Department of Chemistry, Colorado State University, Fort Collins, CO 80523-1872, USA.
Dalton Trans. 2012 Oct 28;41(40):12577-85. doi: 10.1039/c2dt31213a.
We report the syntheses, characterisations, and spin state behaviours of salts of the tripodal-ligated Fe(II) complex [FeL(6-OH)]X(2) (L(6-OH) = tris{4-[(6-methanol)-2-pyridyl]-3-aza-3-butenyl}amine, X = OTf(-) (1), Br(-) (2), I(-) (3), BPh(4)(-) (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 (L(2) = 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 (T(1/2) = 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 FeL(6-OH) 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.
我们报告了三脚架配体的 Fe(II)配合物[FeL(6-OH)]X(2)（L(6-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)，BPh(4)(-) (4)）盐的合成、表征和自旋态行为。配体臂的共价连接是必不可少的，因为当使用未键合的乙基亚氨基吡啶配体（L(2) = 4-[(6-甲醇)-2-吡啶基]-3-氮杂-3-丁烯基）时，会形成高自旋双（三齿）配合物（5）。对于盐 1-4，在固态中观察到热诱导自旋交叉（SCO），其依赖于阴离子和溶剂分子。具有较大阴离子的盐显示更完全的 SCO，中心温度更高（1 > 3 > 2）；三氟甲磺酸盐 1（T(1/2) = 173 K）也显示出所研究化合物中最强的协同性。氢键似乎对这类盐的 SCO 至关重要：通过使用四苯硼酸盐限制相互作用会产生低至 5 K 的高自旋配合物。在甲醇等质子溶剂中，FeL(6-OH)的光谱在三天内基本保持不变，但在与强场双齿配体相互作用时会解离。化合物 1-3 和 5 在溶液中保持高自旋，低至 180 K，与固态数据一致。
