A fluoroionophore for detection of potassium ions: 9-anthryl-substituted azacrown ether covalently linked to a 1,3-alternate calix[4]arene

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Vol. 152; no. 1; pp. 33 - 40
• Main Authors: Benco, John S, Nienaber, Hubert A, Dennen, Katherine, McGimpsey, W.Grant
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 20.09.2002; Elsevier Science
• Subjects: Analytical chemistry; Calixarenes; Chemistry; Exact sciences and technology; Fluoroionophore; General, instrumentation; Photoinduced electron transfer; Calixarenes; Fluoroionophore; Photoinduced electron transfer; Performance evaluation; Fluorescence detector; Binding capacity; Ionic selectivity; Nitrogen crown compound; Organic ligand; Alkali metal Complexes; Calixarene; Chemical sensor; Potassium Complexes
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/S1010-6030(02)00233-2

N-(9-methyl-anthracene)-25,27-bis(1-propyloxy)calix[4]arene azacrown-5 ( II) and its model compound N-(9-anthrylmethyl)aza-18-crown-6 ( I) were synthesized and tested as fluoroionophores for the selective detection of potassium ions with a view to the use of II in the fabrication of potassium ion sensors. Compound II consists of a 1,3-alternate calix[4]arene group covalently linked to an azacrown ether that is N-substituted with a fluorescent anthracene group. This compound acts as an ‘off–on’ fluorescent indicator for ion complexation. In dichloromethane solution, compound II exhibits good sensitivity to potassium ions and forms a 1:1 fluoroionophore–ion complex. Studies demonstrate that II is selective for potassium over other alkali metal cations, with excellent selectivity over sodium and lithium ( log K K, Na ∼ log K K, Li ≤−3.5) and moderate selectivity over rubidium and cesium ( log K K, Rb ∼ log K K, Cs ∼−1) . Sensitivity of II to potassium is considerably enhanced in dichloromethane in comparison to methanol/dichloromethane mixtures, presumably due to two effects: a hydrogen-bonding interaction of methanol with the azacrown nitrogen atom, and poor solvation of the ion by dichloromethane, the latter creating a driving force for complexation.