Actinide Selective Systems for Environmental Extraction and Sensing Applications
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1104-NN05-02
Actinide Selective Systems for Environmental Extraction and Sensing Applications Xianghong Wu, Mohan Singh Bharara, Brandon K Tate, Stephen A Tonks, Jonah Z Vilseck, and Anne Elizabeth Vivian Gorden Chemistry and Biochemistry, Auburn University, 179 Chemistry, Department of Chemistry and Biochemistry, Auburn, AL, 36849 ABSTRACT The potential environmental and health concerns surrounding actinides and the use of nuclear fuels limits the acceptance of nuclear power by the public. This in turn, hinders the capability of this country to take advantage of nuclear power. Expanding our fundamental knowledge of actinide coordination chemistry will allow for the development of improved actinide sensors, new separations methods, or new means of radioactive waste remediation. We have designed and optimized a solution-phase parallel method for the synthesis of a library of symmetrical 2-quinoxalinol salens, Schiff-base type ligands with a 2-quinoxalinol incorporated into the salen backbone. This combines the rigid salen coordination framework with the quinoxaline properties that impart properties for use in colorimetric or fluorescent sensors. These have now been incorporated into organic soluble resins for metal extraction. INTRODUCTION Salen ligands and related Schiff-base ligands have been of interest to chemists due to their ease of preparation and their ability to form stable metal complexes. For example, copper (I) salen complexes have been investigated as an antitumor agents and found to be more bioactive than the antitumor drug cisplatin.1 Salen-based ligands have been most widely used as supports for stereoselective catalysis in asymmetric epoxidation,2 Hetero-Diels-Alder reactions,3 hydrocyanation,4 and other reactions.5 Derivatives of quinoxalines are key intermediates in bioactive agents used in agriculture6, or in dyes,7 and have been key intermediates in medicinal chemistry.8 Combining the salen ligand with a 2-qunioxalinol backbone produced the 2qunioxalinol salen Schiff-base type ligands was expected to be of interest for use in sensors for detecting actinide metal ions or for use in metal extractions for environmental remediation or as a metal scavenging agent for use in combinatorial chemistry. A solution-phase parallel method for the synthesis of 2-quinoxalinol salen ligands was designed and optimized (See Scheme 1.). Synthetic methods with low sensitivity to water or air in solution-phase parallel reactions were coupled with convenient workup and purification procedures resulting in a small ligand library of 20 compounds (4).9 During the synthesis of this library, it was found that on reaction of the diamine with aldehyde derivatives, the singly substituted 2-quinoxalinol imines (ex. 3) were obtained as byproducts. Diamino-2-quinoxalinols (1) produce 2-quinoxalinol imines (3a) regioselectively as solely one isomer in good yield. The regioselectivity of this reaction was determined through the use of isotopic 15N labeling experiments.10 The 2-quinoxalinol imines (3a) may then be reacted without
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