Self-assemblies of tricationic porphyrin on inorganic polyphosphate

Abstract

Self-assemblies formed by the new synthesized tricationic porphyrin derivative (TMPyP3+) on the polyanionic inorganic polyphosphate (PPS) in aqueous solution were studied using different spectroscopic techniques and DFT calculation method. From the fluorescence quenching of the bound TMPyP3+ molecules and their Raman spectra we conclude that porphyrin chromophores form the stable π–π stacking-assemblies onto PPS polyanions. The transformation of the Soret band in absorption spectra at different PPS/TMPyP3+concentration ratios evidences that the assemblies are mixtures of J- and H-aggregates. Molecular modeling performed shows that the flexibility of PPS strand allows a realization of spiral or “face-to-face” one-dimensional structures formed by porphyrin molecules arranged in parallel and antiparallel modes. The peculiarity of PPS structure allows a formation of two porphyrin stacks on opposite sides of polymer strands that result in the appearance of higher-order aggregates. Their size was estimated from the light scattering data. Distinctions between TMPyP3+ and TMPyP4 aggregation on PPS template are discussed.