Hisahara Yuma, Nakano Takeo, Tamiaki Hitoshi
Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan.
Department of Chemistry, Faculty of Science, Shinshu University, 3-1-1 Asahi, Matsumoto, Nagano, 390-8621, Japan.
Photochem Photobiol Sci. 2023 Oct;22(10):2329-2339. doi: 10.1007/s43630-023-00454-w. Epub 2023 Jul 18.
Chlorophyll(Chl)-a derivatives inserting an ethynylene-m-phenylene group between a zinc chlorin ring and a hydroxymethyl group, in which various substituents were introduced on the benzene spacer, were prepared as model compounds for the light-harvesting antennae (chlorosomes) of photosynthetic green bacteria. These compounds were synthesized from a C3-ethynylated Chl-a derivative via sequential Sonogashira cross-coupling reaction, and the effects of the substituents on the phenylene linker on their self-aggregation behaviors were investigated by electronic absorption, circular dichroism, and infrared absorption spectroscopic measurements. These studies exhibited that some compounds gave the disordered self-assemblies including several species; however, the zinc complex of the dimeric Chl-a derivative primarily allowed a single J-aggregate species in an aqueous Triton X-100 micellar solution. Additional control experiments revealed that its self-assembly was constructed through the hydrogen and coordination bonding involving the hydroxymethyl group on benzene ring, keto-carbonyl group at C13-position, and central zinc atom, and this is consistent with a conventional chlorosomal manner.
叶绿素（Chl）-a衍生物在二氢卟吩锌环和羟甲基之间插入一个乙炔基间亚苯基，其中在苯间隔基上引入了各种取代基，这些衍生物被制备为光合绿细菌光捕获天线（叶绿体）的模型化合物。这些化合物由C3-乙炔基化的Chl-a衍生物通过连续的Sonogashira交叉偶联反应合成，并通过电子吸收、圆二色性和红外吸收光谱测量研究了亚苯基连接基上取代基对其自聚集行为的影响。这些研究表明，一些化合物形成了包含多种物种的无序自组装体；然而，二聚体Chl-a衍生物的锌配合物在 Triton X-100 水性胶束溶液中主要形成单一的 J-聚集体物种。额外的对照实验表明，其自组装是通过涉及苯环上的羟甲基、C13位的酮羰基和中心锌原子的氢键和配位键构建的，这与传统的叶绿体方式一致。
