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Single-crystal X-ray diffraction (SCXRD) experiments and theoretical calculations based on the Quantum Theory of Atoms in Molecules (QTAIM) approach have been used to analyse the characteristics of the covalent and the non-covalent interactions of 2,4-dinitrodiphenylamine (2,4-dna), also known as Serisol-Yellow 2G. DSC-TGA experiments were also carried out to obtain data on the thermal stability of the entitled compound. SCXRD and QTAIM results showed that 2,4-dna molecules form centrosymmetric dimers linked by unusual O⋯O intermolecular interactions with short contact distances (2.73 A) that are accompanied by C H⋯O and N H⋯O intermolecular interactions. Due to the number of -CH groups available in 2,4-dna, the molecular self-assembly continues through C H⋯O intermolecular interactions, which also contribute with the stabilization of the supramolecular network. The analysis of the ESP map revealed that the most positive region of the -CH groups bound to the most negative -NO2 group forming a R 2 2 ( 7 ) synthon. DSC-TGA analysis revealed that 2,4-dna is stable up to 150 °C.

In this work, we report an analysis of the molecular structure and the hydrogen-bonding patterns in the crystal structures of 5-methoxy-2-nitroaniline (1) and 5-methoxy-2-nitroaniline with 2-amino-5-nitropyridine (1:1) co-crystal (2). X-ray single crystal diffraction experiments were carried out to analyse the intermolecular forces in terms of geometrical criteria. These intermolecular interactions were also investigated through topological analysis of the electron density (ρ) employing QTAIM and NCI methods. Additionally, Raman spectroscopy was employed to analyse the vibrational characteristics of the entitled materials. The supramolecular structure of (1) is produced by crosslinked chains, which are primarily dominated by N-H···O hydrogen bonds. However, C-H···O interactions reinforce this connectivity. Furthermore, the molecules in (1) are connected through two-centre instead of the three-centre hydrogen-bonding interactions between the -NH2 and -NO2 groups commonly observed in nitroanilines. The asymmetric unit of (2) contains two symmetry-independent molecules of 5-methoxy-2-nitroaniline (5M2NA) and two symmetry-independent molecules of 2-amino-5-nitropyridine (2A5NP). The supramolecular structure of (2) is developed not only for N-H···O but also N-H···N and supportive C-H···O hydrogen bonds. The two symmetry-independent 2A5NP molecules bound to each other through two-centre hydrogen bonds between the -NH2 and -NO2 groups forming C 2 2 ( 16 ) chains. 5M2NA molecules bound to these chains forming R 2 2 9 and R 2 2 ( 8 ) synthons. Experimental and theoretical results obtained in this work suggest that C-H···O interactions play an important role in the stabilization of these supramolecular structures.