Calixarenes for Biochemical Recognition and Separation

This review summarizes reference data on the molecular recognition of bioactive molecules by calixarenes. It emphasizes on selectivity, the design principles of the host molecules, and the type of interactions as basis for new analytical and separation methods. The following classes of compounds are discussed: amino acids, peptides and proteins, lectins, enzymes, nucleotides and nucleosides, saccharides, steroids and other guests. Also considered are induced chirality and calixarenes with substituents complementary to biomolecules. Enzyme mimics and amines are briefly discussed.     

IR and NMR Properties of Ionic Liquids: Do They Tell Us the Same Thing?

We used a combination of theoretical and experimental methods to derive the spectroscopic properties of imidazolium-based ionic liquids. Vibrational frequencies, NMR chemical shifts, and quadrupole coupling constants react in comparable manner to changes in the chemical environment. This suggests that both the IR and the NMR spectroscopic properties reflect a similar type of electronic perturbation caused by hydrogen bonding. These relationships of the spectroscopic properties provide detailed information about structural complexes and may thus serve as good indicators of ion-pair formation. They also help to decide which spectroscopic tool is the most sensitive for investigating molecular interactions. The measurement of only one spectroscopic property allows the prediction of other properties that cannot be so easily measured. In some cases, this is the only way to obtain reliable coupling constants for deriving molecular correlation times from macroscopic NMR relaxation times, thus opening a new path for studying structure-dynamics relations in ionic liquids.