Hogue Ross W, Feltham Humphrey L C, Miller Reece G, Brooker Sally
Department of Chemistry and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago , PO Box 56, Dunedin 9054, New Zealand.
Inorg Chem. 2016 May 2;55(9):4152-65. doi: 10.1021/acs.inorgchem.5b02851. Epub 2016 Apr 15.
Access to a new family of thioether-linked PSRT ligands, 4-substituted-3,5-bis{[(2-pyridylmethyl)sulfanyl]methyl}-4H-1,2,4-triazoles (analogues of the previously studied amino-linked PMRT ligands), has been established. Four such ligands have been prepared, PSPhT, PS(i)BuT, PS(t-Bu)PhT, and PS(Me)PhT, with R = Ph, (i)Bu, (t-Bu)Ph, and (Me)Ph, respectively. Three dinuclear colorless to pale green iron(II) complexes, Fe(II)2(PSRT)24·solvent, featuring N4S2 donor sets, were prepared. Single-crystal structure determinations on Fe(II)2(PSPhT)24·2MeCN·H2O, Fe(II)2(PSPhT)24·2(1)/2MeCN·(1)/2H2O·THF, Fe(II)2(PS(Me)PhT)24·2MeCN, and Fe(II)2(PS(i)BuT)24·4MeCN reveal that all four are stabilized in the [HS-HS] state to 100 K and that both possible binding modes of the bis-terdentate ligands, cis- and trans-axial, are observed. Variable-temperature magnetic susceptibility studies of air-dried crystals (solvatomorphs of the single crystal samples) reveal the first examples of spin crossover (SCO) for a dinuclear iron(II) complex with N4S2 coordination. Specifically, Fe(II)2(PSPhT)24·2(1)/2H2O undergoes a multistep but complete SCO from [HS-HS] to [LS-LS], whereas Fe(II)2(PS(Me)PhT)24·1(1)/2MeCN·2H2O exhibits a half-SCO from [HS-HS] to [HS-LS]. In contrast, Fe(II)2(PS(i)BuT)24·MeCN·H2O remains [HS-HS] down to 50 K. The reflectance spectrum of pale green Fe(II)2(PSPhT)24·(1)/2CHCl3·2(1)/2H2O (solvatomorph A) reveals a trace of LS character (572 nm band (1)A1g → (1)T1g). Evans' (1)H NMR method and UV-vis spectroscopy studies revealed that on cooling dark green acetonitrile solutions of these complexes from 313 to 233 K, all three undergo SCO centered at or near room temperature. The tendency of the complexes to go LS in solution reflects the electronic impact of R on the σ-donor strength of the PSRT ligand, whereas the opposite trend in stabilization of the LS state is seen in the solid state, where crystal packing effects, of the R group and solvent content, dominate the SCO behavior.
已成功获得一类新的硫醚连接的PSRT配体，即4-取代-3,5-双{[(2-吡啶基甲基)硫烷基]甲基}-4H-1,2,4-三唑（先前研究的氨基连接的PMRT配体的类似物）。已制备了四种此类配体，分别为PSPhT、PS(i)BuT、PS(t-Bu)PhT和PS(Me)PhT，其中R分别为Ph、(i)Bu、(t-Bu)Ph和(Me)Ph。制备了三种具有N4S2供体集的双核无色至浅绿色铁(II)配合物，即Fe(II)2(PSRT)24·溶剂。对Fe(II)2(PSPhT)24·2MeCN·H2O、Fe(II)2(PSPhT)24·2(1)/2MeCN·(1)/2H2O·THF、Fe(II)2(PS(Me)PhT)24·2MeCN和Fe(II)2(PS(i)BuT)24·4MeCN进行的单晶结构测定表明，所有四种配合物在[HS-HS]状态下稳定至100 K，并且观察到双齿配体的两种可能的结合模式，即顺式和反式轴向。对风干晶体（单晶样品的溶剂变体）进行的变温磁化率研究揭示了具有N4S2配位的双核铁(II)配合物自旋交叉（SCO）的首个实例。具体而言，Fe(II)2(PSPhT)24·2(1)/2H2O经历了从[HS-HS]到[LS-LS]的多步但完全的SCO，而Fe(II)2(PS(Me)PhT)24·1(1)/2MeCN·2H2O表现出从[HS-HS]到[HS-LS]的半SCO。相比之下，Fe(II)2(PS(i)BuT)24·MeCN·H2O在50 K以下仍保持[HS-HS]状态。浅绿色Fe(II)2(PSPhT)24·(1)/2CHCl3·2(1)/2H2O（溶剂变体A）的反射光谱显示出微量的LS特征（572 nm处的带(1)A1g→(1)T1g）。埃文斯(1)H NMR方法和紫外可见光谱研究表明，将这些配合物的深绿色乙腈溶液从313 K冷却至233 K时，所有三种配合物均在室温或接近室温时发生SCO。配合物在溶液中转变为LS态的趋势反映了R对PSRT配体σ供体强度的电子影响，而在固态中观察到相反的趋势，即LS态的稳定性趋势，其中R基团和溶剂含量的晶体堆积效应主导了SCO行为。
