Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan.
Dalton Trans. 2013 Dec 7;42(45):15974-86. doi: 10.1039/c3dt51240a. Epub 2013 Jul 22.
Two new multidentate ligands, H3L(1) and H4L(2), possessing bipyridine-phenol repetitive units were designed so that the multi-metal complexation could produce a single-helical structure in a pre-programmed fashion. The ligands were synthesized by successive palladium-catalyzed coupling reactions. The complexation of H3L(1) with zinc(II) and nickel(II) acetate afforded [L(1)Zn2(OAc)] and (L(1))2Ni42, respectively. Each of the ligand moieties in these complexes formed a one-turn single helix. The zinc(II) complex [L(1)Zn2(OAc)] underwent a helix compression-extension motion in solution. The complexation of the H3L(1) ligand with iron(III) chloride gave a dinuclear complex [(HL(1))2Fe2Cl2] with a non-helical dimeric structure. The longer ligand H4L(2) afforded a trinuclear complex [L(2)Zn3(OAc)2] with a 1.5-turn single-helical structure upon complexation with zinc(II) acetate. The reaction of the H4L(2) ligand with cobalt(II) acetate under aerobic conditions gave a mixed valence complex [L(2)Co3(OAc)3(OMe)], which had two trivalent and one divalent cobalt ions. The structural features of the trinuclear complexes significantly depended on the metals; [L(2)Co3(OAc)3(OMe)] had a helical pitch of 7.6 Å, which was almost twice that of [L(2)Zn3(OAc)2] (4.0 Å).
两种新的多齿配体 H3L(1) 和 H4L(2) 具有联吡啶-苯酚重复单元，设计成可以以预定方式产生单螺旋结构的多金属络合。配体通过连续的钯催化偶联反应合成。H3L(1) 与醋酸锌和醋酸镍的络合分别得到 [L(1)Zn2(OAc)] 和 (L(1))2Ni42。这些配合物中的每个配体部分形成一个单匝单螺旋。锌(II) 配合物 [L(1)Zn2(OAc)] 在溶液中发生螺旋压缩-延伸运动。H3L(1) 配体与氯化铁的络合得到具有非螺旋二聚体结构的双核配合物 [(HL(1))2Fe2Cl2]。较长的配体 H4L(2) 与醋酸锌络合得到具有 1.5 匝单螺旋结构的三核配合物 [L(2)Zn3(OAc)2]。H4L(2) 配体与醋酸钴在有氧条件下反应得到具有两个三价和一个二价钴离子的混合价态配合物 [L(2)Co3(OAc)3(OMe)]。这些三核配合物的结构特征显著取决于金属；[L(2)Co3(OAc)3(OMe)] 的螺旋螺距为 7.6 Å，几乎是 [L(2)Zn3(OAc)2]（4.0 Å）的两倍。
