactions)

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15 pages, 1187 KiB

Open AccessArticle

Competition between Intra and Intermolecular Triel Bonds. Complexes between Naphthalene Derivatives and Neutral or Anionic Lewis Bases

by Wiktor Zierkiewicz, Mariusz Michalczyk and Steve Scheiner

Molecules 2020, 25(3), 635; https://doi.org/10.3390/molecules25030635 - 1 Feb 2020

Cited by 21 | Viewed by 3707

Abstract

: A TrF₂ group (Tr = B, Al, Ga, In, Tl) is placed on one of the α positions of naphthalene, and its ability to engage in a triel bond (TrB) with a weak (NCH) and strong (NC⁻) nucleophile is assessed by ab initio calculations. As a competitor, an NH₂ group is placed on the neighboring C^α, from which point it forms an intramolecular TrB with the TrF₂ group. The latter internal TrB reduces the intensity of the π-hole on the Tr atom, decreasing its ability to engage in a second external TrB. The intermolecular TrB is weakened by a factor of about two for the smaller Tr atoms but is less severe for the larger Tl. The external TrB can be quite strong nonetheless; it varies from a minimum of 8 kcal/mol for the weak NCH base, up to as much as 70 kcal/mol for CN⁻. Likewise, the appearance of an external TrB to a strong base like CN⁻ lessens the ability of the Tr to engage in an internal TrB, to the point where such an intramolecular TrB becomes questionable. Full article

(This article belongs to the Special Issue Structural Changes in Supramolecular Complexes)

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