Single Crystal to Single Crystal Polymerization of a Self-Assembled Diacetylene Macrocycle Affords Columnar Polydiacetylenes

This manuscript describes a single-crystal-to-single-crystal polymerization of the dihydrate of diacetylene <b>1</b> (<b>1</b>·2H₂O) to give an unusual polydiacetylene (PDA) structure that consists of aligned nanotubes, with each covalently bonded nanotube having two parallel PDA chains that run parallel down opposite sides of a channel defined by the macrocycle. Each PDA nanotube is connected with four other columns via amide hydrogen bonds with an N-(H)···O distance of 2.888(4) Å. Such well-ordered polymers should display quasi-one-dimensional electronic structures and may be of interest for the formation of highly conductive organic materials. We obtained the <b>1</b>·2H₂O form in bulk, which was polymerized by heating. Powder X-ray diffraction suggests that bulk PDA powder is single phase and displays a similar structure as the PDA single crystals. Furthermore, we showed that PDA crystals absorbed I₂ vapor. We believe that this unique PDA structure, which is amenable to property control via adsorbed guests, will be an attractive one for investigating charge-transfer doping in PDA-based organic electronic materials. We also observed two additional crystal forms, including <b>1</b>·MeOH, which also shows a columnar assembly, and a tetrahydrate <b>1</b>·4H₂O that shows water tetramers that link four cycles into a 2D sheet structure