Abstract
As halogen bonding is a weak, transient interaction, its description in solution is challenging. We demonstrate that scalar coupling constants (J) are modulated by halogen bonding. The binding-induced magnitude change of one-bond couplings, even up to five bonds from the interaction site, correlates to the interaction strength. We demonstrate this using the NMR data of 42 halogen-bonded complexes in dichloromethane solution and by quantum chemical calculations. Our observation puts scalar couplings into the toolbox of methods for characterization of halogen bond complexes in solution and paves the way for their applicability for other types of weak σ-hole interactions.
Highlights
The halogen bond (XB) is a net attractive interaction of a polarized halogen and a Lewis base.[1]
The use of fluorinated halogen bond donors in combination with nonfluorinated Lewis bases diminishes the risk of signal overlaps, which is further supported by the wide, ∼800 ppm, chemical shift scale of
Scalar coupling constants are demonstrated to reflect the strength of halogen bonds in solution
Summary
The halogen bond (XB) is a net attractive interaction of a polarized halogen and a Lewis base.[1]. Besides UV, IR, and ITC studies, complexation-induced NMR chemical shift alterations have typically been used for the characterization of halogen-bonded complexes.[14] NMR is often preferred, as it tolerates high concentrations that are necessary to study weak interactions in solution and as it provides detailed structural information.[15] Whereas coupling constants are widely utilized in the elucidation of conformational states, their potential for the detection of halogen bonding in solution has not yet been experimentally evaluated. Recent observation of the geometry and bond strength dependence of the 1JCh,P of P Ch···I-type complexes (where Ch denotes a chalcogen) in the solid state[16−18] and computational reports on throughbond couplings in exotic systems[19,20] implicate that scalar couplings ought to be applicable for the characterization of weak interactions
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