title: Natural Abundance15N and13C Solid-State NMR Chemical Shifts: High Sensitivity Probes of the Halogen Bond Geometry.
abstract: Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is a versatile characterization technique that can provide a plethora of information complementary to single crystal X-ray diffraction (SCXRD) analysis. Herein, we present an experimental and computational investigation of the relationship between the geometry of a halogen bond (XB) and the SSNMR chemical shifts of the non-quadrupolar nuclei either directly involved in the interaction (15N) or covalently bonded to the halogen atom (13C). We have prepared two series of X-bonded co-crystals based upon two different dipyridyl modules, and several halobenzenes and diiodoalkanes, as XB-donors. SCXRD structures of three novel co-crystals between 1,2-bis(4-pyridyl)ethane, and 1,4-diiodobenzene, 1,6-diiodododecafluorohexane, and 1,8-diiodohexadecafluorooctane were obtained. For the first time, the change in the15N SSNMR chemical shifts upon XB formation is shown to experimentally correlate with the normalized distance parameter of the XB. The same overall trend is confirmed by density functional theory (DFT) calculations of the chemical shifts.13C NQS experiments show a positive, linear correlation between the chemical shifts and the C-I elongation, which is an indirect probe of the strength of the XB. These correlations can be of general utility to estimate the strength of the XB occurring in diverse adducts by using affordable SSNMR analysis.
authors.affiliation: Department of Chemistry and NIS centre, University of Torino, Via P. Giuria 7, 10125, Torino, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Cerreia Vioglio
authors.affiliation: NFMLab-D.C.M.I.C. "Giulio Natta", Politecnico di Milano, Via L. Mancinelli 7, 20131, Milano, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Catalano
authors.affiliation: NFMLab-D.C.M.I.C. "Giulio Natta", Politecnico di Milano, Via L. Mancinelli 7, 20131, Milano, Italy.
authors.forename: Vera
authors.initials: V
authors.lastname: Vasylyeva
authors.affiliation: Department of Chemistry and NIS centre, University of Torino, Via P. Giuria 7, 10125, Torino, Italy.
authors.forename: Carlo
authors.identifier: http://orcid.org/0000-0002-3712-7369
authors.initials: C
authors.lastname: Nervi
authors.affiliation: Department of Chemistry and NIS centre, University of Torino, Via P. Giuria 7, 10125, Torino, Italy.
authors.forename: Michele R
authors.identifier: http://orcid.org/0000-0002-8734-6009
authors.initials: MR
authors.lastname: Chierotti
authors.affiliation: NFMLab-D.C.M.I.C. "Giulio Natta", Politecnico di Milano, Via L. Mancinelli 7, 20131, Milano, Italy.
authors.forename: Giuseppe
authors.identifier: http://orcid.org/0000-0002-0797-9296
authors.initials: G
authors.lastname: Resnati
authors.affiliation: Department of Chemistry and NIS centre, University of Torino, Via P. Giuria 7, 10125, Torino, Italy.
authors.forename: Roberto
authors.identifier: http://orcid.org/0000-0002-2431-8051
authors.initials: R
authors.lastname: Gobetto
authors.affiliation: NFMLab-D.C.M.I.C. "Giulio Natta", Politecnico di Milano, Via L. Mancinelli 7, 20131, Milano, Italy.|VTT-Technical Research Centre of Finland, Biologinkuja 7, 02150, Espoo, Finland.
authors.forename: Pierangelo
authors.identifier: http://orcid.org/0000-0002-7945-099X
authors.initials: P
authors.lastname: Metrangolo
keywords: CPMAS; NMR spectroscopy; chemical shifts; halogen bonding; normalized distance parameter