title: Tuning the halogen/hydrogen bond competition: a spectroscopic and conceptual DFT study of some model complexes involving CHF2I.
abstract: Insight into the key factors driving the competition of halogen and hydrogen bonds is obtained by studying the affinity of the Lewis bases trimethylamine (TMA), dimethyl ether (DME), and methyl fluoride (MF) towards difluoroiodomethane (CHF(2) I). Analysis of the infrared and Raman spectra of solutions in liquid krypton containing mixtures of TMA and CHF(2) I and of DME and CHF(2) I reveals that for these Lewis bases hydrogen and halogen-bonded complexes appear simultaneously. In contrast, only a hydrogen-bonded complex is formed for the mixtures of CHF(2) I and MF. The complexation enthalpies for the C-H⋅⋅⋅Y hydrogen-bonded complexes with TMA, DME, and MF are determined to be -14.7(2), -10.5(5) and -5.1(6) kJ mol(-1), respectively. The values for the C-I⋅⋅⋅Y halogen-bonded isomers are -19.0(3) kJ mol(-1) for TMA and -9.9(8) kJ mol(-1) for DME. Generalization of the observed trends suggests that, at least for the bases studied here, softer Lewis bases such as TMA favor halogen bonding, whereas harder bases such as MF show a substantial preference for hydrogen bonding.
authors.affiliation: Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium).
authors.forename: Nick
authors.initials: N
authors.lastname: Nagels
authors.forename: Yannick
authors.initials: Y
authors.lastname: Geboes
authors.forename: Balazs
authors.initials: B
authors.lastname: Pinter
authors.forename: Frank
authors.initials: F
authors.lastname: De Proft
authors.forename: Wouter A
authors.initials: WA
authors.lastname: Herrebout
mesh_terms: D006219:Halogens / Q000737:chemistry*; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D006847:Hydrocarbons, Iodinated / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D058115:Lewis Bases / Q000737:chemistry; D008738:Methyl Ethers / Q000737:chemistry; D008744:Methylamines / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D006219:Halogens; D006845:Hydrocarbons, Fluorinated; D006847:Hydrocarbons, Iodinated; D058115:Lewis Bases; D008738:Methyl Ethers; D008744:Methylamines; C029999:fluoromethane; D006859:Hydrogen; C033413:dimethyl ether; C023336:trimethylamine
keywords: Lewis bases; density functional calculations; hydrogen bonding; non-covalent interactions; vibrational spectroscopy