title: Discriminating halogen-bonding from other noncovalent interactions by a combined NOE NMR/DFT approach.
abstract: Herein a combined NOE NMR/DFT methodology to discriminate between adducts held together by halogen bonding (XB) and other noncovalent interactions (non-XB, such as lone pair/π), based on the determination of the XB donors' and acceptors' relative orientation, is proposed. In particular, (19) F,(1) H HOESY NMR spectroscopy experiments and DFT calculations on different XB donors, such as perfluorohexyl iodide (I1), iodopentafluorobenzene (I2) and bromopentafluorobenzene (Br), combined with different Lewis bases, such as 1,4-diazabicyclo[2.2.2]octane (DABCO) and 2,4,6-trimethylpyridine (Me3 Py), were performed. The results clearly show that in the case DABCO/I1 the XB adduct is practically the only one present in solution, whereas for the other pairs a certain amount of non-XB adduct is present. Combining DFT and HOESY results, the amount of non-XB adducts can be roughly quantified under our experimental conditions as 4 % for DABCO/I2, between 10 and 20 % for Me3 Py/I1 and Me3 Py/I2, and 44 % for DABCO/Br.
authors.affiliation: Istituto di Scienze e Tecnologie Molecolari del CNR (CNR-ISTM) c/o Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Via Elce di Sotto 8, 06123, Perugia (Italy). gciancaleoni@gmail.com.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Ciancaleoni
authors.forename: Roberta
authors.initials: R
authors.lastname: Bertani
authors.forename: Luca
authors.initials: L
authors.lastname: Rocchigiani
authors.forename: Paolo
authors.initials: P
authors.lastname: Sgarbossa
authors.forename: Cristiano
authors.initials: C
authors.lastname: Zuccaccia
authors.forename: Alceo
authors.initials: A
authors.lastname: Macchioni
keywords: NMR spectroscopy; density functional calculations; halogens; noncovalent interactions