From Linear Molecular Chains to Extended Polycyclic Networks: Polymerization of Dicyanoacetylene

5 years ago

From Linear Molecular Chains to Extended Polycyclic Networks: Polymerization of Dicyanoacetylene

Timothy A. Strobel, Huiyang Gou, Albert Epshteyn, Derek W. Keefer, Duck Young Kim, Liuxiang Yang, Jordan Lerach, Clemens Prescher, Haw-Tyng Huang, Matthew D. Ward, Arani Biswas, John V. Badding, Shengnan Wang, Li Zhu, Artem R. Oganov, Brian L. Chaloux

Dicyanoacetylene (C₄N₂) is an unusual energetic molecule with alternating triple and single bonds (think miniature, nitrogen-capped carbyne), which represents an interesting starting point for the transformation into extended carbon–nitrogen solids. While pressure-induced polymerization has been documented for a wide variety of related molecular solids, precise mechanistic details of reaction pathways are often poorly understood and the characterization of recovered products is typically incomplete. Here, we study the high-pressure behavior of C₄N₂ and demonstrate polymerization into a disordered carbon–nitrogen network that is recoverable to ambient conditions. The reaction proceeds via activation of linear molecules into buckled molecular chains, which spontaneously assemble into a polycyclic network that lacks long-range order. The recovered product was characterized using a variety of optical spectroscopies, X-ray methods, and theoretical simulations and is described as a predominately sp² network comprising “pyrrolic” and “pyridinic” rings with an overall tendency toward a two-dimensional structure. This understanding offers valuable mechanistic insights into design guidelines for next-generation carbon nitride materials with unique structures and compositions.

Publisher URL: http://dx.doi.org/10.1021/acs.chemmater.7b01446

DOI: 10.1021/acs.chemmater.7b01446