Calix[4]pyrrole Cavitands for Supramolecular Sensing and Catalysis

This thesis deals with the design and synthesis of calix[4]pyrrole cavitand scaffolds and their use as chemosensors and ligands for supramolecular catalytic gold-complexes. For the design of the chemosensors, we chose mono-phosphonate calix[4]pyrrole (C4P). We demonstrated the importance of the polar phosphonate group and its relative orientation for the formation of inclusion complexes with creatinine derivatives. Next, we developed two different fluorescent IDAs for the sensing of creatinine (Cr, used as biomarker for kidney function) and their lipophilic version, hexylcreatinine. The complexes of the C4P receptors used in the IDAs, either with the indicators or the creatinine derivatives displayed a 1:1 stoichiometry and were thermodynamically and kinetically highly stable. Remarkably, the developed IDA using a fluorescent C4P receptor displayed a limit of detection adequate for the quantification of creatinine concentrations in the urine of healthy, as well as sick patients. In addition, we prepared a covalent chemosensor for creatinine operating through a direct BBS mechanism. Its unprecedent design allowed the direct sensing of creatinine derivatives without having to rely on IDAs. We also designed and synthesized two diastereomeric covalent chemosensors for the selective recognition of amino acids (L-proline and L-pipecolic acid) using fluorescence spectroscopy. We demonstrated that prepared chemosensors can be used in direct BBS experiments and IDAs. Finally, we synthesized two isomeric gold phosphoramidite calix[4]pyrrole coordination complexes. We evaluated their catalytic activity in the alkyne hydration reaction using a series of substrates having a terminal alkyne and a six-membered ring substituent with a carbonyl group of different polarity (basicity) and lacking of it. Using kinetic experiments, we showed that the polarity of the functional group un the cyclic residue of the substrates, as well as the orientation of the P-Au bond of the catalysts are key in understanding the outcome of the catalyzed hydration reactions of the terminal alkyne.

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