6533b7d2fe1ef96bd125ecfa
RESEARCH PRODUCT
Substituent Effects on the [N-I-N](+) Halogen Bond
Rakesh PuttreddyKari RissanenAnna-carin C. CarlssonMichele BedinAlavi KarimBijan NekoueishahrakiAlexei A. NeverovJürgen GräfensteinMartin UhrbomKrenare MehmetiMáté ErdélyiRoland Kleinmaiersubject
inorganic chemicalsElectron densityPopulationInorganic chemistryhalogen bondsSubstituent010402 general chemistry01 natural sciencesBiochemistryCatalysisArticlechemistry.chemical_compoundColloid and Surface ChemistryPyridineeducationBenzeneta116education.field_of_studyHalogen bond010405 organic chemistryChemical shiftGeneral ChemistryKemi0104 chemical sciencesCrystallographychemistryChemical SciencesPolar effectdescription
We have investigated the influence of electron density on the three-center [N-I-N](+) halogen bond. A series of [bis(pyri din e) io dine](+) and [1,2-bis ( (pyridin e-2-71 ethynyl)b e nze n e)io dine](+) BF4- complexes substituted with electron withdrawing and donating functionalities in the para-position of their pyridine nitrogen were synthesized and studied by spectroscopic and computational methods. The systematic change of electron density of the pyridine nitrogens upon alteration of the para-substituent (NO2, CF3, H, F, Me, OMe, NMe2) was confirmed by N-15 NMR and by computation of the natural atomic population and the pi electron population of the nitrogen atoms. Formation of the [N-I-N](+) halogen bond resulted in >100 ppm N-15 NMR coordination shifts. Substituent effects on the N-15 NMR chemical shift are governed by the pi population rather than the total electron population at the nitrogens. Isotopic perturbation of equilibrium NMR studies along with computation on the DFT level indicate that all studied systems possess static, symmetric [N-I-N](+) halogen bonds, independent of their electron density. This was further confirmed by single crystal X-ray diffraction data of 4-substituted [bis(pyridine)iodine](+) complexes. An increased electron density of the halogen bond acceptor stabilizes the [N center dot center dot center dot I center dot center dot center dot N](+) bond, whereas electron deficiency reduces the stability of the complexes, as demonstrated by UV-kinetics and computation. In contrast, the N-I bond length is virtually unaffected by changes of the electron density. The understanding of electronic effects on the [N-X-N](+) halogen bond is expected to provide a useful handle for the modulation of the reactivity of [bis(pyridine)halogen](+)-type synthetic reagents.
year | journal | country | edition | language |
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2016-06-07 |