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  • Open access
  • 40 Reads
Protonation Studies of Schiff Bases Using 13C and 15N-NMR Spectroscopy
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13C and 15N-NMR spectroscopy provides clear evidence that the Schiff bases of 3-hydroxy-4-pyridinecarboxaldehyde exist as a mixture of hydroxyimino and oxoenamino tautomers in acid media. The study of the stabilities of the tautomeric forms has been approached using density functional calculations (B3LYP/6-31G**). The X-ray molecular structure of (E)-4-[(4-bromophenylimino)methyl]-3- hydroxypyridinium tetrafluoroborate has been solved.
  • Open access
  • 53 Reads
Syntheses of new azepane derivatives from monosaccharides
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Synthetic routes to polyhydroxy azepanes from monosaccharides are described. The stereoselective formation of trans epoxyamides and regioselective epoxyde opening led to azido derivatives that could be transformed in azepanic structures. An anomalous result was obtained in the hydrogenation in MeOH with Pd/C of the azido derivative obtained from D-mannose
  • Open access
  • 48 Reads
Synthesis and spectral characterisation of naphtho[2,3-a]phenoxazinium salts
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A series of new functionalised naphtho[2,3-a]phenoxazinium chlorides was synthesised by condensation of 5-ethylamino-2-nitrosophenol hydrochloride with 1-aminoanthracene and its N-substituted derivatives. These cationic dyes showed maximum absorption in the range between 590 and 647 nm and strong fluorescence with maximum emission wavelengths between 630 and 674 nm, as well as high fluorescent quantum yields in ethanol and water at physiological pH.
  • Open access
  • 53 Reads
Benzo[a]phenoxazine dyes as new fluorescent labels of L-valine
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Two fluorescent functionalised benzo[a]phenoxazinium chlorides were efficiently synthesised by condensation of 5-ethylamino-4-methyl-2-nitrosophenol hydrochloride with the corresponding N-substituted-naphthylamines. In order to evaluate their applicability as covalent probes for biomolecules, these heterocycles were coupled at the C-terminus of N-protected-L-valine through an ester or amide linkage. Studies of their photophysical properties revealed that all compounds absorbed and emitted at longer wavelengths with high fluorescent quantum yields.
  • Open access
  • 53 Reads
Preliminary photostability studies of benzo[a]phenoxazinium chlorides
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Photostability studies of a series of functionalised benzo[a]phenoxazinium chlorides were carried out in ethanol and water at physiological pH, under irradiation at 419 and 350 nm. These compounds showed good to excellent photostability in ethanol and moderate photostability in water in the wavelengths tested.
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