While the BF3 complexes of meso-tetra(aryl)porphyrins are readily decomposed into their components under aqueous conditions, immobilization of meso-tetrakis(N-methylpyridinium-4-yl)porphyrin (H2TMPyP) on a nanosized polymer (sodium salt of Amberlyst 15, nanoAmbSO3Na) formed a water-stable BF3 complex applicable for efficient aerobic photooxidation of 1,5-dihydroxylnaphthalene and sulfides under green conditions. NanoAmbSO3@H2TMPyP(BF3)2 was characterized by diffuse reflectance UV-vis spectroscopy, dynamic light scattering, thermal gravimetric analysis, Brunauer-Emmett-Teller analysis, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy techniques. The catalyst was successfully used for 10 consecutive reactions with no detectable degradation of the complex and decrease in the catalyst activity. NanoAmbSO3@H2TMPyP(BF3)2 was also completely stable toward dissociation to its components under different light conditions in acetonitrile. The singlet oxygen quantum yields φΔ of H2TMPyP, nanoAmbSO3@H2TMPyP, and their molecular complexes with BF3, determined chemically by using 1,3-diphenylisobenzofuran, revealed substantially higher values in the case of the heterogenized porphyrin and molecular complex.
Keywords: Lewis acid; aerobic photooxidation; boron trifluoride; molecular complex; photosensitizer; porphyrin; singlet oxygen.