Preparation and characterization of N-benzyl-2-methyl-4-nitroaniline (BNA) single crystals by physical vapour transport (PVT) technique

Abstract

Good quality of N-benzyl-2-methyl-4-nitroaniline (BNA) single crystals (space group Pna21, point group mm2) having different morphologies were successfully grown from vapour phase for the first time by physical vapour transport technique under predefined supersaturation conditions. BNA single crystals of different morphologies resulted at different supersaturation conditions: prismatic (σ = 0.0218 to 0.1553), columnar (σ = 0.1553 to 0.4652), needle (σ = 0.4652 to 0.7245), fine-needle (σ = 0.7245 to 0.9166) and dendritic (σ = 0.9166 to 0.9729). The predicted theoretical morphologies using BFDH, and attachment energy models are in line with the experimental morphologies. The slice thickness, slice energy, attachment energy and anisotropic growth factor of different faces were determined which reveals that {020} are the slow-growing and morphologically important facets amongst others present in the grown BNA single crystal. Fast growth along ‘+c’ direction and no growth along ‘-c’ direction was identified due to the supersaturation-dependant anisotropic growth nature of BNA. Crystal purity and quality are confirmed by single crystal X-ray diffraction study. In addition, the role of intermolecular interactions, electrostatic, polarization, repulsion and dispersion energy components involved in the crystal packing to stabilize the BNA single crystal were characterized by the Crystal Explorer 17.5 software. Computed energy frameworks confirm that the dispersion energy component is predominantly contributing to the crystal packing than the Coulombic interaction energies.