Substituent–π interactions associated with aromatic stacking interactions were experimentally measured using a small N -phenylimide molecular balance model system. The direct interaction of the substituent (NH 2 , CH 3 , OH, F, Br, CF 3 and NO 2 ) with an aromatic ring was measured in the absence of the aromatic stacking interactions in solution. The measured substituent–π energies were found to correlate well with the Hammett σ m parameter similar to the substituent effects observed in aromatic stacking systems. The persistent electrostatic trends in substituent effects can arise from the direct electrostatic interactions between substituents and opposing π-systems. 
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                            Functionalized planar aromatic rings as precursors to energetic N , N ′-(4,6-dinitro-1,3-phenylene)dinitramide and its salts
                        
                    
    
            Functionalization of planar aromatic rings is very straightforward, up scalable, and economical in comparison with many azole, caged, linear or cyclic structures. In our present work, a facile synthesis of N , N ′-(4,6-dinitro-1,3-phenylene)dinitramide (3) is obtained by a single-step nitration of 4,6-dinitrobenzene-1,3-diamine (2). Compound 3 exhibits a surprisingly high density of 1.90 g cm −3 at 100 K (1.87 g cm −3 at 298 K). Its reactions with bases result in the formation of a series of energetic salts (4–7) which exhibit relatively high densities (1.74 to 1.83 g cm −3 ), and acceptable thermal sensitivities (177 to 253 °C). Energetic salt formation increases intermolecular hydrogen bonding while the planarity of the aromatic ring maximizes weak non-covalent interactions (π-stacking, cation/π, anion-π, X-H/π, etc. ,). The synergetic effect of these stabilizing interactions plays a crucial role in increasing thermal stability and decreasing sensitivity toward the external stimuli. Overall, these easily accessible new energetic compounds exhibit high densities and good denotation properties with potential applications as new high-energy materials. 
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                            - Award ID(s):
- 1919565
- PAR ID:
- 10346982
- Date Published:
- Journal Name:
- Materials Chemistry Frontiers
- Volume:
- 6
- Issue:
- 7
- ISSN:
- 2052-1537
- Page Range / eLocation ID:
- 933 to 938
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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