Castriciano Maria Angela, Romeo Andrea, Villari Valentina, Angelini Nicola, Micali Norberto, Scolaro Luigi Monsù
Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Università di Messina, Salita Sperone 31, 98166 Vill. S. Agata, Messina, Italy.
J Phys Chem B. 2005 Jun 23;109(24):12086-92. doi: 10.1021/jp0508960.
AOT/water/decane microemulsions have been used to entrap the water-soluble 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4). Quasi-elastic light scattering technique has confirmed the confinement of the porphyrin and its various aggregates into the inner water pool. Various species have been detected as function of the size of the microemulsions, concentration of the porphyrin, pH, and aging of the solutions by using a combination of UV-vis absorption, steady fluorescence emission, fluorescence lifetime measurements, and time-resolved fluorescence anisotropy. Under neutral pH conditions, the porphyrin is present as the free base monomer (S414) in the inner water compartment, and it is free to rotate when the size of the droplet is large enough and the porphyrin concentration is low. On increasing the concentration and/or decreasing the microemulsion size, a H-dimer of the free base (S406) is prevalently formed. Aging both the S414 and S406 species leads to the formation of a new species (S424), which has been postulated as a H-type dimer of the diacid porphyrin. On decreasing the pH, the species S414 and S406 almost instantaneously convert into the diacid porphyrin, which is monomeric (S434). This latter is an intermediate in the eventual formation of J-aggregated TPPS4 (S490). A marked stability has been observed for the S424 species, which do not interconvert on changing the pH of the bulk aqueous phase.
AOT/水/癸烷微乳液已被用于包封水溶性的5,10,15,20-四（4-磺酸苯基）卟啉（TPPS4）。准弹性光散射技术已证实卟啉及其各种聚集体被限制在内部水池中。通过结合紫外可见吸收、稳态荧光发射、荧光寿命测量和时间分辨荧光各向异性，已检测到各种物种随微乳液大小、卟啉浓度、pH值和溶液老化的变化情况。在中性pH条件下，卟啉以游离碱单体（S414）的形式存在于内部水相中，当液滴尺寸足够大且卟啉浓度较低时，它可以自由旋转。随着浓度增加和/或微乳液尺寸减小，游离碱的H-二聚体（S406）普遍形成。S414和S406物种的老化都会导致形成一种新物种（S424），该物种被假定为二酸卟啉的H型二聚体。降低pH值时，S414和S406物种几乎瞬间转化为二酸卟啉，它是单体形式（S434）。后者是最终形成J-聚集的TPPS4（S490）过程中的中间体。已观察到S424物种具有显著的稳定性，在改变本体水相的pH值时不会相互转化。
