Proton control of oxidation and spin state in a series of iron tripodal imidazole complexes
Proton control of oxidation and spin state in a series of iron tripodal imidazole complexes
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DOI：
10.1021/ic0351747
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发表时间：
2004-04-05
影响因子：
4.6
通讯作者：
Scheidt, WR
中科院分区：
文献类型：
--
作者：
Brewer, C;Brewer, G;Scheidt, WR
由三（2-氨基乙基）胺（三）与3个等量的咪唑甲醛缩合而成的三足咪唑配体H-3(1)、H-3(2)、H-3(3)与铁盐反应，生成8个新的阳离子铁（III）和铁（II）， [FeH3L]（3+或2+）和中性铁（III） FeL配合物。用电子能谱、红外光谱、紫外光谱、穆斯堡尔谱、质谱和循环伏安法对配合物进行了表征。三种配合物Fe(2)的结构。3H(2)O (C18H27FeN10O3, a = b = c = 20.2707(5), cubic, I (4) over bar 3d, Z = 16), Fe(3).4.5 h (2)O (C18H30FeN10O4.5, a = 20.9986(10), b = 11.7098(5), c = 19.9405(9), beta = 109.141(1)，单斜，P2(1)/c, Z = 8)，和[FeH3(3)](ClO4)2。在100 K下测定H2O (C18H26Cl2FeN10O9, a = 9.4848(4), b = 23.2354(9), c = 12.2048(5), beta = 111.147（1)0，单斜，P2(1)/n, Z = 4）。这些结构彼此相似，具有咪唑和亚胺氮原子表面配位的八面体铁。去质子化配体的铁（111）配合物Fe(1)、Fe(2)和Fe(3)为低自旋，而质子化的铁(i)阳离子配合物[FeH3(1)](ClO4)3和[FeH3(2)](ClO4)3分别为高自旋和自旋交叉。铁（II）阳离子配合物[FeH3(1)]S4O6, [FeH3(2)](ClO4)(2), [FeH3(3)](ClO4)(2)和[FeH3(3)][B(C6H5)(4)](2)表现出自旋交叉行为。对这一系列配合物的循环伏安测量表明，配体的完全去质子化使Fe(III)/ Fe（II）还原电位平均负移981 mV。阳离子铁（II）或铁（III）配合物[FeH3L]（3+或2+）在空气中脱质子生成中性铁（III）配合物FeL。该过程对Fe(3)可逆，其中Fe(3)质子化生成[FeH3(3)]（2+）。
Reaction of iron salts with three tripodal imidazole ligands, H-3(1), H-3(2), H-3(3), formed from the condensation of tris(2-aminoethyl)amine (tren) with 3 equiv of an imidazole carboxaldehyde yielded eight new cationic iron(III) and iron(II), [FeH3L](3+or2+), and neutral iron(III), FeL, complexes. All complexes were characterized by EA(CHN), IR, UV, Mossbauer, mass spectral techniques and cyclic voltammetry. Structures of three of the complexes, Fe(2).3H(2)O (C18H27FeN10O3, a = b = c = 20.2707(5), cubic, I (4) over bar 3d, Z = 16), Fe(3).4.5H(2)O (C18H30FeN10O4.5, a = 20.9986(10), b = 11.7098(5), c = 19.9405(9), beta = 109.141 (1), monoclinic, P2(1)/c), Z = 8), and [FeH3(3)](ClO4)2.H2O (C18H26Cl2FeN10O9, a = 9.4848(4), b = 23.2354(9), c = 12.2048(5), beta = 111.147(1)0, monoclinic, P2(1)/n, Z = 4) were determined at 100 K. The structures are similar to one another and feature an octahedral iron with facial coordination of imidazoles and imine nitrogen atoms. The iron(111) complexes of the deprotonated ligands, Fe(l), Fe(2), and Fe(3), are low-spin while the protonated iron(Ill) cationic complexes, [FeH3(1)](ClO4)3 and [FeH3(2)](ClO4)3, are high-spin and spin-crossover, respectively. The iron(II) cationic complexes, [FeH3(1)]S4O6, [FeH3(2)](ClO4)(2), [FeH3(3)](ClO4)(2), and [FeH3(3)][B(C6H5)(4)](2) exhibit spin-crossover behavior. Cyclic voltammetric measurements on the series of complexes show that complete deprotonation of the ligands produces a negative shift in the Fe(III)/ Fe(II) reduction potential of 981 mV on average. Deprotonation in air of either cationic iron(II) or iron(III) complexes, [FeH3L](3+or2+), yields the neutral iron(III) complex, FeL. The process is reversible for Fe(3), where protonation of Fe(3) yields [FeH3(3)](2+).