Synthesis of aromatic polynitroso compounds: Towards functional azodioxy-linked porous polymers

The polymerization property of aromatic polynitroso compounds could be used to create azodioxy porous networks with possible application for the adsorption of CO₂, the main greenhouse gas. Herein, we report the synthesis and characterization of new aromatic polynitroso compounds, with para-nitroso groups attached to the triphenylbenzene, triphenylpyridine, triphenyltriazine and triphenylamine moiety. The synthesis of the pyridine-based trinitroso compound was performed by reduction of the corresponding trinitro derivative to N-arylhydroxylamine followed by oxidation to the trinitroso product. For the synthesis of the benzene- and triazine-based trinitroso compounds, a novel synthetic strategy was implemented, which included cyclotrimerization of the 4-nitrosoacetophenone and 4-nitrosobenzonitrile, respectively. Reduction of the trinitro compound with triphenylamine unit produced the dinitroso product. In a solid state, all synthesized compounds form E-azodioxy oligomers or polymers. While azodioxy polymer with triphenylbenzene moiety is an amorphous solid, other azodioxy oligomers and polymers displayed sharp diffraction peaks pointing to their crystalline nature. A computational study indicated that eclipsed AA configurations are preferred over staggered AB and inclined AA' configurations. The serrated layers may be the most likely outcome when/if 2D layers form an organized polymer network of azodioxy linked triphenyltriazine-based building blocks.