Spectroelectrochemical Characterization of Dendrimer–Porphyrin Associates at Polarized Liquid|Liquid Interfaces

Abstract

Molecular encapsulation of anionic porphyrins in NH2-terminated polyamidoamine (PAMAM) dendrimers and the interfacial behavior of the dendrimer-porphyrin associates were studied at the polarized water|1,2-dichloroethane (DCE) interface. The formation of the ion associates was significantly dependent on the pH condition and on the generation of dendrimers. 5,10,15,20-Tetrakis(4-sulfonatophenyl)porphyrin (ZnTPPS 4-) associated with the positively charged fourth generation (G4) PAMAM dendrimer was highly stabilized in the acidic aqueous solution without protolytic demetalation in a wide range of pH (pH > 2). In contrast to the zinc(II) complex, the free base porphyrin (H2TPPS 4-) was readily protonated under acidic conditions even in the presence of the dendrimers. In addition, the J-aggregates of diprotonated species, (H4TPPS 2-)n, were preferably formed on the dendrimer. The interfacial mechanism of the dendrimer-porphyrin associates was analyzed in detail by potential modulated fluorescence (PMF) spectroscopy. PMF results indicated that the dendrimers incorporating porphyrin molecules were transferred across the positively polarized water|DCE interface via adsorption step, whereas the transfer responses of the porphyrin ions released from the dendrimers were observed at negatively polarized conditions. A negative shift of the transfer potential of porphyrin ions compared to the intrinsic transfer potential was apparently observed for each ion association system. The ion association stability between the dendrimer and the porphyrin molecules could be estimated from a negative shift of the transfer potential. ZnTPPS 4-exhibited relatively strong interaction with the higher generation dendrimer, whereas H2TPPS 4-was less effectively associated with the dendrimers.3

Photoinduced Electron Transfer of PAMAM Dendrimer–Zinc(II) Porphyrin Associates at Polarized Liquid|Liquid Interfaces

“…3.5 (PAH), 10 (G4 PAMAM dendrimer), and 20 times (G2 PAMAM dendrimer) larger than for the ZnTPPS 4− system. Taking into account the adsorption of the ion associates involving ZnTPPS 4− , which increases the interfacial concentration of the photoreactant, the potential dependences of the photocurrent measured in the dendrimer−ZnTPPS 4− systems were roughly consistent with the interfacial tension lowering shown in Figure 18 The ΔG D···ZnTPPS 4− values indicate explicitly a high stability of the G4 PAMAM dendrimer−ZnTPPS 4− associate. The ZnTPPS 4− molecule can penetrate into the interior of the larger spherical G4 PAMAM dendrimer, whereas ZnTPPS 4− associated with the small flatelliptical G2 PAMAM dendrimer is exposed to the outer solution phase.…”

“…The magnitude of the real (i photo,re ) and imaginary (i photo,im ) components of the ac photocurrent measured at pH 5.3 and 7.2 increased gradually at positive potentials. In our previous study, 18 Figure 4). In general, the concentration of a surface-active ion at a polarized liquid| liquid interface is maximized around its transfer potential.…”

Molecular association between flavin derivatives and dendritic polymers at the water|1,2-dichloroethane interface

“…S4, blue lines). These PMF responses were attributed to the ion transfer and adsorption of the dendrimer-bound fluorescent LC species at the organic side of the interface [1,8]. The slight enhancement of the fluorescence intensity confirmed the interaction between LC and the dendrimer as indicated from fluorescence spectra in aqueous solutions (Fig.…”

Ion transfer and adsorption behavior of ionizable drugs affected by PAMAM dendrimers at the water|1,2- dichloroethane interface

“…The ion transfer potentials and ionic partition diagrams of HDIP + and HPRO + were, however, not shifted in the presence of the dendrimers. It has been reported that a multipoint electrostatic interaction of ionic species with the dendrimer significantly enhances the ion association stability whereas a monovalent ion is not appreciably associated with the dendrimer [23,24]. The ambiguous effects of the dendrimer for the monovalent drug cations could be due to weak interaction with the G3.5 PAMAM dendrimer.…”

“…The spectroelectrochemical analysis of charge transfer reactions elucidated the potential-driven encapsulation of anilinonaphthalenesulfonates in the carboxylate-terminated generation 3.5 (G3.5) polyamidoamine (PAMAM) dendrimer at the polarized water|DCE interface [23]. Recently, The ion association behavior of the amino-terminated PAMAM dendrimers with water-soluble porphyrins at the interface was also investigated in terms of dendritic generation, pH condition, effect of metal center and so on [24]. The PAMAM dendrimer-zinc(II) porphyrin associates showed a high photoreactivity in the heterogeneous photoinduced electron transfer system at the water|DCE interface [25].…”