Casas-Solvas Juan M, Ortiz-Salmerón Emilia, Fernández Ignacio, García-Fuentes Luís, Santoyo-González Francisco, Vargas-Berenguel Antonio
Area de Química Orgánica, Universidad de Almería, 04120 Almería, Spain.
Chemistry. 2009 Aug 17;15(33):8146-62. doi: 10.1002/chem.200900593.
Ferrocene with a beta-cyclodextrin unit bound to one or both cyclopentadienyl rings through the secondary face were conveniently synthesized by regiospecific copper(I)-catalyzed cycloaddition of 2-O-propargyl-beta-cyclodextrin to azidomethyl or bis(azidomethyl)ferrocene. The supramolecular behavior of the synthesized conjugates in both the absence and presence of bile salts (sodium cholate, deoxycholate, and chenodeoxycholate) was studied by using electrochemical methods (cyclic and differential pulse voltammetry), isothermal titration calorimetry, and NMR spectroscopy (PGSE, CPMG, and 2D-ROESY). These techniques allowed the determination of stability constants, mode of inclusion, and diffusion coefficients for complexes formed with the neutral and, in some cases, the oxidized states of the ferrocenyl conjugates. It was found that the ferrocenyl conjugate with one beta-cyclodextrin unit forms a redox-controllable head-to-head homodimer in aqueous solution. The ferrocene-bis(beta-cyclodextrin) conjugate is present in two distinguishable forms in aqueous solution, each one having a different half-wave oxidation potential for the oxidation of the ferrocene. By contrast, only one distinguishable form for the oxidized state of the ferrocene-beta-cyclodextrin conjugate is detectable. The redox-sensing abilities of the synthesized conjugates towards the bile salts were evaluated based on the observed guest-induced changes in both the half-wave potential and the current peak intensity of the electroactive moiety.
通过区域特异性铜(I)催化的2-O-炔丙基-β-环糊精与叠氮甲基或双(叠氮甲基)二茂铁的环加成反应,方便地合成了在一个或两个环戊二烯基环的次表面结合有β-环糊精单元的二茂铁。通过电化学方法(循环伏安法和差分脉冲伏安法)、等温滴定量热法和核磁共振光谱法(PGSE、CPMG和二维ROESY)研究了合成的共轭物在有无胆盐(胆酸钠、脱氧胆酸钠和鹅去氧胆酸钠)存在下的超分子行为。这些技术能够测定与二茂铁共轭物的中性态以及某些情况下的氧化态形成的配合物的稳定常数、包合模式和扩散系数。发现具有一个β-环糊精单元的二茂铁共轭物在水溶液中形成氧化还原可控的头对头同二聚体。二茂铁-双(β-环糊精)共轭物在水溶液中以两种可区分的形式存在,每种形式对于二茂铁的氧化具有不同的半波氧化电位。相比之下,对于二茂铁-β-环糊精共轭物的氧化态,只能检测到一种可区分的形式。基于观察到的客体诱导的电活性部分的半波电位和电流峰强度的变化,评估了合成的共轭物对胆盐的氧化还原传感能力。