Formation of Porphyrin Fiber and Control of Its Electronic Process by Photon Injection

为了恢复自组织脂质卟啉铁组合的二氧配位能力，构建了两种非酶还原氧化铁金属中心的体系，并对其机制进行了研究。首先，合成了一种以轴向咪唑为共价键的新型脂质卟啉。它在水介质中自组织形成纤维聚集体（10纳米宽）。液相AFM测量结果显示，4个卟啉分子连续排列在纤维的核心，在生理条件下可以可逆地结合和释放二氧。共振拉曼光谱显示了该化合物的配位结构，测定了其与氧的结合亲和性、缔合速率常数和解离速率常数。磷脂囊泡包埋脂质卟啉铁（III）和脂质卟啉锌（II） （30-40 nmφ）的光照射诱导电子从受激的锌（II）中心向Fe（III）配合物转移。在三乙醇胺共存的情况下，铁络合物的比例增加，并能结合二氧。另一方面，脂质卟啉铁（III）盐溶液在362 nm处表现出配体-金属电荷转移（LMCT）吸收带。在少量糖（透明质酸、葡萄糖等）存在下，LMCT辐照（365 nm）导致中心铁（III）的还原，得到铁高自旋配合物。这种光还原涉及快速的分子内电子转移，并且糖本身被氧化以防止反向电子转移反应。激光光解的结果表明，高自旋配合物在100ns内形成。得到的铁（II）配合物形成稳定的二氧加合物。此外，该光还原体系可应用于白蛋白-卟啉铁（III）杂合物，其中白蛋白起电子传递者的作用。

In order to revive the dioxygen-coordination ability of the self-organized lipidporphyrinatoiron assemblies, two non-enzymatic systems to reduce the oxidized ferric metal centers have been constructed, and their mechanisms were studied.First, a new lipidporphyrin with a covalently bound axial imidazole has been synthesized. It was self-organized in aqueous media to give fibrous aggregate (10 nm width). The AFM measurement in liquid phase revealed that four porphyrin molecules continuously aligned at the fiber's core, which can reversibly bind and release dioxygen under physiological conditions. The resonance Raman spectroscopy showed the coordination structure of the dioxygen, and the dioxygen-binding affinity and dioxygen association and dissociation rate constants were also measured.Photoirradiation of phospholipid vesicle embedding lipidporphyrinatoiron(III) and lipidporphyrinato-zinc(II) (30-40 nmφ) induced electron transfer from the excited zinc(II) center to the Fe(III) complex. Under the coexistence of triethanolamine, the ratio of the ferrous complex increased and it can bind dioxygen.On the other hand, saline solution of lipidporphyrinatoiron(III) showed a ligand-to-metal charge transfer (LMCT) absorption band at 362 nm. Under the presence of small amount of saccharides (hyaluronic acid, glucose, etc.), LMCT irradiation (365 nm) led to reduction of the central ferric iron(III), giving ferrous high-spin complex. This photoreduction involves fast intramolecular electron transfer, and the saccharide itself is oxidized to prevent the back electron transfer reaction. The result of the laser-flash photolysis showed that the formation of the ferrous high-spin complex occurred within 100 ns. The obtained Fe(II) complex formed a stable dioxygen adduct complex.Furthermore, this photoreduction system could be applied to the albumin-porphyrinatoiron(III) hybrid, in which albumin played the role of the electron donner.