Halogenated isophthalamides and dipicolineamides: the role of the halogen substituents in the anion binding properties
作者:Giacomo Picci、Carla Bazzicalupi、Simon J. Coles、Paola Gratteri、Francesco Isaia、Vito Lippolis、Riccardo Montis、Sergio Murgia、Alessio Nocentini、James B. Orton、Claudia Caltagirone
DOI:10.1039/d0dt01492c
日期:——
novel family of amide-based receptors is herein described. Specifically, the role of the halogen substituents at the aryl moieties in the anionbinding properties of a series of halogenated isophthalamides and dipicolineamides (L1–L6) was investigated both in solution and in the solid state in order to evaluate the incidence of all possible different and combined weak host–guest interactions. Only L5 and
The chemical double mutant cycle approach has been used to investigate substituent effects on intermolecular interactions between aromatic rings and pentafluorophenyl pi -systems. The complexes have been characterised using H-1 and F-19 NMR titrations, X-ray crystal structures of model compounds and molecular mechanics calculations. In the molecular zipper system used for these experiments, H-bonds and the geometries of the interacting surfaces favour the approach of the edge of the aromatic ring with the face of the pentafluorophenyl pi -system. The interactions are generally repulsive and this repulsion increases with more electron-withdrawing substituents up to a limit of +2.2 kJ mol(-1), when the complex distorts to minimise the unfavourable interaction. Strongly electron-donating groups cause a chance in the geometry of the aromatic interaction and attractive stacking interactions are found (- 1.6 kJ mol(-1) for NMe2). These results are generally consistent with an electrostatic model: the polarisation of the pentafluorophenyl ring leads to a partial positive charge located at the centre and this leads to repulsive interactions with the positive charges on the protons on the edge of the aromatic ring; when the aromatic ring has a high pi -electron density there is a large electrostatic driving force in favour of the stacked geometry which places this pi -electron density over the centre of the positive charge on the pentafluorophenyl group.
A Supramolecular System for Quantifying Aromatic Stacking Interactions
作者:Harry Adams、Christopher A. Hunter、Kevin R. Lawson、Julie Perkins、Sharon E. Spey、Christopher J. Urch、John M. Sanderson
A supramolecular complex for investigating the thermodynamic properties of intermolecular aromatic stackinginteractions has been developed. The conformation of the complex is locked in a single well-defined conformation by an array of H-bonding interactions that force two aromatic rings on one end of the complex into a stacked geometry. Chemical double-mutant cycles have been used to measure an anthracene-aniline