Comparison in practical applications of crown ether sensor molecules containing an acridone or an acridine unit – a study on protonation and complex formation

• Published in: Journal of inclusion phenomena and macrocyclic chemistry 2021-10, Vol.101 (1-2), p.63-75
• Main Authors: Golcs, Ádám, Vezse, Panna, Ádám, Bálint Árpád, Huszthy, Péter, Tóth, Tünde
• Format: Article
• Language: English
• Subjects: Aqueous solutions; Chemical sensors; Chemistry; Chemistry and Materials Science; Complex formation; Complexation; Crown ethers; Crystallography and Scattering Methods; Fluorescence; Food Science; Organic Chemistry; Original Article; Protonation; Sensors
• ISSN: 1388-3127; 1573-1111
• DOI: 10.1007/s10847-021-01086-2

Crown ethers containing an acridone or an acridine unit are successfully applied opto- and electrochemical cation sensors. The heteroaromatic unit of these macrocycles can be in different forms during the applications, which have a strong influence on the sensing behavior. Moreover, in the case of acridono-macrocycles a prototropic equilibrium takes place upon complexation, which is effected by the physicochemical characteristics. A Pb 2+ -selective acridono-18-crown-6 ether and its 9-phenylacridino-analogue were used as model compounds for comparing the different forms of the heterocyclic units of these sensor molecules. Since in most practical sensor applications of the fluorescent hosts a non-neutral aqueous medium is present, studies on complexation and signaling were carried out from the aspect of the relationship among protonation, coordinating ability, complex stability and tautomeric equilibrium. A strong interdependence among these factors was found and limitations of using unsubstituted acridino- and acridono-sensor molecules in comparison with their 9-substituted-acridino-analogues were discussed. This study will hopefully serve as a useful standpoint for future development of ionophore-based sensors containing an acridone or an acridine unit.