Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.
Inorg Chem. 2010 Dec 6;49(23):11190-8. doi: 10.1021/ic1019586. Epub 2010 Nov 10.
Reactions of a saddle-distorted Mo(V)-porphyrin complex, [Mo(DPP)(O)(H(2)O)]ClO(4) (1·ClO(4); DPP(2-) = dodecaphenylporphyrin dianion), with tetra-n-butylammonium (TBA) salts of Keggin-type heteropolyoxomatalates (POMs), α-XW(12)O(40) (X = P, n = 3, 2; X = Si, n = 4, 3; X = B, n = 5; 4), in ethyl acetate/acetonitrile gave 2:1 complexes formulated as [{Mo(DPP)(O)}(2)(HPW(12)O(40))] (5), [{Mo(DPP)(O)}(2)(H(2)SiW(12)O(40))] (6), and (n-butyl)(4)N[{Mo(DPP)(O)}(2)(HBW(12)O(40))] (7) under mild reaction conditions. The crystal structures of the complexes were determined by X-ray crystallography. In these three complexes, named Porphyrin Hamburgers, the POM binds to two Mo(V) centers of porphyrin units directly via coordination of two terminal oxo groups. In spite of the similarity of those POM's structures, those Porphyrin Hamburgers exhibit different coordination bond angles between POM and the Mo(V) center in the porphyrin: 5 and 7 show two different coordination bond angles in one molecule in contrast to 6, which exhibits only one coordination bond angle. The Porphyrin Hamburgers involve protonation of the POM moieties to adjust the charge balance, as confirmed by spectroscopic titration with bases. In the crystals, the Porphyrin Hamburgers form two-dimensional (2D) sheets in the ac plane based on π-π interactions among peripheral phenyl substituents. Stacking of the 2D sheets toward the b axis constructs a 3D layered structure involving channels running into the crystallographic [1 0 0] and [0 0 1] directions in the crystal to include solvent molecules of crystallization for 5-7, and also counter cations for 7. Three complexes were revealed to be stable enough to maintain their structures even in solutions to show molecular ion peaks in the MALDI-TOF-MS measurements. They also exhibited different electron paramagnetic resonance (EPR) signals because of the Mo(V) (S = 1/2, I = 0) centers, reflecting the difference in the crystal structures. In addition, these complexes showed reversible multistep redox processes as observed in their cyclic voltammograms in benzonitrile to demonstrate high stability throughout the redox reactions in solution.
反应的鞍形扭曲的 Mo(V)-卟啉配合物，[Mo(DPP)(O)(H(2)O)]ClO(4)(1·ClO(4); DPP(2-) = 二苯并卟啉二阴离子)，与四丁基铵盐的 Keggin 型多金属氧酸盐(POMs)，α-XW(12)O(40) (X = P，n = 3,2; X = Si，n = 4,3; X = B，n = 5，4)，在乙酸乙酯/乙腈中得到了 2:1 的配合物，其分子式为[{Mo(DPP)(O)}(2)(HPW(12)O(40))] (5)、[{Mo(DPP)(O)}(2)(H(2)SiW(12)O(40))] (6)和(n-butyl)(4)N[{Mo(DPP)(O)}(2)(HBW(12)O(40))] (7)，在温和的反应条件下。通过 X 射线晶体学确定了配合物的晶体结构。在这三个被称为卟啉汉堡的配合物中，POM 通过两个末端氧原子的配位直接与卟啉单元的两个 Mo(V)中心结合。尽管 POM 的结构相似，但这些卟啉汉堡表现出不同的 POM 和卟啉中心之间的配位键角:5 和 7 在一个分子中表现出两个不同的配位键角，而 6 只表现出一个配位键角。卟啉汉堡涉及 POM 部分的质子化以调节电荷平衡，这通过与碱的光谱滴定得到证实。在晶体中，卟啉汉堡基于外围苯基取代基之间的π-π相互作用，在 ac 平面上形成二维(2D)片层。2D 片层沿 b 轴的堆积构建了一个包含溶剂分子的 3D 层状结构，这些溶剂分子进入晶体的[1 0 0]和[0 0 1]方向，适用于 5-7 的晶体，也适用于 7 的抗衡阳离子。这三个配合物足够稳定，可以在溶液中保持其结构，在 MALDI-TOF-MS 测量中显示分子离子峰。它们还表现出不同的电子顺磁共振(EPR)信号，因为 Mo(V)(S = 1/2，I = 0)中心反映了晶体结构的差异。此外，这些配合物在苯腈中的循环伏安法中表现出可逆的多步氧化还原过程，表明它们在溶液中的氧化还原反应中具有很高的稳定性。
