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Group 16 chalcogen atoms may exhibit Lewis acidic σ-holes which are able to form attractive supramolecular interactions with Lewis bases via chalcogen bonds (ChB). Interest in ChB is increasing rapidly; however, the potential for anion binding has not been fully explored. Herein we report on the application of chemically robust and stable benzylic selenocynates (1 and 2) for halide ion recognition in the solid state and in solution. Single crystal X-ray structural analysis of various cocrystals reveals structurally important Se…X− (X = Cl, Br, I) chalcogen bonds. Changes in the 13C and 77Se chemical shifts via NMR spectroscopy show how halide ion recognition influences the local electronic environment of the selenium atoms in solution. Deviations of the interaction from the extension of the C–Se covalent bond are quantified and assessed with the aid of computational chemistry. [ABSTRACT FROM AUTHOR]

An overview of the role of solid-state nuclear magnetic resonance (SSNMR) spectroscopy in the field of crystal engineering is provided. NMR methodologies often provide insights into the structure and dynamics of solid materials which would otherwise be unavailable by X-ray diffraction. More generally, NMR crystallographic structure solutions or refinement approaches seek to incorporate available data from all sources, including the results of density functional theory calculations and diffraction data. This Highlight article discusses the state of the field through a recapitulation of relevant theory and selected applications from the literature. Specific topics covered include NMR structure refinement, polymorph identification and differentiation, non-covalent interactions, and the role of dynamics. [ABSTRACT FROM AUTHOR]

Halogen bonds constitute an important and topical class of non-covalent interaction. We report a combined X-ray diffraction, multinuclear (77Se, 31P, 13C) solid-state magnetic resonance, and computational study of a series of crystalline triphenylphosphine selenide-iodoperfluorobenzene complexes which feature P=Se⋯I-C halogen bonds. Selenium-77 chemical shifts increase due to halogen bonding with iodine and correlate with the P=Se distance, which in turn correlates with the strength of the halogen bond. (77Se, 31P) coupling constants increase in magnitude as the halogen bond weakens. This observation is understood a natural localized molecular orbital (NLMO) DFT approach which shows that contributions from the selenium lone pair orbital tend to dominate both the magnitude and trends in (77Se, 31P), with the selenium-phosphorus bonding orbital being the second largest contributor. This work suggests that couplings measured NMR spectroscopy may play an important role in the characterization of halogen bonds, in clear analogy with their role in the characterization of hydrogen bonds. [ABSTRACT FROM AUTHOR]

Reaction of 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (TPymT) with Pb(NO3)2 in aqueous medium leads to the formation of a mixture of two pseudopolymorphs, {[Pb2(TPymT)(H2O)(NO3)4]·H2O}n, 1 and [Pb2(TPymT)(NO3)4]n, 2, where TPymT molecules are coordinated with two PbII ions in a bridging bis-terpyridine fashion. We demonstrate that fast evaporation of the solvent leads exclusively to the formation of 1, while 2 was formed upon slow evaporation. The two pseudopolymorphs can be interconverted by dissolving in water upon heating and controlling the evaporation rate. [ABSTRACT FROM AUTHOR]

The crystal structures of two sodium diphosphates (Na4P2O7 and Na3HP2O7·H2O) that were solved using diffraction methods are refined with the use of 23Na and 31P NMR data in conjunction with projector-augmented-wave density functional theory (DFT) calculations. The sodium cations' NMR parameters are shown to be particularly well suited for the investigation of crystalline structures as they are largely dictated by the crystalline network instead of local directional bonding interactions. High-resolution spin-diffusion 23Na correlation spectra were acquired with the use of double rotation (DOR) and the spin diffusion build-up curves were modeled with the use of the rate matrix method. The availability of dipolar-based information from these measurements is important in validating the assignment of the resonances prior to performing structural refinements using the 23Na EFG tensor parameters. The NMR-refined structures of Na4P2O7 and Na3HP2O7·H2O are then cross-validated with the use of diffraction and magnetic shielding tensor information and are compared to the pure DFT and X-ray diffraction structures. A new crystal structure of Na3HP2O7·9H2O is solved using single-crystal X-ray diffraction and is compared to the refined crystal structures of Na3HP2O7·H2O. The combination of methods used in this work ensures consistency of the final structures with all available data. [ABSTRACT FROM AUTHOR]

Reaction of 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (TPymT) with Pb(NO3)2 in aqueous medium leads to the formation of a mixture of two pseudopolymorphs, {[Pb2(TPymT)(H2O)(NO3)4]·H2O}n, 1 and [Pb2(TPymT)(NO3)4]n, 2, where TPymT molecules are coordinated with two PbII ions in a bridging bis-terpyridine fashion. We demonstrate that fast evaporation of the solvent leads exclusively to the formation of 1, while 2 was formed upon slow evaporation. The two pseudopolymorphs can be interconverted by dissolving in water upon heating and controlling the evaporation rate. [ABSTRACT FROM AUTHOR]