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Near-Infrared fluorophores based on N-(di)icosyl-substituted benzo[a]phenoxazinium chlorides as biomembrane probes
* 1 , 2 , 1 , 1
1  Centro de Química, Universidade do Minho, Gualtar, 4710-057 Braga, Portugal
2  Centro de Física, Universidade do Minho, Gualtar, 4710-057 Braga, Portugal

Abstract: Five benzo[a]phenoxazinium dyes containing alkyl chains with twenty carbon atoms on 5- or 9-positions of the tetracyclic ring were efficiently synthesised and characterised by UV/Visible and fluorescence spectroscopy. The absorption and emission maxima in ethanol lie in the range 627-641 nm and 645-676 nm, respectively, with quantum yields varying from 0.14 to 0.38. Preliminary photophysical studies in zwitterionic (2,3-bis(palmitoyloxy)propyl 2- (trimethylammonio)ethyl phosphate, DPPC) and cationic (N,N-dimethyl-Noctadecyloctadecan- 1-aminium bromide, DODAB) vesicles are reported showing that these molecules are able to detect the gel to liquid-crystalline lipid phase transition through variations either in H-aggregation extent or in an acid-base equilibrium.
Keywords: Benzo[a]phenoxazinium dyes; Biomembrane probes; Near-infrared fluorescent labels