Complexes produced by associated forms of porphyrin bound with hydrophobic–hydrophilic copolymer and transition metal ions

Abstract

Properties of protonated dimeric forms of meso-tetraphenylporphine (TPP) and meso-tetra( p-aminophenyl)porphine (TAPP) bound with copolymer and also complexes produced by associated TAPP bound with copolymer, Mn 2+, and Fe 3+ are investigated by absorption, luminescence, and Raman spectroscopy. According to absorption spectra of protonated dimers of TPP, three dimeric forms of the porphyrin are observed in the ground state. However, selective excitation of these forms according to the fluorescence spectra reveals only two dimeric forms in the excited state. In contrast, similar selective excitation of TAPP bound with copolymer in aqueous–dioxane solution results in weak changes in the fluorescence spectra, nevertheless, there is strong interaction between porphyrin and macromolecular carboxyl groups in the ground state. In the case of the formation of the complexes between associated TAPP bound with copolymer, Mn 2+ and Fe 3+, a new band in the near IR region with a maximum at 840 nm is built up in the fluorescence spectrum. However, this near IR emission is completely quenched when new strong vibrational bands at approximately 1800 and 1900 cm −1 are revealed in the resonance Raman spectra of the complexes. The observed effects are explained in terms of direct participation of water molecules involved in the water–porphyrin dimeric complex in the processes of transformation of excitation energy. The involvement of water in this dimeric complex can lead to redistribution of flows of the energy degradation when transition metal ions play a role of the agent which enhances the trapping properties of the porphyrin–metal-ions complexes.