Elucidating the Binding Mode of Sulfur- and Selenium-Based Cationic Chalcogen-Bond Donors

For a comparison of the interaction modes of various chalcogen-bond donors, 2-chalcogeno-imidazolium salts have been designed, synthesized, and studied by single crystal X-ray diffraction, solution NMR and DFT as well as for their ability to act as activators in an SN1-type substitution reaction. Their interaction modes in solution were elucidated based on NMR diffusion and chemical shift perturbation experiments, which were supported by DFT-calculations. Our finding is that going from lighter to the heavier chalcogens, hydrogen bonding plays a less, while chalcogen bonding an increasingly important role for the coordination of anions. Anion-π interactions also show importance, especially for the sulfur and selenium derivatives.

Open-Cage Fullerene as Molecular Container for F- , Cl- , Br- and I. Angew Chem Int Ed Engl 2022;61:e202212090. [PMID: 36316627 DOI: 10.1002/anie.202212090]

A 19-membered open-cage fullerene derivative was prepared from C₆₀ in 7 steps and 5.5 % yield through the peroxide-mediate pathway. There are four carbonyl groups, an ether oxygen and a quinoxaline moiety on the rim of the orifice. A chloride anion could be inserted into its cavity by heating with hydrochloric acid at 60 °C for 4 h. Encapsulation of fluoride, bromide and iodide anions was also achieved at slightly more forcing conditions, 90 °C for 14 h. Single crystal X-ray structures of the sodium salt of the chloride and the bromide encapsulated derivatives were obtained, which showed the halide anion in the center of the cavity and two sodium cations connecting two cages through coordination to the oxygen atoms on the rim of the orifices. The halide encapsulation ratio is quantitative in the isolated products.