SENSORS FOR ANIONS OF ENVIRONMENTAL AND BIOMEDICAL RELEVANCE

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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. The second year's work involves the (i) continuation of the binding studies for anions with the four azamacrocyclces (L1, L2, L4 and L5) in the first year, (ii) synthesizing two new compounds (L3 and L6), (iii) NMR titrations for halides and oxoanions, (iv) determination of structures by X-ray crystallography. The synthesized macrocyclic based compounds with paraxylyl (L1) and thiophene (L2) spacers have been shown to effectively bind toxic perchlorate anion in both solution and solid states. The compounds contain suitable cavity consisting of multiple binding sites in their structural backbone. Studies showed that these macrocycles are capable of binding two perchlorates via multiple hydrogen bonds with protonated nitrogen sites, resulting into ditopic complexes in both cases. A hexaaminomacrocycle L3, containing four secondary and two tertiary amines has been synthesized and crystallized with hydrobromic acid. Structural analysis of the bromide complex suggests that the ligand in its tetrtaprotonated form, is involved in coordinating two bromides from both sides via hydrogen bonding interactions, forming a ditopic complex. A macrocyclic-based fluorescence chemosensor (L6) has been designed and synthesized from the reaction of dansyl chloride and a hexaaminomacrocycle containing four secondary and two tertiary amines. The new chemosensor has been examined for its binding ability toward phosphate, sulfate, nitrate, iodide, bromide, chloride, and fluoride by fluorescence spectroscopy in DMSO. The results indicate that the compound binds each of the anions with a 1:1 stoichiometry, showing high affinity for the oxoanions, chloride and iodide with the binding constants up to four orders of magnitude.