Probing halogen bonds with solid-state NMR spectroscopy: observation and interpretation of J(⁷⁷Se,³¹P) coupling in halogen-bonded PSe⋯I motifs

Abstract

Intra-halogen bond J couplings measured via NMR spectroscopy and interpreted using natural localized molecular orbitals offer novel insights into this class of non-covalent interaction.

Rapid Identification of Halogen Bonds in Co‐Crystalline Powders via 127I Nuclear Quadrupole Resonance Spectroscopy

“…[51] The changes represent increases of 0.4 %t o1 .6 %f or 35 Cl, 2.3 % to 3.8 %f or 79/81 Br, and 2.9 %t o4 .0 %f or 127 I. Each nucleus has au nique Sternheimer antishielding factor [57,58] and quadrupole moment (Q[ 127 I] = À617 mb; Q[ 79 Br] = 308.7(2) mb); Q[ 81 Br] = 257.9(2) mb; Q[ 35 Cl] = À81.12 mb), [59] with the latter taken into account using Equation (1) and solving for V 33 .The substantial shifts in the resonance frequencies as ar esult of halogen bonding far exceed the possible variation due to temperature fluctuations.…”

“…It has been shown that the CÀIb ond stretches upon halogen bonding,w ith the resulting changes in the vibrational frequencies being good identifiers of halogenbonded complexes. [30,33] Consequently,t he value of C Q ( 127 I) correlates with both the CÀIc ovalent-bond length and the halogen-bond distance. [30,33] Consequently,t he value of C Q ( 127 I) correlates with both the CÀIc ovalent-bond length and the halogen-bond distance.…”

“…[23] Despite its widespread usage as asupramolecular and crystal-engineering tool, the nature of the halogen bond continues to be debated in the literature. [24][25][26][27] Solid-state nuclear magnetic resonance (SSNMR) spectroscopy has been shown to be apowerful tool to characterize halogen-bonded adducts, [28,29] offering information on chemical shifts, [30,31] J-couplings, [32,33] dipolar coupling, [34] and quadrupolar coupling. [35][36][37][38] As ac rystal-engineering tool, 13 C chemical shifts were shown to be sensitive to the occurrence of ah alogen bond, [30,31] while the I···N halogen bond length has been measured using 15 N-127 Id ipolar coupling.…”

Solid-State NMR at the University of Ottawa

“…8). 29 Computed J( 77 Se, 31 P) values improve relative to experiment when the iodinated halogen bond acceptor is included in the structural model. Natural localized molecular orbital (NLMO) calculations indicate that contributions from the selenium lone pair orbital dominate both the magnitude and the observed trend in the coupling constants.…”

“…The method we have developed, inspired by Darren Brouwer's approach to solving zeolite structures using 29 Si (spin-1/2) NMR data, 21 begins with a structural model obtained from either a powder X-ray pattern or an ab initio approach. The model is refined successively against the experimental quadrupolar coupling data by evaluating the agreement between these data and those computed on the basis of the current structural iteration.…”