Polymerization Studies of Diiodohexatriyne and Diiodooctatetrayne Cocrystals

The formation of
ordered polydiacetylenes (PDAs) from conjugated
triynes and longer polyynes has proven challenging due to the low
stability of the starting materials and the possibility of varying
regiochemistry for the polymerization. We report here the preparation
of host–guest cocrystals of diiodohexatriyne and diiodooctatetrayne,
each with a bis­(nitrile)­oxalamide host. Single-crystal X-ray diffraction
studies show that the halogen-bonding interactions between the host
and guest align the diiodopolyyne monomers with the proper parameters
for 1,4-topochemical polymerization. Using Raman spectroscopy, solid-state 13C MAS NMR, and single-crystal X-ray diffraction, we have
demonstrated the formation of a single highly ordered PDA, poly­(iodoethynyl­iododiacetylene)
(PIEDA), from the 1,4-polymerization of diiodohexatriyne. Diiodo­octatetrayne
also forms ordered cocrystals, but attempts to form polymer from these
crystals led to disordered species. This work represents the first
reported single-crystal-to-single-crystal 1,4-polymerization of a
conjugated triyne.

由共轭三炔（conjugated triynes）与更长链多炔（longer polyynes）制备有序聚二乙炔（polydiacetylenes, PDAs）一直存在挑战，这源于起始原料稳定性较低，且聚合过程存在区域选择性多样化的可能。本文报道了二碘己三炔与二碘辛四炔分别与双（腈基）草酰胺主体（bis(nitrile)oxalamide host）构筑的主客体共晶（host–guest cocrystals）的制备方法。单晶X射线衍射（single-crystal X-ray diffraction）研究显示，主体与客体间的卤键相互作用（halogen-bonding interactions）可使二碘多炔单体按满足1,4-拓扑化学聚合（1,4-topochemical polymerization）要求的恰当参数进行排列。通过拉曼光谱（Raman spectroscopy）、固态13C魔角旋转核磁共振谱（solid-state 13C MAS NMR）与单晶X射线衍射表征，我们证实二碘己三炔经1,4聚合可生成单一高度有序的聚（碘乙炔基碘二乙炔）（poly(iodoethynyliododiacetylene), PIEDA）。二碘辛四炔同样可形成有序共晶，但尝试从该类共晶制备聚合物时得到了无序产物。本工作首次报道了共轭三炔的单晶-单晶1,4聚合反应。