Fig 1.
A. Unsubstituted furyl- and furylvinyl aryloxazoles with different aryl moieties linked to the furan ring. FN-1: 2-(furan-2-yl)benzo[1,2-d]oxazole, FN-2: (E)-2-(2-(furan-2-yl)vinyl)benzo[1,2-d]oxazole, FN-3: 2-(furan-2-yl)naphtho[2,3-d]oxazole, FN-4: (E)-2-(2-(furan-2-yl)vinyl)naphtho[2,3-d]oxazole, FN-5: (E)-2-(2-(furan-2-yl)vinyl)naphtho[1,2-d]oxazole. B. Furyl vinyl naphthoxazoles with different substituents in the furan ring. FN-6: (E)-2-(2-(5-methyl-furan-2-yl)vinyl)naphtho[1,2-d]oxazole, FN-7: (E)-2-(2-(5-methoxy-furan-2-yl)vinyl)naphtho[1,2-d]oxazole, FN-8: (E)-2-(2-(5-bromo-furan-2-yl)vinyl)naphtho[1,2-d]oxazole, FN-9: (E)-2-(2-(5-phenyl-2-furan-2-yl)vinyl)naphtho [1,2-d]oxazole.
Fig 2.
Absorption and emission spectra of probes FN-1 (A), FN-2 (B), FN-4 (C) and FN-5 (D) in solvents representatives of the polarity scale, acetonitrile (solid, black line), benzene (dash red line), dimethylformamide (dot green line), methanol (dash-dot light blue line).
Table 1.
Absorption maxima and molar absorption coefficient of furyl aryloxazoles in representative solvents of different polarity.
Table 2.
Fluorescence quantum yields for unsubstituted furyl- and furyl vinyl aryloxazoles.
Fig 3.
Evolution of the lower energy absorption band of dyads FN-2 (A), FN-3 (C), FN-4(B) y FN-5(D), due to reaction with 1O2 produced by photosensitization. Solvent: methanol; Sensitizer: NMB; Irradiation: Led, 660 nm.
Fig 4.
Changes in the fluorescence spectra of dyads FN-2 (A), FN-3 (B), FN-4(C) y FN-5(D), due to reaction with 1O2 produced by photosensitization. Solvent: methanol; Sensitizer: NMB; Irradiation: Led, 660 nm, irradiation time: 40 min. Inset: Increase of relative fluorescence with the irradiation time.
Fig 5.
Absorption and emission spectra of probes FN-6 (A), FN-7 (B), FN-8 (C) and FN-9 (D) in solvents representatives of the polarity scale: acetonitrile (solid, black line), benzene (dash red line), dimethylformamide (dot green line), methanol (dash-dot light blue line).
Table 3.
Fluorescence quantum yields for substituted furyl vinyl naphthoxazoles.
In parenthesis fluorescence lifetime in ns.
Fig 6.
Absorption spectrum changes for FN-6 (A), FN-7 (B), FN-8 (C) and FN-9 (D) upon reaction with 1O2 generated by irradiation of NMB in methanol.
Fig 7.
Fluorescence intensity changes for FN-6 (A), FN-7 (B), FN-8 (C) and FN-9 (D) upon reaction with 1O2 generated by irradiation of NMB in methanol. Inset: Fluorescence enhancement over irradiation time. Excitation wavelength was 330 nm.
Table 4.
Rate constants for overall (kq) and reactive (kr) quenching of singlet oxygen by furyl vinyl naphthoxazoles, singlet oxygen trapping efficiency (kr/kq), and quantum yields for singlet oxygen photosensitization.
Fig 8.
Linear correlation between the total rate constant for reaction of furyl vinyl naphthoxazoles and 1O2 with the F parameter of Swain and Lupton (A) and the Fukui condensed function for the electrophilic attack of 1O2 on the C-5 of furan ring (B). Solvents: ACN (black circles), methanol (red squares). Blue inverted triangles correspond to the reactive rate constant in methanol.
Fig 9.
Exciplex structure for the partially concerted cycloaddition of 1O2 to furyl-substituted vinyl naphthoxazole.