Cation sensing by diphenyl-azobenzocrowns

- Phenyl substituents influence cation binding of 13- and 16-membered azobenzocrowns.
- Diphenyl-azobenzocrowns are good ionophores in solid contact ion-selective electrodes.
- Phenyl substituents affect tautomeric equilibrium of hydroxyazobenzocrowns.
- Intensity of fluorescence of quinone-hydrazone forms is decreased by metal cations.

Metal cations complexation and proton binding by 13- and 16-membered diphenyl-azobenzocrowns and diphenyl-hydroxyazobenzocrowns were studied in acetonitrile using spectroscopic methods: UV-vis spectroscopy, spectrofluorimetry, and 1H NMR spectroscopy. Phenyl moieties in benzene rings were found to affect binding strength alkali and alkaline earth metal cations and hydrogen ion, and affect tautomeric equilibrium of hydroxyazobenzocrowns. X-ray structure of 13-membered diphenyl-hydroxyazobenzocrown was solved showing the existence of this compound in quinone-hydrazone form in a solid state. The suitability of diphenyl-azobenzocrowns for potentiometric metal cation determination using miniature, planar, all-solid-state type electrodes was also tested.

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