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Synthesis and characterization of aromatic trinitroso compounds – potential building blocks for new porous organic polymers

Porous organic polymers (POPs) incorporating nitrogen-rich functionalities have emerged as promising materials for efficient and highly selective CO2 capture and separation. We recently reported synthesis and characterization of new two-dimensional (2D) benzene- and triazinebased azo-bridged POPs and identified potential candidates for selective CO2 adsorption. In the continuation of our work on design and synthesis of promising building blocks for formation of new POPs we focused on the compounds with multiple aromatic C-nitroso groups. It is known that the simplest such compound, 1, 4-dinitrosobenzene, forms remarkably stable 1D azodioxy polymer which could be possibly used as organic semiconductor, while polymerization of monomers with tetrahedrally oriented nitroso groups leads to formation of porous three-dimensional (3D) diamondoid azodioxy networks. In this work, we report the synthesis and characterization of novel aromatic trinitroso compounds and their potential application for the creation of polymeric azodioxy networks. The selected starting compounds (Fig. 1) contain three phenyl rings with a nitroso group in the para-position attached to the different central unit: benzene (1a), pyridine (1b), triazine (1c) and nitrogen atom (2). Bearing in mind that preparation of aromatic C-nitroso compounds is not simple, different synthetic methods were tested. The prepared compounds were characterized by IR spectroscopy, solution- and solid-state NMR spectroscopy, powder X-ray diffraction and thermogravimetric analysis. The obtained results indicate the formation of oligomers or polymers that contain E-azodioxy linkages and show good thermal stability. Preliminary computational study based on the calculation of binding energies and analysis of the electrostatic potential maps allowed us to locate the best binding sites with CO2 molecules.

Porous organic polymers ; Aromatic trinitroso compounds ; CO2 adsorption

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