From Noncovalent Chalcogen–Chalcogen Interactions to Supramolecular Aggregates: Experiments and Calculations

Abstract

This review considers noncovalent bonds between divalent chalcogen centers. In the first part we present X-ray data taken from the solid state structures of dimethyl- and diphenyl-dichalcogenides as well as oligoalkynes kept by alkyl-sulfur, -selenium, and -tellurium groups. Furthermore, we analyzed the solid state structures of medium sized (12-24 ring size) selenium coronands and medium to large rings with alkyne and alkene units between two chalcogen centers. The crystal structures of the cyclic structures revealed columnar stacks with close contacts between neighboring rings via noncovalent interactions between the chalcogen centers. To get larger space within the cavities, rings with diyne units between the chalcogen centers were used. These molecules showed channel-like structures in the solid state. The flexibility of the rings permits inclusion of guest molecules such as five-membered heterocycles and aromatic six-membered rings. In the second part we discuss the results of quantum chemical calculations. To treat properly the noncovalent bonding between chalcogens, we use diffuse augmented split valence basis sets in combination with electron correlation methods. Our model substances were 16 dimers consisting of two Me-X-Me (X = O, S, Se, Te) pairs and dimers of Me-X-Me/Me-X-CN (X = O, S, Se, Te) pairs. The calculations show the anticipated increase of the interaction energy from (Me-O-Me) (-2.15 kcal/mol) to (Me-O-Me/Me-Te-CN) (-6.59 kcal/mol). An analysis by the NBO method reveals that in the case of the chalcogen centers O and S the hydrogen bridges between the molecules dominate. However, in the case of Se and Te the major bonding between the pairs originates from dispersion forces between the chalcogen centers. It varies between -1.7 and -4.0 kcal/mol.

Unveiling the Sulfur–Sulfur Bridge: Accurate Structural and Energetic Characterization of a Homochalcogen Intermolecular Bond

“…In parallel, non-covalent chalcogen-bond interactions have attracted much attention because of the fundamental role they play in different fields such as catalysis, [8] drug design, [1] self-assembly processes, [9] and crystal packing. [10] Understanding the mechanisms at the basis of these technological processes requires the characterization of the directionality,strength, and nature of such interactions [11] as well as acomprehensive analysis of their competition with other noncovalent bonds,a lso taking into account the tuning of these properties by different environments.I nt his respect, in analogy to the halogen bond [12] the sulfur atom can act either as achalcogen bond donor (due to a s- [13,14] or p-hole [13,15] on sulfur) or as acceptor (because of al one-pair on sulfur, as in thioethers [14] ).…”

N‐Aryl Imidazole Platforms – Synthesis and Structural Investigation

“…This orientation and the large distances between the bromine atoms make these chiral N-aryl imidazole platforms to promising candidates for applications in supramolecular chemistry; especially, they should be suitable for the design of supramolecular receptors that have recognition units based on halogen [37] and chalcogen [38] bonds. Relative to the synthesis of the related chiral N-methyl imidazole amino acids, harsher reaction conditions are needed.…”

Chalcogen‐Bonding Catalysis: From Neutral to Cationic Benzodiselenazole Scaffolds

“…The large, polarizable, almost directionless π surface offered by anion‐ π interactions appears ideal to stabilize anionic transition states that involve charge displacements over longer distances, e.g ., cascade cyclizations . The advantages of σ ‐hole interactions, the unorthodox counterpart of hydrogen bonds, appear almost complementary: More hydrophobic and directional than hydrogen bonds, they should be ideal for high‐precision catalysis in apolar media.…”

“…Originating from anti‐bonding σ * orbitals, chalcogen bonds extend linearly from the covalent bonds (bond angle Φ 1 ~ 180°) and thus appear on the side of the chalcogen atom (bond angle Φ 2 ~ 70°, Figure ,a ) . They have been studied extensively in crystal engineering and for intramolecular conformational control in solution, including prominent use in medicinal chemistry and pioneering applications in covalent catalysis . The use of intermolecular chalcogen bonds in functional systems in solution is rare and recent, non‐covalent chalcogen‐bonding catalysis has been introduced only last year.…”