As a first step towards amphiphilic spin crossover (SCO) systems where the hydrophobic part of the system is introduced by a non-coordinating anion (i.e. where no modification of the ligands to introduce hydrophobic substituents is required), [FeII(OH2)2(C16SO3)2] and [CoII(OH2)2(C16SO3)2] have been prepared and reacted with the triazole-containing ligands adpt and pldpt (C16SO3 = hexadecanesulfonate anion, adpt = 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole, pldpt = 4-pyrrolyl-3,5-bis(2-pyridyl)-1,2,4-triazole). In the solid state, two HS complexes of the form [FeII(Rdpt)2(C16SO3)2] and two of the form [CoII(Rdpt)2(CH3OH)2](C16SO3)2 are obtained, even when a six-fold excess of ligand is used (Rdpt = adpt or pldpt). In solution, the cobalt complexes remain in this form as evidenced by colour, Visible/NIR and IR spectroscopy. For the iron complexes, there is an equilibrium in solution between the neutral high-spin form of the complex [FeII(Rdpt)2(C16SO3)2] and the dicationic low-spin tris form [FeII(Rdpt)3](C16SO3)2. Polar solvents favour the dicationic form, while less polar solvents favour the neutral form (as evidenced by solution colour and solution IR spectroscopy). Visible/NIR spectroscopy and Evansâ method NMR spectroscopy show the equilibrium can be shifted towards the [FeII(Rdpt)3](C16SO3)2 form by adding additional ligand to the solution. The X-ray crystal structures of [FeII(adpt)2(C16SO3)2] and [CoII(adpt)2(CH3OH)2](C16SO3)2·1.33CH3OH are presented. [FeII(adpt)2(C16SO3)2] has a 2D bilayer structure with alternating layers of polar Fe(adpt)2 centres, and hydrophobic alkyl chains. The complex cations in [CoII(adpt)2(CH3OH)2](C16SO3)2·1.33CH3OH form 1-D columns in the solid state. The capacity of the amphiphilic complexes [FeII(pldpt)2(C16SO3)2] and [FeII(adpt)2(C16SO3)2] to self-assemble has been probed at the airâwater interface using Langmuir techniques. The pertinent pressure-area isotherms reveal only a low tendency of the complexes to form films.
作为向两亲自旋交叉(SCO)系统迈出的第一步,该系统的疏
水部分是由非配位阴离子引入的(也就是说制备了[FeII(OH2)2(C16SO3)2]和[CoII(OH2)2(C16SO3)2],并与含三唑
配体 adpt 和 pldpt 进行了反应(C16SO3 =
十六烷磺酸阴离子、adpt = 4-
氨基-3,5-双(2-
吡啶基)-
1,2,4-三唑,ldpt = 4-
吡咯基-3,5-双(2-
吡啶基)-
1,2,4-三唑)。在固态下,即使使用六倍过量的
配体(Rdpt = adpt 或 pldpt),也能得到两种形式为 [FeII(Rdpt)2(C16SO3)2] 的 HS 复合物和两种形式为 [CoII(Rdpt)2(CH3OH)2](C16SO3)2 的复合物。从颜色、可见光/近红外光谱和红外光谱来看,
钴络合物在溶液中保持这种形态。对于
铁络合物,溶液中的中性高自旋络合物[FeII(Rdpt)2(C16SO3)2]和二阳离子低自旋三络合物[FeII(Rdpt)3](C16SO3)2之间存在平衡。极性溶剂有利于二阳离子形式,而极性较弱的溶剂则有利于中性形式(从溶液颜色和溶液红外光谱可以看出)。可见/近红外光谱和 Evansâ 法核磁共振光谱显示,通过在溶液中添加额外的
配体,平衡可以向[FeII(Rdpt)3](C16SO3)2 的形式转变。本文展示了[FeII(adpt)2(C16SO3)2]和[CoII(adpt)2(CH3OH)2](C16SO3)2Â-1.33CH3OH的X射线晶体结构。[FeII(adpt)2(C16SO3)2]具有二维双层结构,极性的 Fe(adpt)2 中心和疏
水的烷基链交替分布。CoII(adpt)2(CH3OH)2](C16SO3)2Â-1.33CH3OH中的复合阳离子在固态下形成1-D柱。利用 Langmuir 技术探测了两亲络合物 [FeII(pldpt)2(C16SO3)2] 和 [FeII(adpt)2(C16SO3)2] 在空气和
水界面的自组装能力。相关的压力-面积等温线显示,这些复合物形成薄膜的倾向性很低。