Speaker
Description
In hydrogen bonding, heavy halogen atoms typically act as acceptors due to high polarizability and moderate electronegativity. By contrast, the situation in halogen bonds is fundamentally different. Here, halogen atoms act as donors due to local electron depletion caused by highly electronegative substituents combined with good polarizability of the halogen atom. This results in the formation of a so called σ-hole, which is an area of positive electrostatic potential. Consequently, there is an inverse correlation between good hydrogen bond donors and good halogen bond donors with respect to electron density. [1]
Although there exists some experimental work on halogen bonds using microwave spectroscopy, only a few donor-acceptor combinations have been studied thus far. [1] We have chosen to conduct a systematic study of the substitution patterns of fluoroiodobenzenes in combination with the prominent acceptor pyridine, employing cavity Fourier transform microwave jet spectroscopy. The electric field gradient of the iodine atoms was used as a probe, enabling the quantification of the mesomeric and inductive effects from the fluorine substituents by application of the extended Townes-Dailey model [2,3] combined with intrinsic basis bonding analysis [4] and other theoretical methods. This provides insights into how the strength of the halogen bond donor or hydrogen bond acceptor is affected and therefore how the equilibrium between hydrogen and halogen bonds in iodine-containing systems can be controlled by different substitution patterns.
[1] G. Cavallo et al., Chem. Rev. 2016, 116, 478–2601.
[2] B.P. Dailey et al., J. Chem. Phys. 1955, 23, 118–123.
[3] S. E. Novick, J. Mol. Spectrosc., 2011, 267, 13–18.
[4] G. Knizia, J. Chem. Theory Comput., 2013, 9, 4834–4843.
| Keywords | Hydrogen bond: medium; State of system: gas; Halogen bond. |
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| This abstract is submitted for.... | Early-career researchers´ workshop |
