Influence of Substituents in the Benzene Ring on the Halogen Bond of Iodobenzene with Ammonia

Abstract

The effects on the CÀ I••N halogen bond between iodobenzene and NH 3 of placing various substituents on the phenyl ring are monitored by quantum calculations. Substituents R = N(CH 3 ) 2 , NH 2 , CH 3 , OCH 3 , COCH 3 , Cl, F, COH, CN, and NO 2 were each placed ortho, meta, and para to the I. The depth of the σ-hole on I is deepened as R becomes more electron-withdrawing which is reflected in a strengthening of the halogen bond, which varied between 3.3 and 5.5 kcal mol À 1 . In most cases, the ortho placement yields the largest perturbation, followed by meta and then para, but this trend is not universal. Parallel to these substituent effects is a progressive lengthening of the covalent CÀ I bond. Formation of the halogen bond reduces the NMR chemical shielding of all three nuclei directly involved in the CÀ I••N interaction. The deshielding of the electron donor N is most closely correlated with the strength of the bond, as is the coupling constant between I and N, so both have potential use as spectroscopic measures of halogen bond strength.

Large31P-NMR enhancements in liquid state dynamic nuclear polarization through radical/target molecule non-covalent interaction

“…33 The values were corrected for the basis set superposition error with the Boys-Bernardi procedure (ESI †). [34][35][36][37] The calculations were performed in vacuum as well as with the implicit solvation model C-PCM 38,39 for benzene and chloroform, using the same starting geometries. We calculated the isotropic hyperfine coupling to 31 P using EPR-III basis set 40 for H, C, N, and O atoms and IGLO-II 41 for P atom.…”

Adjusting the balance between hydrogen and chalcogen bonds

“…Numerous past calculations of related systems have confirmed the dependability and accuracy of this combined approach. 15,58,67,71,[76][77][78][79][80][81][82] The aug-cc-pVDZ-PP pseudopotential 83 was applied to fourth-row Te as it takes into account certain relativistic effects. The larger triple-z aug-cc-pVTZ set was used to compute specialized electronic parameters, such as charge transfers, NBO, and AIM properties, along with the all-electron cc-pVTZ-DK3 basis for Te.…”

Substituent Effect and Its Halogen‐Atom Dependence of Halogen Bonding Viewed through Electron Density Changes

“…Detailed control of intermolecular interactions is an important factor for finely‐tuned design of functionally important molecules. With regard to halogen bonding, a practical way to realize it would be to utilize the substituent effect [22,34–40] . It is widely recognized that substitution with an electron‐withdrawing group (such as a fluorine atom) on the benzene ring of an aromatic halogenated molecule gives rise to enhancement of halogen‐bond strength.…”