雷射捕陷誘導環糊精聚集化與結晶化及其於掌性光化學之應用

Abstract

我們成功地利用雷射捕陷誘導β-環糊精、γ-環糊精、2-蒽甲酸與其包合絡合物之聚集化及結晶化，且控制其掌性光二聚化反應。即便使用未飽和溶液，當將連續波雷射光束聚焦在溶液的表面，雷射捕陷得以誘導其聚集化及結晶化。例如使用β-及γ-環糊精的純水及重水溶液，隨著調整溶液濃度雷射強度，雷射捕陷誘發片狀或稜柱狀的結晶形。並且，參考此兩種結晶形也具有不同的結晶化及結晶溶解之現象，我們認為雷射捕陷方法提供另一種新的環糊精晶型。而在2-蒽甲酸的鹼溶液中，雷射捕陷則在焦點誘導針狀結晶。此為初次將雷射捕陷應用在除了胺基酸之外的有機物上，並成功誘導結晶化。另外在γ-環糊精及2-蒽甲酸的包合絡合物中，雷射捕陷方法在焦點誘導聚集化及結晶化。而且，我們於鹵素燈照明下進行其聚集體和結晶之掌性光二聚化反應。雖然仍需要更深入的研究及調查，但直至目前為止，我們發現其光產物的鏡像異構物過量值及在γ-環糊精內不同位向排列的2-蒽甲酸之比例與已發表過之文獻相異。關於雷射捕陷結晶化及光二聚化反應，我們認為及其機制的討論是建立在局部濃度的提升、稠密叢集體區域及其結構的形成上。

We succeeded in demonstrating laser trapping-induced assembling and crystallization of beta- or gamma-cyclodextrin (β- or γ-CD), 2-anthracenecarboxylate (2-AC), and their inclusion complexes in H2O and D2O, and performed its chiral photodimerization reaction. When an intense continuous-wave near-infrared laser beam was focused at an air/solution interface of each sample solution, their assembling or crystallization was always induced even in unsaturated solution. For β- or γ-CD in H2O and D2O solutions, laser trapping provided either plate-like or prism-like crystal at the focus, depending on laser power and initial solution concentration. Considering their morphology, crystallization and dissolution behaviors of each polymorph, a novel crystal form of CDs is considered to be realized by laser trapping. For 2-AC in base aqueous solution, needle-like crystal was always induced by laser trapping at the focus. Thus, we succeeded for the first time in demonstrating laser trapping-induced crystallization of organic compounds except amino acids. For mixed solutions of γ-CD and 2-AC, laser irradiation led to assembling and/or crystallization at/around the focus. We performed chiral photodimerization reaction for the resultant assemblies and crystals under halogen lamp illumination. Although further investigation should be necessary, we found that the enantiomeric excess of photoproducts and the ratio of relative orientation of 2-AC inside γ-CD were different from those reported on conventional photodimerization reaction. The dynamics and mechanism of the laser trapping-induced crystallization and the chiral photodimerization reaction are discussed in terms of local concentration increase, dense cluster domain formation, and cluster structure in the dense domain.