Structure and crystal packing of 4-aminobenzonitriles and 4-amino-3,5-dimethylbenzonitriles at various temperatures

Redetermination of the structure of 4-amino-benzonitrile, C7H6N2

“…The cell constants determined are in good agreement with the ones reported for the monoclinic polymorph at room temperature [5]. Thus, the phase transition that was reported to take place between room temperature and 255 K [6] could not be observed in our diffraction study. At the moment we suggest that the fast cooling to 200 K preserves the monoclinic room temperature phase.…”

“…The smallest angle was detected on the carbon atom bearing the amino group. The trend in both these values is identical with the ones found for the monoclinic as well as the orthorhombic polymorph [5,6]. Due to resonance with the aromatic system, the amino group shows planarization.…”

“…of all fitted atoms = 0.0259 Å). The planes defined by the respective atoms of the amino/imino group on the one hand as well as the phenyl group on the other hand enclose an angle of 11(2)°-a value that is slightly smaller than observed for the room temperature monoclinic polymorph [5] and as determined by NQR spectroscopy [7] and less than one third of the value observed for the low temperature orthorhombic polymorph [6]. In the crystal, classical hydrogen bonds of the N-H···N type are observed next to C-H···N contacts whose range falls by nearly 0.2 Å below the sum of van-der-Waals radii of the atoms participating in them.…”

“…Both -amines and some of their salts -were found to be excellent bactericides, fungicides and algaecides, and research about aromatic amines was further motivated by the presence of such amines in natural products, sulpha drugs, vitamins, amino acids and nucleic acids [4]. The structure of the title compound has been determined twice already, once at ambient temperature [5] and once at low temperature (153 K) [6]. The latter study reported a solid-solid phase transition for the title compound upon cooling the sample from 293 K to 255 K that turned the monoclinic into an orthorhombic polymorph.…”

Picosecond X-Ray Diffraction Probed Transient Structural Changes in Organic Solids

“…The parameters of p1 were determined by the [ refinement of the t i , 0 structures. p1 is essentially the heated ground state structure [13,18]. The t i .…”