This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project involves the design and synthesis of receptors for anions of environmental and biological importance specifically. Polyazamacrocycles as receptors and oxoanions and halides were the focus during the first year. During this time, three approaches ware employed: (i) design, synthesis, and characterization of receptors, (ii) examination of the binding capabilities of the synthesized compounds for anions in solution by NMR titration technique, and (iii) investigation of solid state structures of the host-guest complexes. A thiophene based azacryptand has been synthesized, and its anion binding properties have been studied in both solid and solution states. Crystallographic studies indicate that the ligand binds one chloride or three nitrates with an in-in conformation of the bridgehead amino protons. In the chloride complex, the encapsulated anion sits in the cavity with N++++Cl? distance 3.10(1) ?, whereas, for the nitrate complex, the three anions are located in three side pockets, and are bridged through one oxygen with the two in-in protons on the apical nitrogen with an average distance of N+++O of 3.238 ?. The NMR titrations were performed for chloride, bromide, iodide, nitrate and sulfate. Results indicated that the ligand effectively binds these anions ranging from 4,000 to 100,000 M-1. Three other ligands were also synthesized that are planed to study for anions in both solution and solid states. These compounds are currently being investigated by Dr. Clement G. Yedjou (collobaroator of this project) for cytoxicity studies.
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