Falaise Clément, Assen Ayalew, Mihalcea Ionut, Volkringer Christophe, Mesbah Adel, Dacheux Nicolas, Loiseau Thierry
Unité de Catalyse et Chimie du Solide (UCCS) - UMR CNRS 8181, Université de Lille Nord de France, USTL-ENSCL, Bat C7, BP 90108, 59652 Villeneuve d'Ascq, France.
Dalton Trans. 2015 Feb 14;44(6):2639-49. doi: 10.1039/c4dt02343a.
A series of tetravalent uranium terephthalates has been solvothermally synthesized in the solvent N,N-dimethylformamide (DMF) at temperature 100-150 °C with different water amounts. Composition diagrams have been determined for the U(4+) metallic cation in the presence of terephthalic acid, and their crystal structures revealed the occurrence of two- or three-dimensional coordination polymers. In the absence of water, a mixture of two polytypes T-U(2)Cl(2)(bdc)(3)(DMF)(4) (1) and M-U(2)Cl(2)(bdc)(3)(DMF)(4) (2) has been identified at low temperature (100-110 °C) for bdc/U = 1-4 (bdc = terephthalate linker). Their structures are built up from isolated uranium centers in nine-fold coordination, surrounded by 6 carboxyl oxygen atoms, 2 oxygen atoms coming from DMF molecules and one chlorine atom. The uranium cations are linked to each other through the bdc ligand in order to generate a 3D framework. By increasing the temperature (130-150 °C), a layered like compound has been isolated, U(2)(bdc)(4)(DMF)(4) (3). It is composed of discrete actinide centers in ten-fold coordination, with 8 carboxyl oxygen atoms and 2 oxygen atoms from DMF molecules. The connection of the UO10 units with the bdc linkers generates 2D sheets. When a controlled amount of water is added to the reaction medium, the crystallization of the UiO-66-like U(6)O(4)(OH)(4)(H(2)O)(6)(bdc)(6)·10DMF solid (containing a hexanuclear sub-unit) is observed for temperature 110-120 °C and the H(2)O/U molar ratio in the range of 2-10. At higher temperature (140-150 °C), a distinct phase appeared, U(2)O(2)(bdc)(2)(DMF) (4), which consists of infinite chains of uranium centers, linked to each other via the bdc ligands. Higher water contents led to the formation of urania UO(2).
一系列四价铀的对苯二甲酸酯在溶剂N，N - 二甲基甲酰胺（DMF）中于100 - 150°C的温度下通过溶剂热法合成，水的用量不同。已确定了在对苯二甲酸存在下U(4+)金属阳离子的组成图，其晶体结构显示存在二维或三维配位聚合物。在无水情况下，在低温（100 - 110°C）下已鉴定出bdc/U = 1 - 4（bdc = 对苯二甲酸酯连接基）时，两种多晶型物T - U(2)Cl(2)(bdc)(3)(DMF)(4)（1）和M - U(2)Cl(2)(bdc)(3)(DMF)(4)（2）的混合物。它们的结构由九配位的孤立铀中心构成，周围有6个羧基氧原子、2个来自DMF分子的氧原子和1个氯原子。铀阳离子通过bdc配体相互连接以形成三维骨架。通过升高温度（130 - 150°C），分离出了一种层状化合物U(2)(bdc)(4)(DMF)(4)（3）。它由十配位的离散锕系元素中心组成，有8个羧基氧原子和2个来自DMF分子的氧原子。UO10单元与bdc连接基的连接产生二维片层。当向反应介质中加入适量水时，在温度为110 - 120°C且H(2)O/U摩尔比在2 - 10范围内时，观察到类UiO - 66的U(6)O(4)(OH)(4)(H(2)O)(6)(bdc)(6)·10DMF固体（含有六核亚单元）的结晶。在较高温度（140 - 150°C）下，出现了一种不同的相U(2)O(2)(bdc)(2)(DMF)（4），它由铀中心的无限链组成，通过bdc配体相互连接。更高的水含量导致形成二氧化铀UO(2)。
