Organometallic Receptors for Biologically Interesting Molecules
ABSTRACT Trinuclear organometallic macrocycles are able to complex amino acids and peptides in aqueous solution. The complexation, which is driven by hydrophobic and π − π interactions, induces a large shift of the 1H NMR signals of the guest. The organometallic host can thus be employed as an NMR shift reagent. Structurally related trinuclear macrocycles selectively bind lithium and fluoride ions in protic as well as non-protic solvents. The binding event can be followed electrochemically or can be transduced via a subsequent chemical reaction into a change of color, which offers the possibility to construct chemosensors for these ions. The organometallic complex [Cp*RhCl2]2 can be combined with the dye azophloxine to build an indicator displacement assay for the sequence-specific detection of histidine- and methionine-containing peptides. The assay allows one to detect peptides with His/Met residues close to the N-terminus down to a concentration of 0.3 μM in water at neutral pH.
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ABSTRACT: The anion-templated syntheses and binding properties of novel macrocyclic oligopyrrole receptors in which pyrrole rings are linked through amide or imine bonds are described. The efficient synthesis was accomplished by anion-templated [1+1] Schiff-base condensation and acylation macrocyclization reactions. Free receptors and their host-guest complexes with hydrochloric acid, acetic acid, tetrabutylammonium chloride, and hydrogen sulfate were analyzed by single-crystal X-ray diffraction analysis. Stability constants with different tetrabutylammonium salts of inorganic acids were determined by standard 1H NMR and UV/Vis titration techniques in [D6]DMSO/0.5% water solution. According to the titration data, receptors containing three pyrrole rings (10 and 12) exhibit high affinity (log Ka=5-7) for bifluoride, acetate, and dihydrogen phosphate, and interact weakly with chloride and hydrogen sulfate. The amido-bipyrrole receptors 11 and 13 with four pyrrole rings exhibit 10(4)- and 10(2)-fold selectivity for dihydrogen phosphate, respectively, as inferred from competitive titrations in the presence of tetrabutylammonium acetate.Chemistry 10/2008; 14(29):9065-73. DOI:10.1002/chem.200800860 · 5.70 Impact Factor