Studies on the synthesis of two hydrophilic hypocrellin derivatives with enhanced absorption in the red spectral region and on their photogeneration of O2− and O2(1Δg)

To improve hydrophilicity and photoactivity of the new type of photosensitizer, hypocrellin, two new derivatives were synthesized through a mild reaction method between hypocrellion B (HB) and ethanolamine in tetrahydrofuran (THF) and their molecular structures were characterized by IR, NMR, MS and UV–Vis spectrometry. In the molecular structures of the two derivatives, the peri-hydroxylated perylenquinone structure of the parent HB is preserved and their photoresponses at 600–900 nm (the red spectral region) are enhanced markedly (the molar absorption coefficients at 650 nm for the two new derivatives are EAHB1 logε=3.72 and EAHB2 logε=3.91, respectively. In contrast, the parent compound HB exhibits little absorption at 650 nm). Electron paramagnetic resonance (EPR) spin trapping measurement and a 9,10-diphenylanthracene (DPA) bleaching method were employed to investigate the photodynamic action of two chemicals in the presence of oxygen. The quantum yields of O2(1Δg) generation of EAHB1 and EAHB2 are 0.08 and 0.45, respectively; the relative quantum yields of (O2−) generation of EAHB1 and EAHB2 are 0.15 and 0.76, respectively, with the parent compound HB as the standard.