Bifurcated Chalcogen Bonds Based on One σ-Hole

Abstract

Chalcogen bonds are noncovalent interactions and are increasingly coming into focus for the design of complex structures in research areas such as crystal engineering, molecular recognition and catalysis. Conceptionally, chalcogen bonds can be considered as interaction between one σ-hole and one Lewis base center. Herein, we analyze the interaction between bidentate chelating ligands having two nucleophilic centers with one single σ-hole of a chalcogenazole (two-lone-pair/one-σ-hole interactions). Referring to this, we show by quantum chemical calculations and X-ray studies that three bond types are possible: in the first case, a chalcogen bond is formed between the σ-hole and only one of the Lewis base centers. In the second case, a strong bond is formed by one nucleophilic center; the second center provides only a small amount of additional stabilization. In the third case, two equivalent bonds to the σ-hole are formed by both Lewis base centers. According to the calculations the bifurcated bonds are stronger than simple chalcogen bonds and lead to a more rigid molecule arrangement in the complex.

Selective Activation of Chalcogen Bonding: An Efficient Structuring Tool toward Crystal Engineering Strategies

“…In order to recover with ChB the same degree of predictability, we concentrated our efforts toward chalcogenated molecules with two dif ferent substituents on the chalcogen atom, and only one of them with a strong electron-withdrawing character (Figure 2a). 19 Under these circumstances, we expect a differentiation of the two σ-holes up to a point where the strongest one will essentially control the supramolecular organization of cocrystals, in a way similar to that observed with XB. As illustrated in Figure 2b, this approach has been already used in cationic ChB donors aimed at interacting with different neutral or anionic Lewis bases toward anion recognition effects or organo-catalysis applications.…”

Fluorogenic In Situ Thioacetalization: Expanding the Chemical Space of Fluorescent Probes, Including Unorthodox, Bifurcated, and Mechanosensitive Chalcogen Bonds

“…The longest chalcogen bond d = 3.38 Å of 13 coincided with the weakest NBO electron transfer contribution of E ET = 0.28 kcal mol –1 , while the push–pull dipole remained very high at μ = 10.5 D and planarization with E rel = +1.69 kcal mol –1 was least disfavored (Figure c and Table , entry 7). This apparent contradiction could be understood with the highest conformational rigidity of the 1,3-dithiane chair, which positions both sulfur atoms at almost equal distance for a formal bifurcated − three-center chalcogen bond, where long distances are compensated by doubled interactions ( d 1 = 3.39 Å and d 2 = 3.46 Å, Figure f,g). The existence and attractive nature of a bifurcated chalcogen bond were confirmed by NCIplot analysis of 13 , which showed the presence of two reduced density gradient disk shape green isosurfaces (Figure g).…”

Chalkogenbindungs‐induzierte Doppelhelix basierend auf der Selbstassemblierung eines kleinen planaren Bausteins

“…Wir haben bereits Erfahrung mit der Synthese von Benzotellurazolen und der Untersuchung von Chalkogenbindungen, die von diesen Bausteinen gebildet werden. [27,54] So konnte gezeigt werden, dass die Tellurzentren von Benzotellurazolen starke Wechselwirkungen sowohl mit Stickstoffzentren als auch mit Sauerstoffatomen von Carbonylgruppen eingehen können, was zu supramolekularen Strukturen im Festkörper führen kann. [27,54,55] Unser Konzept bestand nun darin, Benzotellurazolamide als Bausteine zu verwenden (siehe Abbildung 1).…”

“…[27,54] So konnte gezeigt werden, dass die Tellurzentren von Benzotellurazolen starke Wechselwirkungen sowohl mit Stickstoffzentren als auch mit Sauerstoffatomen von Carbonylgruppen eingehen können, was zu supramolekularen Strukturen im Festkörper führen kann. [27,54,55] Unser Konzept bestand nun darin, Benzotellurazolamide als Bausteine zu verwenden (siehe Abbildung 1). Sie besitzen Te-Zentren als Chalkogenbindungsdonoren sowie C=O-Gruppen und N-Atome als Chalkogenbindungsakzeptoren (Abbildung 1a).…”