Sun Aiwu, Lauher Joseph W, Goroff Nancy S
Department of Chemistry, State University of New York, Stony Brook, NY 11794-3400, USA.
Science. 2006 May 19;312(5776):1030-4. doi: 10.1126/science.1124621.
Conjugated organic polymers generally must include large substituents for stability, either contained within or appended to the polymer chain. In polydiacetylenes, the substituents fulfill another important role: During topochemical polymerization, they control the spacing between the diyne monomers to produce an ordered polymer. By using a co-crystal scaffolding, we have prepared poly(diiododiacetylene), or PIDA, a nearly unadorned carbon chain substituted with only single-atom iodine side groups. The monomer, diiodobutadiyne, forms co-crystals with bis(nitrile) oxalamides, aligned by hydrogen bonds between oxalamide groups and weak Lewis acid-base interactions between nitriles and iodoalkynes. In co-crystals with one oxalamide host, the diyne undergoes spontaneous topochemical polymerization to form PIDA. The structure of the dark blue crystals, which look copper-colored under reflected light, has been confirmed by single-crystal x-ray diffraction, ultraviolet-visible absorption spectroscopy, and scanning electron microscopy.
共轭有机聚合物通常必须包含大的取代基以保证稳定性，这些取代基要么包含在聚合物链中，要么连接到聚合物链上。在聚二乙炔中，取代基还发挥着另一个重要作用：在拓扑化学聚合过程中，它们控制二炔单体之间的间距以生成有序聚合物。通过使用共晶支架，我们制备了聚（二碘二乙炔），即PIDA，这是一种几乎没有修饰的碳链，仅被单原子碘侧基取代。单体二碘丁二炔与双（腈）草酰胺形成共晶，通过草酰胺基团之间的氢键以及腈与碘代炔烃之间的弱路易斯酸碱相互作用排列。在与一种草酰胺主体形成的共晶中，二炔会自发进行拓扑化学聚合形成PIDA。深蓝色晶体在反射光下呈铜色，其结构已通过单晶X射线衍射、紫外可见吸收光谱和扫描电子显微镜得到证实。
