Acceptor number of halogenated solvents and its potential as a criterion for the ability of halogen bonding as a specific solvent effect using the 31P NMR chemical shift of triethylphosphine oxide as a probe

Acceptor numbers (AN) of several halogenated and perfluorohalogenated solvents were determined using 31P NMR of triethylphosphine oxide (Et3PO) as a probe. The halogen and/or hydrogen bonding complex, C–X⋯OPEt3 or C–H⋯OPEt3, between the probe and solvent molecules was simulated by MP2 and DFT methods. The halogen bonding energies of perfluorohalogenated solvents and iodobenzene with the probe show a good linear correlation to the AN. The results indicate that the AN can act as a possible criterion for the ability of halogen bonding as a specific solvent effect.