⁷⁷Se and ¹²⁵Te solid-state NMR and X-ray diffraction structural study of chalcogen-bonded 3,4-dicyano-1,2,5-chalcogenodiazole cocrystals

Abstract

Three novel chalcogen-bonded cocrystals featuring 3,4-dicyano-1,2,5-selenodiazole (C4N4Se) or 3,4-dicyano-1,2,5-tellurodiazole (C4N4Te) as chalcogen-bond donors and hydroquinone (C6H6O2), tetraphenylphosphonium chloride (C24H20P+·Cl−) or tetraethylphosphonium chloride (C8H20P+·Cl−) as chalcogen-bond acceptors have been prepared and characterized by single-crystal X-ray diffraction (XRD), powder X-ray diffraction and 77Se/125Te magic-angle spinning solid-state NMR spectroscopy. The single-crystal XRD results show that the chalcogenodiazole molecules interact with the electron donors through two σ-holes on each of the chalcogen atoms, which results in highly directional and moderately strong chalcogen bonds. Powder XRD confirms that the crystalline phases are preserved upon moderate grinding of the samples for solid-state NMR experiments. Measurement of 77Se and 125Te chemical shift tensors via magic-angle spinning solid-state NMR spectroscopy confirms the number of magnetically unique chalcogen sites in each asymmetric unit and reveals the impact of chalcogen-bond formation on the local electronic structure. These NMR data are further assessed in the context of analogous data for a wider range of crystalline chalcogen-bonded systems.

Unraveling Sodium-Ion Dynamics in Honeycomb-Layered Na2MgxZn2–xTeO6 Solid Electrolytes with Solid-State NMR

“…= 7.07%) is the preferred isotope over 123 Te (γ = −7.06 × 10 7 rad s –1 T –1 ; Ξ = 26.17%, N.A. = 0.89%) due to its higher natural abundance and frequency ratio, and yields sharp NMR line shapes with excellent resolution over a large chemical shift window of ∼5000 ppm that is sensitive to different electronic structures and Te oxidation states in various organo- and inorganic tellurium compounds. − …”

Competition between Binding to Various Sites of Substituted Imidazoliums

“…It has been understood for some time that the formation of an HB induces changes in the chemical shielding of not only the bridging proton but also neighboring atoms such as the atom bonded to H and the electron-donating base atom. More recent work has documented evidence that the formation of other noncovalent bonds that are closely related to HBs, such as halogen and chalcogen bonds, also induces clear shifts in the NMR signal of the atoms involved. − Of this set of atoms, the one that appears to bear the closest correlation with the strength of the bond is the electron donor atom, ,, which in this case would be the N of NH 3 .…”

Competition Between the Two σ‐Holes in the Formation of a Chalcogen Bond

“…[36] The ChB runs a full spectrum of bond strength [40] with Te being particularly strong, [41] and reveals itself in a number of ways including solid state NMR. [42,43] A good deal of our present understanding of the ChB is contained in a number of recent review articles [24,[44][45][46][47][48] to which an interested reader is referred.…”

“…Continuing research has revealed the occurrence of these bonds in biomolecules such as proteins and nucleic acids [21,35–39] or SAM riboswitches [36] . The ChB runs a full spectrum of bond strength [40] with Te being particularly strong, [41] and reveals itself in a number of ways including solid state NMR [42,43] . A good deal of our present understanding of the ChB is contained in a number of recent review articles [24,44–48] to which an interested reader is referred.…”