58418-63-6Relevant articles and documents
The flexibility-complementarity dichotomy in receptor-ligand interactions
Sun, Hongmei,Hunter, Christopher A.,Llamas, Eva Marina
, p. 1444 - 1453 (2015/02/19)
Synthetic supramolecular complexes provide an opportunity for quantitative systematic exploration of the relationship between chemical structure and molecular recognition phenomena. A family of closely related zinc porphyrin-pyridine complexes was used to examine the interplay of conformational flexibility and geometric complementarity in determining the selectivity of molecular recognition events. The association constants of 48 zinc porphyrin-pyridine complexes were measured in two different solvents, toluene and 1,1,2,2-tetrachloroethane (TCE). These association constants were used to construct 32 chemical double mutant cycles to dissect the free energy contributions of intramolecular H-bonds between the phenol side arms of the porphyrins and the ester or amide side arms of the pyridine ligands. Effective molarities (EM) for the intramolecular interactions were determined by comparison with the corresponding intermolecular H-bonding interactions. The values of EM do not depend on the solvent and are practically identical for amide and ester H-bond acceptors located at the same site on the ligand framework. However, there are variations of an order of magnitude in EM depending on the flexibility of the linker used to connect the H-bond acceptors to the pyridine ligands. Rigid aromatic linkers give values of EM that are an order of magnitude higher than the values of EM for the corresponding ester linkers, which have one additional torsional degree of freedom. However, the most flexible ether linkers give values of EM that are also higher than the values of EM for the corresponding ester linkers, which have one less torsional degree of freedom. Although the penalty for conformational restriction on binding is higher for the more flexible ether linkers, this flexibility allows optimization of the geometric complementarity of the ligand for the receptor, so there is a trade off between preorganization and fit.
Further studies on the biodegradation of ionic liquids
Ford, Leigh,Harjani, Jitendra R.,Atefi, Farzad,Garcia, M. Teresa,Singer, Robert D.,Scammells, Peter J.
experimental part, p. 1783 - 1789 (2011/01/12)
A range of ionic liquids (ILs) containing a pyridinium cation were synthesised and their biodegradability was evaluated using the CO2 headspace test (ISO 14593). ILs bearing a 1-(2-hydroxyethyl) side chain were prepared from either pyridine or nicotinic acid derivatives. These ILs showed high levels of biodegradation under aerobic conditions and can be classified as 'readily biodegradable'. In contrast, pyridinium ILs with methyl or ethyl ether side chains showed significantly lower levels of biodegradability in the same test. Biodegradation studies on a range of novel ILs with acetal and carbamate functionalities, as well as thiazolium-based salts, also showed low levels of mineralization.
