Influence of Substituents in the Aromatic Ring on the Strength of Halogen Bonding in Iodobenzene Derivatives
Maria V. Chernysheva, Margarita Bulatova, Xin Ding, Matti Haukka
Abstract
The halogen-bonding properties of 3,4,5-triiodobenzoic acid (1, 2), 1,2,3-triiodobenzene (3), 4-iodobenzoic acid (4), pentaiodobenzoic acid ethanol solvate (5), hexaiodobenzene (6a–c), 4-iodobenzonitrile (7), 3-iodobenzonitrile (8), 2,4-diiodoaniline (9), 4-iodoaniline (10), 2-iodoaniline (11), 2-iodophenol (12), 4-iodophenol (13), 3-iodophenol (14), 2,4,6-triiodophenol (15), 4-iodoanisole (16), and 3,4,5-triiodoanisole (17) have been studied. The results suggested that substituents other than halogen in the aromatic ring affect the XB properties of iodide substituents in ortho, meta, and para positions. The effect depends on the electron-withdrawing/electron-donating properties of the substituent. Thus, electron-donating substituents with a positive mesomeric effect favor m-iodines to act as XB donors. In contrast, electron substituents with a negative mesomeric effect favor o- and p-iodines to act as XB donors. Furthermore, the stronger the mesomeric effect of the EWG or EDG substituent, the higher the effect it has on the size of the σ-hole and, consequently, on the XB donor ability of the iodide substituent.