Komatsu Teruyuki, Moritake Miho, Tsuchida Eishun
Advanced Research Institute for Science and Engineering Waseda University, Tokyo 169-8555, Japan.
Chemistry. 2003 Oct 6;9(19):4626-33. doi: 10.1002/chem.200305013.
Novel molecular energy and electron transfer assemblies in vesicular form, which are made of self-organized amphiphilic porphyrins bearing phospholipid-like substituents (lipid-porphyrins), have been photochemically characterized. Tetraphenylporphyrin (TPP) derivatives with four dialkylphosphocholine groups [free-base (1 a), Zn(2+) complex (1 b), and Fe(3+) complex (1 c)] are spontaneously associated in water to form spherical unilamellar vesicles with a diameter of 100-150 nm. Exciton calculations based on the bilayered sheet model of 1 b, which has a porphyrin packing similar to that seen in the triclinic unit cell of the Zn(2+)TPP crystals, reproduced the Soret band bathochromic shift appearing in the aqueous solution of 1 b well. The UV/Vis absorption spectrum of the 1 a/1 b hybrid vesicles (molar ratio: 1/1) showed no electronic interaction between the two porphyrin chromophores in the ground state, but efficient intermolecular singlet-singlet energy transfer took place from the excited 1 b donors to the 1 a acceptor within the vesicle. Near-field scanning optical microspectroscopy of the 1 a/1 b vesicles on a graphite surface also showed only free-base porphyrin fluorescence. The efficiency of the energy transfer was 0.81 and the rate constant was 3.1 x 10(9) s(-1). On the other hand, protoporphyrin IX bearing two alkylphosphocholine propionates (2) was incorporated into the 1 a or 1 c bilayer vesicles (ca. 100 nm phi, molar ratio: 1 a/2 or 1 c/2=10). The UV/Vis absorption spectrum showed that 2 was successfully anchored into the fluid alkylene region of the membrane without stacking. Photoirradiation (lambda(ex): 390 nm) of the 1 c/2 vesicles in the presence of triethanolamine led a vectorial electron transfer from the outer aqueous phase to the membrane center, which allowed reduction of the ferric ion of the Fe(3+)TPP platform.
由带有类磷脂取代基的自组装两亲卟啉（脂质 - 卟啉）制成的新型囊泡状分子能量和电子转移组件已通过光化学方法进行了表征。具有四个二烷基磷酰胆碱基团的四苯基卟啉（TPP）衍生物[游离碱（1a）、Zn(2+)配合物（1b）和Fe(3+)配合物（1c）]在水中自发缔合形成直径为100 - 150 nm的球形单分子层囊泡。基于1b的双层片层模型进行的激子计算，其卟啉堆积类似于在Zn(2+)TPP晶体的三斜晶胞中观察到的堆积，很好地再现了在1b水溶液中出现的Soret带红移。1a/1b混合囊泡（摩尔比：1/1）的紫外/可见吸收光谱表明，在基态下两个卟啉发色团之间没有电子相互作用，但在囊泡内从激发的1b供体到1a受体发生了有效的分子间单重态 - 单重态能量转移。在石墨表面上对1a/1b囊泡进行的近场扫描光学显微光谱也仅显示游离碱卟啉荧光。能量转移效率为0.81，速率常数为3.1×10(9) s(-1)。另一方面，带有两个烷基磷酰胆碱丙酸酯的原卟啉IX（2）被掺入1a或1c双层囊泡（约100 nm phi，摩尔比：1a/2或1c/2 = 10）中。紫外/可见吸收光谱表明2成功地锚定在膜的流体亚烷基区域中而没有堆积。在三乙醇胺存在下对1c/2囊泡进行光照射（λ(ex)：390 nm）导致从外部水相到膜中心的矢量电子转移，这使得Fe(3+)TPP平台的铁离子得以还原。
