Crystal structures and density functional theory calculations of o - And p-nitroaniline derivatives: Combined effect of hydrogen bonding and aromatic interactions on dimerization energy

摘要

The interplay of strong and weak hydrogen bonds, dipole-dipole interactions, and aromatic interactions of o- and p-nitroaniline derivatives was studied by combining crystal structure analysis and density functional theory (DFT) calculations. Crystal structures of four 2-nitroaniline derivatives, 2-((2-nitrophenyl)amino)ethyl methanesulfonate (1A), 2-((2-nitrophenyl)amino) ethyl 4-methylbenzenesulfonate (2A), N,N′-((1,3-phenylenebis(oxy)) bis(ethane-2,1-diyl))bis(2-nitroaniline) (3A), and N-(2-chloroethyl)-2- nitroaniline (4A), and crystal structures of three 4-nitroaniline derivatives, 2-((4-nitrophenyl)amino)ethyl methanesulfonate (1B), 2-((4-nitrophenyl)amino) ethyl 4-methylbenzenesulfonate (2B), and tert-butyl-(2-((4-nitrophenyl)amino) ethyl) carbonate (5B), were analyzed with regard to intra- and intermolecular hydrogen bonding and π-π interactions. The effect of o/p-substitution on π-electron distribution, aromaticity of the nitroaniline ring, and relative strength of intra- and intermolecular weak interactions were compared using HOMA indices, Hirshfeld surfaces, and DFT calculations. The 2-nitroaniline derivatives contain an intramolecular hydrogen bond between amino and nitro groups, creating a six-membered chelate ring, which formed pseudostacked structures with aromatic rings. van der Waals corrected DFT calculations showed that stacking of a phenyl and a chelate ring contributed significantly to the dimerization of 1A and 2A. Therefore, it can be concluded that the phenyl-chelate interactions are an important factor in stacking of the monomers in addition to C-H?O hydrogen bonding. In 4-nitroaniline derivatives, intermolecular N-H?O hydrogen bonds were in a significant role in packing, creating hydrogen-bonded dimers in 1B and 2B, and hydrogen-bonded chains in 5B.