Tuning of the charge in octahedral ferric complexes based on pyridoxal-N-substituted thiosemicarbazone ligands
作者:Eddy W. Yemeli Tido、Christophe Faulmann、Robby Roswanda、Auke Meetsma、Petra J. van Koningsbruggen
DOI:10.1039/b911114j
日期:——
Four novel mononuclear coordination compounds namely: [Fe(Hthpy)2](SO4)1/2·3.5H2O 1, [Fe(Hthpy)2]NO3·3H2O 2, [Fe(H2mthpy)2](CH3C6H4SO3)3·CH3CH2OH 3 and [Fe(Hethpy)(ethpy)]·8H2O 4, (H2thpy = pyridoxalthiosemicarbazone, H2mthpy = pyridoxal-4-methylthiosemicarbazone, H2ethpy = pyridoxal-4-ethylthiosemicarbazone), were synthesized in the absence or presence of organic base, Et3N and NH3. Compounds 1 and 2 are monocationic, and were prepared using the singly deprotonated form of pyridoxalthiosemicarbazone. Both compounds crystallise in the monoclinic system, C2/c and P21/c space group for 1 and 2, respectively. Complex 3 is tricationic, it is formed with neutral bis(ligand) complex and possesses an interesting 3D channel architecture, the unit cell is triclinic, P space group. For complex 4, the pH value plays an important role during its synthesis; 4 is neutral and crystallises with two inequivalent forms of the ligand: the singly and the doubly deprotonated chelate of H2ethpy, the unit cell is monoclinic, C2/c space group. Notably, in 1 and 4, there is an attractive infinite three dimensional hydrogen bonding network in the crystal lattice. Magnetic measurements of 1 and 4 revealed that a rather steep spin transition from the low spin to high spin Fe(III) states occurs above 300 K in the first heating step. This transition is accompanied by the elimination of solvate molecules and thus, stabilizes the high spin form due to the breaking of hydrogen bonding networks; compared to 2 and 3, which keep their low spin state up to 400 K.
四种新型单核配位化合物分别为:[Fe(Hthpy)2](SO4)1/2·3.5H2O 1、[Fe(Hthpy)2]NO3·3H2O 2、[Fe(H2mthpy)2](CH3C6H4SO3)3·CH3CH2OH 3和[Fe(Hethpy)(ethpy)]·8H2O 4,(H2thpy = 吡哆醛缩氨基硫脲,H2mthpy = 吡哆醛-4-甲硫缩氨基脲,H2ethpy = 吡哆醛-4-乙基缩氨基硫脲),在有机碱、Et3N和存在下合成。氨。化合物 1 和 2 是单阳离子的,并使用单去质子化形式的吡哆醛缩氨基硫脲制备。两种化合物均在单斜晶系中结晶,C2/c 和 P21/c 空间群分别为 1 和 2。配合物3是三阳离子的,由中性双配体配合物形成,具有有趣的3D通道结构,晶胞为三斜晶系,P空间群。对于配合物4来说,pH值在其合成过程中起着重要作用; 4为中性,与两种不等价形式的配体结晶:H2ethpy的单去质子化和双去质子化螯合物,晶胞为单斜晶系,C2/c空间群。值得注意的是,在1和4中,晶格中有一个有吸引力的无限三维氢键网络。 1 和 4 的磁测量表明,在第一个加热步骤中,在 300 K 以上,发生了从低自旋到高自旋 Fe(III) 态的相当陡峭的自旋转变。这种转变伴随着溶剂化物分子的消除,因此由于氢键网络的破坏而稳定了高自旋形式;与 2 和 3 相比,它们保持低自旋状态高达 400 K。