Conformational polymorphs and solid-state polymerization of 9-(1,3-butadiynyl)carbazole derivatives

• Novel two diacetylenes carrying a carbazole group were prepared and characterized by crystallographic analyses.
• Two polymorphs were discovered, one of which showed reactivity for solid state polymerization of diacetylenes.
• Both diacetylene derivatives gave polydiacetylenes by thermal annealing whose absorption bands extended to near IR region.

The novel diacetylenes, 9-(5-(4-nitrophenoxy)penta-1,3-diyn-1-yl)-9H-carbazole (1) and 4-((5-(9H-carbazol-9-yl)penta-2,4-diyn-1-yl)oxy)benzonitrile (2), were prepared and characterized by crystallographic analyses. Compound 1 gave two conformational polymorphs, 1-(I) and 1-(II), whose differences were concluded to originate in intermolecular interactions among nitrophenyl groups. Crystal 1-(I) and 2 had suitable molecular arrangements for solid-state polymerization and polymerized by thermal annealing to give crystalline polydiacetylenes (PDAs). While an arrangement of 1-(II) was unsuitable for the polymerization. The PDAs showed broad absorption from UV to near IR region (ca. 900 nm), suggesting effective expansion of π-conjugated system by carbazolyl groups.