Division of Material Sciences, Graduate School of Natural Science and Technology and ‡Faculty of Chemistry, Institute of Science and Engineering, Kanazawa University , Kakuma, Kanazawa 920-1192, Japan.
Langmuir. 2014 Jan 28;30(3):937-45. doi: 10.1021/la404079m. Epub 2014 Jan 16.
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. Formation of the ion associates was significantly dependent on the pH condition and on 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 acidic aqueous solution without protolytic demetalation in a wide range of pH values (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.
研究了带负电荷的卟啉分子在 NH2 端聚酰胺胺（PAMAM）树枝状大分子中的分子包封及其与树枝状大分子缔合物在界面处的行为。离子缔合物的形成明显依赖于 pH 值条件和树枝状大分子的代数。在很宽的 pH 值范围内（pH > 2），在酸性水溶液中，5,10,15,20-四（4-磺基苯基）卟啉（ZnTPPS（4-））与带正电荷的第四代（G4）PAMAM 树枝状大分子缔合，在没有质子化脱金属的情况下高度稳定。与锌（II）络合物相比，游离碱卟啉（H2TPPS（4-））在酸性条件下很容易质子化，即使存在树枝状大分子也是如此。此外，二质子化物种（H4TPPS（2-））n 的 J-聚集体优先在树枝状大分子上形成。通过电位调制荧光（PMF）光谱详细分析了树枝状大分子-卟啉缔合物的界面机制。PMF 结果表明，结合卟啉分子的树枝状大分子通过吸附步骤穿过带正电的水|DCE 界面转移，而从树枝状大分子中释放的卟啉离子的转移响应则在带负电的条件下观察到。与每个离子缔合体系的固有转移电位相比，卟啉离子的转移电位明显出现负移。可以从转移电位的负移来估计树枝状大分子与卟啉分子之间的离子缔合稳定性。ZnTPPS（4-）与较高代数的树枝状大分子表现出较强的相互作用，而 H2TPPS（4-）与树枝状大分子的缔合作用则较弱。
