Synthesis and characterization of three new solid polyoxometalates based on Wells-Dawson-derived sandwich-type polyanions [Co_4(H_2O)_2(P_2W_15O_56)_2]^16−

Abstract

目的 本文旨在研究Wells-Daw-son三明治型杂多酸阴离子[Co_4(H_2O)_2(P_2W_15O_56)_2]^16−的配位能力、夹心金属离子的稳定性以及氧化还原性质,以拓展有机-无机杂化材料的种类。 创新点 1. 首次以Wells-Dawson三明治型杂多酸阴离子[Co_4(H_2O)_2(P_2W_15O_56)_2]^16−制备了有机-无机杂化材料;2. 首次实现在温和条件下取代Wells-Dawson三明治型杂多酸阴离子中的夹心金属离子。 方法 1.在温和条件下合成[Co_8(H_2O)_34(pz)_2{Co_4(H_2O)_2P_4W_30O_112}]·16H_2O,[H_3O]_4[Co_6(H_2O)_22(pz)_2{Co_4(H_2O)_2P_4W_30O_112}]·21H_2O和[H_3O]_4[Co_6(H_2O)_22{Co_4(H_2O)_2P_4W_30O_112}]·29H_2O三种杂多酸固态材料;2. 利用X-射线单晶衍射、傅里叶红外谱图、X-射线粉末衍射、热重分析和循环伏安曲线等测试与表征方法对合成的三种杂多酸固态材料进行结构和性质分析。 结论 在温和条件下制备由Wells-Dawson三明治型{Co_4P_4W_30}杂多酸构筑的三种固态配位材料,发现夹心环带中的金属阳离子能够影响杂化材料的骨架结构。此外,首次证明夹心环带中的金属阳离子在相对温和的条件下容易被环境中的过渡金属离子取代。本研究为合理设计和组装具有潜在应用前景的有机-无机杂化材料提供了有益参考。 Three polyoxometalate-based hybrid coordination materials, [Co_8(H_2O)_34(pz)_2{Co_4(H_2O)_2P_4W_30O_112}]·16H_2O (compound 1), [H_3O]_4[Co_6(H_2O)_22(pz)_2{Co_4(H_2O)_2P_4W_30O_112}]·21H_2O (compound 2), and [H_3O]_4[Co_6(H_2O)_22{Co_4(H_2O)_2P_4W_30O_112}]·29H_2O (compound 3) (pz=pyrazine), were built from the linkage of [Co_4(H_2O)_2(P_2W_15O_56)_2]^16− (abbreviated as {Co_4P_4W_30}) polyanions and pz and/or cobalt(II) cations. Although compounds 1 and 2 consisted of the same components, their lamellar networks were quite different. The inorganic lamellar network in compound 3 was constructed by connecting {Co_4P_4W_30} units with cobalt(II) cations. This work demonstrates that the coordination modes of {Co_4P_4W_30} are very sensitive to synthesis conditions, while the ring-belt tetrametals are easily substituted by different transition metal cations under mild reaction conditions.