Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Mumbai, India.
J Phys Chem B. 2012 Mar 29;116(12):3683-9. doi: 10.1021/jp212459r. Epub 2012 Mar 19.
This article reports an efficient host-assisted guest protonation mechanism in coumarin 6 (C6) dye, upon its interaction with cucurbit[7]uril (CB7) macrocycle. C6 uptakes the CB7 macrocycle both in 1:1 and 2:1 (CB7/C6) stoichiometries, which brings out a large upward pK(a) shift (from ~0.8 to 6), and facilitates the protonation of C6 at normal pH conditions, having significant photochemical implications. Controlled dissociation of the assemblies has been achieved through their response to stimuli like temperature change or metal ions. By this approach, a specific form of the guest can be activated and could provide a simple stimulus for the controlled drug/dye delivery. Furthermore, the host-assisted guest protonation improves the stability and aqueous solubility of C6 and is a promising candidate for aqueous-based supramolecular dye laser system. Such simple protocol leading to photoswitchable systems having aqueous solubility and biocompatibility can in principle be evolved into a general strategy to deliver and operate potential functional molecular components under various trigger control.
本文报道了香豆素 6（C6）染料与葫芦[7]脲（CB7）大环相互作用时，一种有效的主体辅助客体质子化机制。C6 以 1:1 和 2:1（CB7/C6）的化学计量比摄取 CB7 大环，这导致了较大的向上 pK(a)位移（从~0.8 到 6），并在正常 pH 条件下促进了 C6 的质子化，具有重要的光化学意义。通过温度变化或金属离子等刺激，控制了组装体的解离。通过这种方法，可以激活特定形式的客体，并为控制药物/染料输送提供简单的刺激。此外，主体辅助客体质子化提高了 C6 的稳定性和水溶解度，是水基超分子染料激光系统的有前途的候选物。这种简单的方案可以使具有水溶性和生物相容性的光致变色体系得到发展，原则上可以演变成在各种触发控制下输送和操作潜在功能分子组件的通用策略。
