Though anions play various important roles in biology, their detrimental effects on humans and the environment are inevitable. It has become imperative to detect them to avoid exposure. One is azide, which is used as a preservative, mutagen, biocide, and assay reagent. However, it is very toxic to living beings. It is a potent inhibitor of mitochondrial respiration. Azide causes dizziness, nausea, vomiting, diarrhea, and restlessness at low doses. Symptoms occur within minutes of exposure. It also affects the cardiovascular system, causing dilation of peripheral blood vessels, which reduces blood pressure. In fatal poisoning, it causes a rapid progressive loss of consciousness or even coma with hyporeflexia and metabolic acidosis. In our research, a polyamine macrocycle was synthesized from Schiff's base reaction of terephthalaldehyde and N-methyl-2,2_-diaminodiethalamine in high dilution followed by sodium borohydride reduction. Then, it was converted to dinuclear Cu(II) based-polyamine macrocyclic metal-organic framework. This metal-organic framework (MOF) was used to detect azide selectively over other common anions (fluoride, chloride, bromide, iodide, nitrate, perchlorate, sulfate, and phosphate) in water, showing a visual color change of MOF upon interacting with azide. Azide changes the color of MOF from light blue to deep blue. Sulfate causes the MOF to become colorless. Probably, sulfate breaks down the MOF by removing Cu(II). UV-vis titrations were used to study the binding strength of azide with MOF by fitting the change of absorbance with a 1:1 association model and found log K = 3.85, where K is a binding constant. The single-crystal X-ray diffraction method elucidated the MOF and MOF-azide bonding structures. In the MOF, the coordination geometry is square planer and coordination number is four. Two bromides are nearby the Cu(II) to balance the charges. The Cu(II)-Cu(II) distance is 7.104 angstrom. In the MOF-azide, the coordination geometry of Cu(II) is square pyramidal and the coordination number is five. Two bromides are nearby the Cu(II) to balance the charges. The Cu(II)-Cu(II) distance is 6.961 angstrom. The detailed work will be presented in the poster session.

Acknowledgment: The research was funded by the National Science Foundation CAREER award (CHE-1056927) to Dr. Md Alamgir Hossain and LSMAMP Bridge to the Doctorate (National Science Foundation Grant-HRD-1906146). This research acknowledges US Department of Defense (Grant number W911NF-19-1-0006) and the National Science Foundation (Grant CHE-0130835). It also acknowledge Eastern New Mexico University for supporting an undergraduate student.