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Issue 7, 2005
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Nitroxides with two pK values—useful spin probes for pH monitoring within a broad range

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Abstract

A series of 4-dialkylamino-2,5-dihydroimidazole nitroxides with pyridine-4-yl, 4-dimethylaminophenyl or 4-hydroxyphenyl groups in position 2 of the imidazole ring were prepared using the reaction of RMgBr with corresponding 5-dialkylamino-4,4-dimethyl-4H-imidazole 3-oxides. The EPR spectra of the nitroxides were shown to be pH-sensitive due to consecutive protonation of the amidino moiety and the basic group(s) at position 2 of the imidazole ring. The 5,5-dimethyl-4-(dimethylamino)-2-ethyl-2-pyridine-4-yl-2,5-dihydro-1H-imidazol-1-oxyl showed a monotonic increase in the isotropic nitrogen hyperfine (hfi) coupling constant aN of 1 .4 G over a pH range from 2 to 6.5. Such a broad range of pH-sensitivity could be useful for many biophysical and biomedical applications, including pH-monitoring in the stomach.

Graphical abstract: Nitroxides with two pK values—useful spin probes for pH monitoring within a broad range

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Publication details

The article was received on 13 Dec 2004, accepted on 07 Feb 2005 and first published on 28 Feb 2005


Article type: Paper
DOI: 10.1039/B418707E
Citation: Org. Biomol. Chem., 2005,3, 1269-1274
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    Nitroxides with two pK values—useful spin probes for pH monitoring within a broad range

    I. A. Kirilyuk, A. A. Bobko, V. V. Khramtsov and I. A. Grigor'ev, Org. Biomol. Chem., 2005, 3, 1269
    DOI: 10.1039/B418707E

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