Chiroptical switching system based on the host-guest interaction between metal cations and poly(phenylacetylene)s bearing polycarbohydrate ionophore
Chiroptical switching system based on the host-guest interaction between metal cations and poly(phenylacetylene)s bearing polycarbohydrate ionophore
复制标题
DOI：
10.1016/j.eurpolymj.2008.06.025
复制
发表时间：
2008-09
影响因子：
6
通讯作者：
I. Otsuka;R. Sakai;R. Kakuchi;T. Satoh;T. Kakuchi
中科院分区：
文献类型：
--
作者：
I. Otsuka;R. Sakai;R. Kakuchi;T. Satoh;T. Kakuchi
合成了具有不同聚合度（DP）的多糖大分子单体，即带有4-乙炔基苯甲酰基的末端官能化（1→6）-2，5-脱水-3，4-二-O-乙基-d-葡萄糖醇（大分子单体2：DP=6.6，大分子单体3：DP=9.5）。将这些大分子单体与苯乙炔（PA）以不同的摩尔比进行共聚，得到了以多糖离子载体为接枝链的聚苯乙炔（poly（2x-co-PAy）和poly（3x-co-PAy））。这些聚合物在共轭聚合物主链的长吸收区（280- 500 nm）显示出分裂型圆二色性（CD）光谱。这表明聚-（2x-co-PAy）和聚-（3x-co-PAy）在主链中主要具有单手螺旋构象。这些聚合物的CD光谱图案在金属阳离子客体分子的存在下被反转。另一方面，使用带有单碳水化合物（聚-（4x-co-PAy））和金属阳离子的聚（苯乙炔）的对照实验没有显示出这样的CD光谱反转。这些结果清楚地表明，手旋光开关的聚苯乙炔轴承聚碳水化合物离子载体是由于主-客体络合的聚碳水化合物离子载体与金属阳离子。
Polycarbohydrate macromonomers with different degrees of polymerization (DP), that is, end-functionalized (1→6)-2,5-anhydro-3,4-di-O-ethyl-d-glucitols with 4-ethynylbenzoyl groups (macromonomer 2: DP=6.6, and macromonomer 3: DP=9.5) were synthesized. The copolymerizations of these macromonomers and phenylactylene (PA) were carried out in various molar ratios to give poly(phenylacetylene)s bearing a polycarbohydrate ionophore as the graft chain with various grafting rates, poly-(2x-co-PAy) and poly-(3x-co-PAy). These polymers showed split-type circular dichroism (CD) spectra in the long absorption region of the conjugated polymer backbones (280–500nm). This indicated that poly-(2x-co-PAy) and poly-(3x-co-PAy) had predominantly one-handed helical conformations in the backbones. The CD spectral patterns of these polymers were inverted in the presence of metal cationic guest molecules. On the other hand, control experiments using poly(phenylacetylene)s bearing a monocarbohydrate (poly-(4x-co-PAy)) and metal cations did not show such a CD spectral inversion. These results clearly indicated that the chiroptical switching of the poly(phenylacetylene)s bearing polycarbohydrate ionophore was attributable to the host–guest complexation of the polycarbohydrate ionophore with metal cations.