Diacetylenes with Ionic-Liquid-Like Substituents: Associating a Polymerizing Cation with a Polymerizing Anion in a Single Precursor for the Synthesis of N-Doped Carbon Materials

• Published in: Chemistry : a European journal Vol. 22; no. 5; pp. 1682 - 1695
• Main Authors: Fahsi, Karim, Dumail, Xavier, Dutremez, Sylvain G., van der Lee, Arie, Vioux, André, Viau , Lydie
• Format: Journal Article
• Language: English
• Published: WEINHEIM Blackwell Publishing Ltd 26.01.2016; Wiley; Wiley Subscription Services, Inc; Wiley-VCH Verlag
• Subjects: Adsorption; alkynes; Anions; Argon; azolium compounds; Carbon; Cationic polymerization; Chemical Sciences; Chemical synthesis; Chemistry; Chemistry, Multidisciplinary; Conductivity; Construction; Crystallography; cyanides; Electrical conductivity; Electrical resistivity; Graphite; Graphitization; Heating; Ionic liquids; Krypton; Material chemistry; Maximization; Nitrogen; nitrogen doping; Optimization; Physical Sciences; Polydiacetylenes; Polymerization; Precursors; Pyrolysis; Resistivity; Science & Technology; Spectroscopy; Temperature effects; POLYYNES; alkynes; cyanides; REACTIVITY; CRYSTAL-STRUCTURES; GRAPHITE; SALTS; nitrogen doping; SOLID-STATE; azolium compounds; SPECTROSCOPY; carbon; NITROGEN; DERIVATIVES; CYCLOAROMATIZATION
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201502181

Imidazolium‐ and benzimidazolium‐substituted diacetylenes with bromide or nitrogen‐rich dicyanamide and tricyanomethanide anions were synthesized and used as precursors for the preparation of N‐doped carbon materials. On pyrolysis under argon at 800 °C both halide precursors afforded graphite‐like structures with nitrogen contents of about 8.5 %. When the dicyanamide and tricyanomethanide precursors were thermolyzed at the same temperature, graphite‐like structures were obtained that exhibit nitrogen contents in the range 17–20 wt %; thereby, the benefit of associating a polymerizing cation with a polymerizing anion in a single precursor was demonstrated. On pyrolysis at 1100 °C the nitrogen contents of the latter pyrolysates remain high (ca. 6 wt %). Adsorption measurements with krypton at 77 K indicated that the materials are nonporous. The highest electrical conductivity was observed for a pyrolysate with one of the lowest nitrogen contents, which also has the highest degree of graphitization. Thus, the quest for N‐rich carbons with high electrical conductivities should include both maximization of the nitrogen content and optimization of the degree of graphitization. Crystallographic investigation of the precursors and spectroscopic characterization of the pyrolysates prepared by heating at 220 °C indicate that construction of the final carbon framework does not involve the intermediate formation of a polydiacetylene. N‐riched carbon: Azolium‐substituted diacetylenic compounds with nitrogen‐rich dicyanamide and tricyanomethanide anions undergo concomitant trimerization of the anions and polycyclization of the diacetylenic units to produce graphite‐like carbon materials (see figure). Nitrogen contents reach 17–20 wt % at 800 °C and remain as high as about 6 wt % at 1100 °C.