在活性位点含有3d金属高价离子的摩尔水氧化催化剂的合成可用性是实现大规模光和电化学水分解的先决条件。在这里,二铵{μ-1,3,4,7,8,10,12,13,16,17,19,22-十二-氮杂-四环-[8.8.4.13,17.18,12]四-椰草烷-5,6,14,15,20,21-六-奥托}高铁酸盐(IV)乙酸三-醇酸盐的合成和晶体结构,据报道,(NH4)2[FeIV(C12H12N12O6)]·3CH3COOH或(NH4)2[FeIV(L-6H)]·3CH3COOH。FeIV离子被大多环配体包封,可以描述为十二碳氮杂四环笼,具有两个封端三氮杂环己烷片段,形成三个五元和六个六元交替螯合环,并带有中心FeIV离子。FeIV的局部配位环境由六个去质子化的酰肼硝基原子形成,稳定不寻常的氧化状态。FeIV离子位于空间群C2/c的双重旋转轴(多重性4,Wyckoff字母e)上。其协调几何形状介于三角棱镜(畸变角φ=0°)和反棱镜(φ=60°)之间,φ=31.1°。Fe-N键的长度在1.9376(13)-1.9617(13)的范围内,正如预期的四价铁。结构分析表明,每个铁(IV)配合物另外共结晶三个乙酸分子,其中一个在四个位置上位置混乱。在晶体结构中,铵阳离子,复杂的二阴离子和乙酸摩尔离子通过复杂的氢键系统相互连接,主要通过作为受体的草酰胺氧原子。
The synthetic availability of mol-ecular water oxidation catalysts containing high-valent ions of 3d metals in the active site is a prerequisite to enabling photo- and electrochemical water splitting on a large scale. Herein, the synthesis and crystal structure of di-ammonium {μ-1,3,4,7,8,10,12,13,16,17,19,22-dodeca-aza-tetra-cyclo-[8.8.4.13,17.18,12]tetra-cosane-5,6,14,15,20,21-hexa-onato}ferrate(IV) acetic acid tris-olvate, (NH4)2[FeIV(C12H12N12O6)]·3CH3COOH or (NH4)2[FeIV(L-6H)]·3CH3COOH is reported. The FeIV ion is encapsulated by the macropolycyclic ligand, which can be described as a dodeca-aza-quadricyclic cage with two capping tri-aza-cyclo-hexane fragments making three five- and six six-membered alternating chelate rings with the central FeIV ion. The local coord-ination environment of FeIV is formed by six deprotonated hydrazide nitro-gen atoms, which stabilize the unusual oxidation state. The FeIV ion lies on a twofold rotation axis (multiplicity 4, Wyckoff letter e) of the space group C2/c. Its coordination geometry is inter-mediate between a trigonal prism (distortion angle φ = 0°) and an anti-prism (φ = 60°) with φ = 31.1°. The Fe-N bond lengths lie in the range 1.9376 (13)-1.9617 (13) Å, as expected for tetra-valent iron. Structure analysis revealed that three acetic acid mol-ecules additionally co-crystallize per one iron(IV) complex, and one of them is positionally disordered over four positions. In the crystal structure, the ammonium cations, complex dianions and acetic acid mol-ecules are inter-connected by an intricate system of hydrogen bonds, mainly via the oxamide oxygen atoms acting as acceptors.