{"id":543,"date":"2020-10-27T16:00:51","date_gmt":"2020-10-27T07:00:51","guid":{"rendered":"https:\/\/www.ee.nthu.edu.tw\/oh-e\/?p=543"},"modified":"2025-10-22T14:59:11","modified_gmt":"2025-10-22T05:59:11","slug":"interactions-between-hydrated-ceriumiii-cations-and-carboxylates-in-aqueous-solution","status":"publish","type":"post","link":"https:\/\/www.ee.nthu.edu.tw\/oh-e\/interactions-between-hydrated-ceriumiii-cations-and-carboxylates-in-aqueous-solution\/","title":{"rendered":"Interactions between hydrated cerium(III) cations and carboxylates in aqueous solution"},"content":{"rendered":"<h2>Interactions between hydrated cerium(III) cations and carboxylates in aqueous solution: Anomalously strong complex formation with diglycolate suggesting a chelate effect<\/h2>\n<p>Interactions between hydrated Ce<sup>3+<\/sup> and various carboxylates are of fundamental interest. <u>Anomalously strong interactions with Ce<sup>3+<\/sup> occur when adding diglycolic acid (DGA) into a Ce<sup>3+<\/sup> aqueous solution, unlike various other carboxylic acids. The complex formation constants of Ce<sup>3+<\/sup> with these acids are evaluated via absorption and emission spectra.<\/u> Hydrated Ce<sup>3+<\/sup> emits fluorescence with unity quantum yield; however, adding various carboxylates statically quenches the fluorescence when Ce<sup>3+<\/sup>\u2012carboxylate complexes form, because the fluorescence lifetime is constant irrespective of the carboxylate concentration. In the observed static quenching, the complex formation constants obtained from the absorption and emission spectra (K<sub>abs<\/sub> and K<sub>em<\/sub>) agree well. The binding Ce<sup>3+<\/sup> by the conjugate Lewis bases, i.e., carboxylates is approximately inversely proportional to the pH. Adding DGA into the system also statically quenches the fluorescence, but far more efficiently, even in a much weaker solution. We rigorously deduce K<sub>abs<\/sub> and K<sub>em<\/sub> of Ce<sup>3+<\/sup> with DGA without any approximation using comparable concentrations. Careful fittings provide equivalent K<sub>em<\/sub> and K<sub>abs<\/sub> values, and varying the pH and ionic strength confirms this equivalence is an inherent property of the Ce<sup>3+<\/sup>-DGA system. Lewis acid\u2013base theory cannot explain DGA binds Ce<sup>3+<\/sup> ~1000 times more strongly than the other carboxylates. This anomalously strong binding may be due to a chelate effect caused by the DGA\u2019s central oxygen atom, which forms a five-membered ring with the conjugate Lewis bases of DGA; double chelate rings can also form, while bis-deprotonated DGA binds Ce<sup>3+<\/sup>, facilitated by the central oxygen. Therefore, DGA enables efficient quenching through the chelate effect when it binds Ce<sup>3+<\/sup>.<\/p>\n<figure><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.ee.nthu.edu.tw\/oh-e\/wp-content\/uploads\/2020\/10\/CeriumDGA-1.jpg\" alt=\"\" class=\"aligncenter size-full\" width=\"850\" height=\"474\"\/><figcaption>Anomalously strong interactions between Ce<sup>3+<\/sup> and diglycolate have been discovered in a Ce<sup>3+<\/sup>-containing aqueous solution by observing the far more efficient static quenching of fluorescence, in contrast with a series of different carboxylates. This anomalously strong binding between Ce<sup>3+<\/sup> and diglycolate goes beyond Lewis acid\u2013base theory and may be due to a chelate effect caused by the central oxygen atom of the diglycolate molecule.<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>Interactions between hydrated cerium(III) cations and carboxylates in aqueous so &#8230; <\/p>\n","protected":false},"author":1,"featured_media":883,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-543","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"_links":{"self":[{"href":"https:\/\/www.ee.nthu.edu.tw\/oh-e\/wp-json\/wp\/v2\/posts\/543","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ee.nthu.edu.tw\/oh-e\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ee.nthu.edu.tw\/oh-e\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ee.nthu.edu.tw\/oh-e\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ee.nthu.edu.tw\/oh-e\/wp-json\/wp\/v2\/comments?post=543"}],"version-history":[{"count":9,"href":"https:\/\/www.ee.nthu.edu.tw\/oh-e\/wp-json\/wp\/v2\/posts\/543\/revisions"}],"predecessor-version":[{"id":1317,"href":"https:\/\/www.ee.nthu.edu.tw\/oh-e\/wp-json\/wp\/v2\/posts\/543\/revisions\/1317"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.ee.nthu.edu.tw\/oh-e\/wp-json\/wp\/v2\/media\/883"}],"wp:attachment":[{"href":"https:\/\/www.ee.nthu.edu.tw\/oh-e\/wp-json\/wp\/v2\/media?parent=543"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ee.nthu.edu.tw\/oh-e\/wp-json\/wp\/v2\/categories?post=543"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ee.nthu.edu.tw\/oh-e\/wp-json\/wp\/v2\/tags?post=543"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}