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Synthesis and photophysical properties of N-(5-amino-2-substituted-10-methyl-9H-benzo[a]phenoxazin-9-ylidene)ethanaminium chlorides
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1  Centre of Chemistry, University of Minho, Campus of Gualtar, 4710-057 Braga, Portugal

Abstract: The use of fluorescent probes for detection of biological and organic molecules has increased in the last years due to their high sensitivity and ease of use compared to radiochemical methods. Interference with the measurement of the label fluorescence could occur in many biological samples, which display some fluorescence of their own, usually in the blue or green region of the spectrum. Consequently, in studies with biomolecules it is desirable to improve the sensitivity of detection using dyes with absorption and fluorescence in the red or near infrared spectral region. Therefore, in these spectral regions it is possible the use of inexpensive and effective excitation sources, e.g. laser diodes.1,2 Having these facts in mind and as a continuation of our previous research,3 fluorescent benzo[a]phenoxazinium chlorides possessing different substituents at position 2, namely propoxyl, 4-ethoxy-4-oxobutoxyl or 3-carboxypropoxyl groups, and at positions 5, 9 and 10 of the tetracyclic system, the amino, ethylamino and methyl groups, respectively, were synthesised. Absorption and emission studies of all compounds were also carried out in ethanol, water and at simulated physiological conditions (pH 7.4). Acknowledgements: Thanks are due to the Foundation for Science and Technology (Portugal) for its financial support of Centre of Chemistry. The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network (RNRMN), and was purchased in the framework of the National Program for Scientific Re-equipment, contract REDE/1517/RMN/2005 with funds from POCI 2010 (FEDER) and FCT. References 1. Gonçalves, M.S.T. Chem. Rev. 2009, 109, 190. 2. Gonçalves, M.S.T. Optimized UV/Visible Fluorescent Markers in Advanced Fluorescence Reporters in Chemistry and Biology I. Fundamentals and Molecular Design, Demchenko A.P. (Volume Ed.), O.S. Wolfbeis (Series Ed.), Springer Series on Fluorescence, Vol. 8, Ch. 2, 27-64, Springer, Heidelberg, Germany, 2010. 3. a) Alves, C.M.A. et al Tetrahedron Lett. 2011, 52, 112. b) Naik, S. et al Eur. J. Org. Chem. 2011, 2491.