Potential-Induced Aggregation of Anionic Porphyrins at Liquid|Liquid Interfaces

Abstract

The adsorption and self-aggregation of anionic porphyrins were studied at the polarized water|1,2-dichloroethane (DCE) interface by polarization-modulation total internal reflection fluorescence (PM-TIRF) spectroscopy. 5,10,15,20-Tetrakis(4-sulfonatophenyl)porphyrin diacid (HTPPS) and protoporphyrin IX (HPP) exhibited high surface activities at the interface. The selective excitation of interfacial species in PM-TIRF measurements elucidated the potential-induced aggregation mechanism of the porphyrins. The J-aggregates of HTPPS were reversibly formed only at the water|DCE interface by applying appropriate potentials even when the porphyrins exist as monomers in the aqueous and organic solutions. In the HPP system, the slow aggregation process was found in the negative potential region. The spectral characteristics and the signal phase of PM-TIRF indicated that the HPP monomers were adsorbed with relatively standing orientation and that the long axis of the J-aggregates was nearly in plane of the interface. HPP was also investigated at the biomimetic phospholipid-adsorbed water|DCE interface. The competitive adsorption of neutral glycerophospholipids effectively inhibited the potential-dependent adsorption and interfacial aggregation processes of HPP. The results demonstrated that the aggregation state of the charged species can reversibly be controlled at liquid|liquid interfaces as a function of externally applied potential.

The Assembly of Porphyrin Systems in Well-Defined Nanostructures: An Update

“…Yamamoto et al investigated the possibility of driving the aggregation of TPPS and protoporphyrin IX at the liquid–liquid interface by applying an external potential [79]. The polarization-modulation total internal reflection fluorescence (PM-TIRF) technique was used to study the self-aggregation of former porphyrin at the polarized water/dichloroethane interface (Figure 21).…”

“…Schematic representation of the aggregation and transfer of ( a ) H 2 TPPS 4− and ( b ) H 2 PP 2− at the polarized water/CH 2 Cl 2 interface. Adapted with permission from [79]. Copyright 2017, American Chemical Society.…”

Self-Assembly of Porphyrin Nanostructures at the Interface between Two Immiscible Liquids

“…Thus, we avoid acidic conditions (that would lead to the expulsion of the central metal ion), 17 as well as the use of synthetically challenging amphiphilic porphyrin molecules, 18 and more complicated routes using additives (e.g., divalent cations or surfactants) [19][20][21] or external stimuli (e.g., electric fields). [22][23][24] We chose zinc(II) meso-tetrakis (4-carboxyphenyl)porphyrin (ZnTPPc) as a prototypical model system to demonstrate this new means of self-assembly at an immiscible aqueous|organic interface.…”

Transformation of H-Aggregates and J-Dimers of Water-Soluble Tetrakis (4-carboxyphenyl) Porphyrin in Polyion Complex Micelles

“…Water-soluble porphyrins have stimulated tremendous research attention owing to their potential applications in medical science, electronic equipment, biomimetic chemistry, and materials chemistry [1,2,3,4]. Since the relevant applications of water-soluble porphyrins are closely related with their aggregates, great efforts have been devoted to studying the aggregates of water-soluble porphyrins in recent years [5,6,7,8,9]. For example, Shi and co-workers have reported that the dimer and monomer of Fe III -tetra(4-sulfonatophenyl)-porphyrin (Fe III TPPS) aggregated to form complex micelles when they adjusted the pH value [10].…”