Crystal structure and Hirshfeld surface analysis of 2-methyl-3-nitro-N-[(E)-(5-nitro-thio-phen-2-yl)methyl-idene]aniline.

The title compound, C12H9N3O4S, synthesized by condensation of 5-nitro-thio-phene-2-carbaldehyde and 2-methyl-3-nitro-aniline, crystallizes in the ortho-rhom-bic space group P212121. In the mol-ecule, the aromatic benzene and thio-phene rings are twisted with respect to each other, making a dihedral angle of 23.16 (7)°. In the crystal, mol-ecules are linked by inter-molecular C-H⋯O hydrogen bonds into chains extending along the c-axis direction. Weak π-π stacking inter-actions along the a-axis direction provide additional stabilization of the crystal structure. The roles of the various inter-molecular inter-actions were clarified by Hirshfeld surface analysis, which reveals that the crystal packing is dominated by O⋯H (39%) and H⋯H (21.3%) contacts. The crystal studied was refined as a two-component inversion twin.

Molecular structure and vibrational assignment of melaminium phthalate by density functional theory (DFT) and ab initio Hartree-Fock (HF) calculations.

The molecular geometry, the normal mode frequencies and corresponding vibrational assignment of melaminium phthalate (C3H7N6+.C8H5O4(-)) in the ground state were performed by HF and B3LYP levels of theory using the 6-31G(d) basis set. The optimized bond length numbers with bond angles are in good agreement with the X-ray data. The vibrational spectra of melaminium phthalate which is calculated by HF and B3LYP methods, reproduces vibrational wave numbers with an accuracy which allows reliable vibrational assignments. The title compound has been studied in the 4000-100 cm(-1) region where the theoretical evaluation and assignment of all observed bands were made.