Abstract

The equilibrium constant of the PLLA-C₇₀ complex was determined spectrophotometrically and found at 1084 M⁻¹, a value fully comparable with the equilibrium constant of the PLLA-C₆₀ complex 956 M⁻¹. In fact, both C₆₀ and C₇₀ share practically the same electron affinity and both are able to form charge-transfer complex with poly(L-lactic acid) (PLLA) in dichloromethane solution. The PLLA-C₇₀ complex in CH₂Cl₂ solution shows also a pronounced extrinsic or induced Cotton effect when analyzed with optical rotatory dispersion (ORD) spectroscopy suggesting a kind of host-guest interaction where the helical conformation of PLLA by binding C₇₀ internally or externally to the helical coils, is able to induce the optical activity to the achiral C₇₀.

摘要

PLLA-C ₇₀复合物的平衡常数通过分光光度法测定，发现为 1084 M ^-1，该值与 PLLA-C ₆₀复合物 956 M ^-1的平衡常数完全可比。事实上，C ₆₀和C ₇₀实际上具有相同的电子亲和力，并且都能够在二氯甲烷溶液中与聚（L-乳酸）（PLLA）形成电荷转移复合物。CH ₂ Cl _{2 中}的 PLLA-C ₇₀络合物当使用旋光色散 (ORD) 光谱分析时，该溶液还显示出明显的外在或诱导棉花效应，这表明存在一种主客体相互作用，其中 PLLA 的螺旋构象通过在内部或外部将C ₇₀与螺旋线圈结合，能够诱导对非手性 C ₇₀的旋光性。