Synthesis, Spectroscopic and Self-Assembling Characterization of Novel Photoactive Mixed Aryl-Substituted Porphyrin

The present report is concerned with the designing, obtaining and characterization of novel light -sensitive molecules, belonging to second generation meso-tetraarylporphyrin derivatives. A new structure of A(3)B porphyrin, namely: 5-(4-pyridyl)-10,15,20-tris(4-phenoxyphenyl)-porphyrin was synthesized in fair yield by multicomponent reaction and characterized by H-1-NMR, FT-IR, UV-vis, fluorescence, MS, HPLC, TLC, AFM and XRD techniques. Tailoring porphyrins by introducing a pyridyl substituent in one of the meso-aryl groups confers some degree of hydrophilicity and may cause absorption and fluorescence emission bands in the long wavelength region. Besides, as it was expected, because of the relatively rigid planar structure, due to substitution with three phenoxy substituents, this porphyrin is characterized by a value of 0.219 for fluorescence quantum yield, a higher value in comparison with usual porphyrins. In solution, by UV-vis and fluorescence spectra, the effects of pH and concentration upon H and J aggregates of the porphyrin are discussed. Xray diffraction and atomic force microscopy investigations proved that this newly synthesized porphyrin is able to generate stable self-assembly in preferred orientations, such as multilayer of lamellar triangles, densely packed and homogeneous, with dimensions around 440 nm, finally forming pyramidal type structures. CHCl3 favors the spiral organization of the pyramids so that rings and even tubes of various diameters ranging from 1 mu m to 4.5 mu m were formed.