CHIRALITY OF OXIDIZED AND REDUCED OCTADECAMOLYBDODIPHOSPHATE ANIONS - OBSERVATION OF A PFEIFFER EFFECT
CHIRALITY OF OXIDIZED AND REDUCED OCTADECAMOLYBDODIPHOSPHATE ANIONS - OBSERVATION OF A PFEIFFER EFFECT
复制标题
DOI：
10.1021/ic50183a004
复制
发表时间：
1978-01-01
影响因子：
4.6
通讯作者：
POPE, MT
中科院分区：
文献类型：
--
作者：
GARVEY, JF;POPE, MT
最近确定的P2Mo180626"和a-P2W180626"的结构表明钼酸盐仅具有Z) 3 对称性，因此是手性的。报道了两种配合物在固态和乙腈溶液中的红外光谱，它们证实了钼酸盐的手性不是由晶体堆积力引起的。在存在硫酸马钱子碱的情况下，杂多钼酸四丁基铵盐在乙腈中的溶液显示出以350 nm为中心的显着的正棉花效应([M] 380=+ 1.4 X 103 deg dm" 1 M" 1)。这种行为归因于普法伊弗效应，因为使用非手性聚阴离子 a-和 d-P2W180626"、z-SiMo12O404~ 和 Mo60192" 进行类似测量仅显示少量的诱导光学活性。杂多蓝色 H2P2Mov2Mol60626" 也表现出 Pfeiffer 效应，但幅度减小，并且没有光学活性与间隔电荷转移跃迁相关。对这种行为以及 P2Mo180626" 奇数还原态明显不存在的解释进行了解释。我们最近指出 1，根据仔细的 X 射线结构分析的结果，2'3 杂多阴离子 P2Mo180 626~(“P2Mo18”) 是一种特别微妙的手性。尽管P2Mo18的结构通常被表示为共享棱角的Mo06八面体和P04四面体的组合，但具有明显的整体点对称性Z) 3| i（参见图1a），钼-钼原子在其各自的MoO6八面体内的位移降低了Z）3的总对称性。如图1b所示的位移产生了交替“短”（〜1.80μ）和“长”（〜2.05μ）的Mo-O-Mo键环。该结构的手性几乎完全是由金属原子的位移引起的，因为 0.05 µ 内的 62 个氧原子形成了 Dih 对称的密堆积簇。与钼酸盐相反，相应的“同构”
Recently determined structures of P2Mo180626" and a-P2W180626" show that the molybdate has only Z) 3 symmetry and is therefore chiral. The infrared spectra of both complexes in the solid state and in acetonitrile solution are reported and they confirm that the chirality of the molybdate is not caused by crystal packing forces. Solutions of the tetrabutylammonium salt of the heteropolymolybdate in acetonitrile in the presence of/-brucine sulfate show a significant positive Cotton effect centered at 350 nm ([M] 380=+ 1.4 X 103 deg dm" 1 M" 1). This behavior is attributed to a Pfeiffer effect since analogous measurements with the nonchiral polyanions a-and d-P2W180626",¿ z-SiMo12O404~, and Mo60192" show only minor amounts of induced optical activity. The heteropoly blue H2P2Mov2Mol60626" also exhibits a Pfeiffer effect but of diminished magnitude and no optical activity is associated with the intervalence charge-transfer transitions. An explanation of this behaviorand of the apparent nonexistence of odd reduction states of P2Mo180626" is presented.We recently pointed out1 that, according to the results of careful x-ray structural analyses, 2’3 the heteropolyanion P2Mo180 626~(“P2Mo18”) is chiral in a particularly subtle fashion. Although the structure of P2Mo18 is conventionally represented as an assemblage of edge-and corner-sharing Mo06 octahedra and P04 tetrahedra, with an apparent overall point symmetry Z) 3| i (see Figure la), displacements of mo-lybdenum atoms within their respective Mo06 octahedra lower the total symmetry to Z) 3. The displacements, illustrated in Figure lb, give rise to loops of Mo-O-Mo bonds that are alternately “short”(~ 1.80 Á) and “long"(~ 2.05 Á). The chirality of the structure is caused almost entirely by the displacements of the metal atoms since the 62 oxygen atoms, within 0.05 Á, form a close-packed cluster of Dih symmetry. In contrast to the molybdate, the corresponding “isostructural”