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Discriminating Halogen‐Bonding from Other Noncovalent Interactions by a Combined NOE NMR/DFT Approach
Author(s) -
Ciancaleoni Gianluca,
Bertani Roberta,
Rocchigiani Luca,
Sgarbossa Paolo,
Zuccaccia Cristiano,
Macchioni Alceo
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201404883
Subject(s) - dabco , chemistry , adduct , halogen bond , non covalent interactions , octane , iodide , nuclear magnetic resonance spectroscopy , halogen , lewis acids and bases , lone pair , hsab theory , crystallography , ab initio , computational chemistry , hydrogen bond , stereochemistry , molecule , alkyl , organic chemistry , catalysis
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 ( Me 3 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 Me 3 Py / I1 and Me 3 Py / I2 , and 44 % for DABCO / Br.