Buffeteau Thierry, Pitrat Delphine, Daugey Nicolas, Calin Nathalie, Jean Marion, Vanthuyne Nicolas, Ducasse Laurent, Wien Frank, Brotin Thierry
Bordeaux University, Institut des Sciences Moléculaires, CNRS UMR 5255, 33405 Talence, France.
Phys Chem Chem Phys. 2017 Jul 19;19(28):18303-18310. doi: 10.1039/c7cp02045g.
The two enantiomers of cryptophane-111 (1), which possesses the most simplified chemical structure of cryptophane derivatives and exhibits the highest binding constant for xenon encapsulation in organic solution, were separated by HPLC using chiral stationary phases. The chiroptical properties of [CD(+)]-1 and [CD(-)]-1 were determined in CHCl and CHCl solutions by polarimetry, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and Raman optical activity (ROA) experiments and were compared to those of cryptophane-222 (2) derivative. Synchroton Radiation Circular Dichroism (SRCD) spectra were also recorded for the two enantiomers of 1 to investigate low-lying excited states in the B region. Time-dependent density functional theory (TDDFT) calculations of the ECD and SRCD as well as DFT calculations of the VCD and ROA allowed the [CD(-)]-PP-1 and [CD(+)]-MM-1 absolute configurations for 1 in CHCl and CHCl solutions. Similar configurations were found in the solid state from X-ray crystals of the two enantiomers but the chemical structures are significantly different from the one calculated in solution. In addition, the chiroptical properties of the two enantiomers of 1 were independent of the nature of the solvent, which is significantly different to that observed for cryptophane-222 compound. The lack of solvent molecule (CHCl or CHCl) within the cavity of 1 can explain this different behaviour between 1 and 2. Finally, we show in this article that the encapsulation of xenon by 1 can be evidenced by ROA following the symmetric breathing mode of the cryptophane-111 skeleton at 150 cm.
穴番 -111（1）是穴番衍生物中化学结构最为简化的一种，在有机溶液中对氙气封装表现出最高的结合常数。其两种对映体通过使用手性固定相的高效液相色谱法（HPLC）进行分离。通过旋光法、电子圆二色光谱（ECD）、振动圆二色光谱（VCD）和拉曼光学活性（ROA）实验，在CHCl₃和CDCl₃溶液中测定了[CD(+)]-1和[CD(-)]-1的手性光学性质，并与穴番 -222（2）衍生物的性质进行了比较。还记录了1的两种对映体的同步辐射圆二色光谱（SRCD），以研究B区域的低激发态。通过对ECD和SRCD进行含时密度泛函理论（TDDFT）计算以及对VCD和ROA进行密度泛函理论（DFT）计算，确定了1在CHCl₃和CDCl₃溶液中的[CD(-)]-PP-1和[CD(+)]-MM-1绝对构型。从两种对映体的X射线晶体在固态中发现了类似的构型，但化学结构与溶液中计算的结构有显著差异。此外，1的两种对映体的手性光学性质与溶剂性质无关，这与穴番 -222化合物的情况显著不同。1的空腔内不存在溶剂分子（CHCl₃或CDCl₃）可以解释1和2之间这种不同的行为。最后，我们在本文中表明，通过穴番 -111骨架在150 cm⁻¹处的对称呼吸模式的ROA可以证明1对氙气的封装。
