作者:Christina M. Klug、Ashley M. McDaniel、Stephanie R. Fiedler、Kelsey A. Schulte、Brian S. Newell、Matthew P. Shores
DOI:10.1039/c2dt31213a
日期:——
We report the syntheses, characterisations, and spin state behaviours of salts of the tripodal-ligated Fe(II) complex [FeL6-OH]X2 (L6-OH = tris4-[(6-methanol)-2-pyridyl]-3-aza-3-butenyl}amine, X = OTf− (1), Br− (2), I− (3), BPh4− (4)). Covalent linking of the ligand arms is imperative as a high-spin bis(tridentate) complex (5) is formed when a non-tethered ethyl iminopyridine ligand (L2 = 4-[(6-methanol)-2-pyridyl]-3-aza-3-butenyl) is used. For salts 1–4, thermally-induced spin-crossover (SCO) is observed in the solid state, with dependence on anion and solvate molecules. Salts with larger anions show more complete SCO centred at higher temperatures (1 > 3 > 2); the triflate salt 1 (T1/2 = 173 K) also shows the strongest cooperativity of the compounds examined. Hydrogen bonding appears to be critical to SCO in this family of salts: limiting interactions by use of tetraphenylborate produces a high-spin complex down to 5 K. In protic solvents such as methanol, spectra of [FeL6-OH]2+ are largely unchanged over a period of three days, but dissociate when interrogated with strong field bidentate ligands. Compounds 1–3, and 5 remain high spin in solution down to 180 K, consistent with the data obtained in the solid state.
我们报告了三方配位铁(II)络合物 [FeL6-OH]X2 盐类(L6-OH = 三4-[(6-甲醇)-2-吡啶基]-3-氮杂-3-丁烯基}胺,X = OTf- (1),Br- (2),I- (3),BPh4- (4))的合成、表征和自旋态行为。配体臂必须共价连接,因为使用非拴乙基亚氨基吡啶配体(L2 = 4-[(6-甲醇)-2-吡啶基]-3-氮杂-3-丁烯基)时,会形成高自旋双(三叉)配合物(5)。对于盐 1-4,在固态下观察到了热诱导自旋交叉(SCO),这与阴离子和溶质分子有关。阴离子较大的盐在较高温度下(1 > 3 > 2)显示出更完全的自旋交叉;三酸盐 1(T1/2 = 173 K)也显示出所研究化合物中最强的合作性。氢键似乎对该系列盐的 SCO 至关重要:通过使用四苯基硼酸盐限制相互作用,可产生低至 5 K 的高自旋复合物。在甲醇等质子溶剂中,[FeL6-OH]2+ 的光谱在三天内基本保持不变,但当使用强场双齿配体进行检测时,则会发生解离。化合物 1-3 和 5 在溶液中直到 180 K 仍保持高自旋,这与固态下获得的数据一致。