Phosphine Oxides as Spectroscopic Halogen Bond Descriptors: IR and NMR Correlations with Interatomic Distances and Complexation Energy

Abstract

An extensive series of 128 halogen-bonded complexes formed by trimethylphosphine oxide and various F-, Cl-, Br-, I- and At-containing molecules, ranging in energy from 0 to 124 kJ/mol, is studied by DFT calculations in vacuum. The results reveal correlations between R–X⋅⋅⋅O=PMe3 halogen bond energy ΔE, X⋅⋅⋅O distance r, halogen’s σ-hole size, QTAIM parameters at halogen bond critical point and changes of spectroscopic parameters of phosphine oxide upon complexation, such as 31P NMR chemical shift, ΔδP, and P=O stretching frequency, Δν. Some of the correlations are halogen-specific, i.e., different for F, Cl, Br, I and At, such as ΔE(r), while others are general, i.e., fulfilled for the whole set of complexes at once, such as ΔE(ΔδP). The proposed correlations could be used to estimate the halogen bond properties in disordered media (liquids, solutions, polymers, glasses) from the corresponding NMR and IR spectra.

Modeling of Solute-Solvent Interactions Using an External Electric Field—From Tautomeric Equilibrium in Nonpolar Solvents to the Dissociation of Alkali Metal Halides

“…Noncovalent interactions allow our world to exist. Their specific interaction energies [ 1 , 2 , 3 , 4 ], their effect on the spectral [ 5 , 6 , 7 ], chemical [ 8 , 9 ], and structural [ 10 , 11 , 12 ] properties of individual molecules, those in adducts and solutions [ 13 , 14 , 15 ], have been and remain vital to the progress of chemistry. The interpretation of spectral shifts caused by changes in the properties of a particular interaction can be carried out in sufficient detail [ 16 ].…”

Study of interactions between Brønsted acids and triethylphosphine oxide in solution by 31P NMR: evidence for 2 : 1 species

“…2 Since then, this method has been employed to characterize liquids with acidic properties, such as boron compounds used as Lewis acid catalysts, 3 and different types of ionic liquids with Brønsted 4 or Lewis 5,6 acidity, and phosphine oxides have been proposed as descriptors for halogen bonds. 7 A similar methodology, taking the chemical shift at infinite dilution, has been applied for the determination of acidity by 13 C NMR using mesityl oxide as the probe molecule. 8 The 31 P NMR method with TEPO was soon adapted for the characterization of solids, creating a scale of global acidity.…”

Challenging the electrostatic σ‐hole picture of halogen bonding using minimal models and the interacting quantum atoms approach

“…[64][65][66] We have chosen this functional according to our previous experience and its successful performance in a number of halogen bond studies in various similar supramolecular systems. [67][68][69][70][71] In order to avoid problems with relativistic effects, we used the specially developed segmented contracted all-electron relativistic basis sets x2c-TZVPPall and the Ahlrich's family basis sets def2-TZVPP with all-electron spin-free X2C correction for iodine. 72 We have also previous experience on the successful application of such basis sets in studies of NCIs 73,74 and, in particular, in chemical systems containing heavy atoms (noble metals, iodine).…”