V.R. Hathwar

Evaluation of intermolecular interactions in thioisocoumarin derivatives: the role of the sulfur atom in generating packing motifs

Five derivatives of thioisocoumarin bearing aromatic and nonaromatic ring systems have been synthesized and characterized to unravel the importance of interactions due to the presence of a sulfur atom in generating packing motifs in the crystalline state. Apart from the well characterized interactions like C–H⋯S, a CS⋯π interaction is found in one of the case studies. The importance of such interactions in crystal structure packing along with routine C–H⋯π and π⋯π interactions is examined in the context of overall stability in the molecular assembly. The CS⋯π interactions in comparison to CO⋯π interactions have been analyzed using the Cambridge Structural Database (CSD).

3-Butyl-1H-isochromen-1-one

In the title compound, C13H14O2, a derivative of isocoumarin, the packing is stabilized by intermolecular C-H center dot center dot center dot O interactions.

2-Chloro-3-hydroxy-methyl-6-methoxy-quinoline.

All the non-H atoms of the title compound, C11H10ClNO2, are roughly coplanar (r.m.s. deviation = 0.058 Å). In the crystal, adjacent molecules are linked by an O—H⋯N hydrogen bond, generating chains running along the a axis.

2-Chloro-3-hydroxy-methyl-7,8-dimethyl-quinoline.

All non-H atoms of the title compound, C12H12ClNO, are co-planar (r.m.s. deviation = 0.055 Å). The hydroxy H atom is disordered over two positions of equal occupancy. In the crystal, molecules are linked by O—H⋯O hydrogen bonds, generating zigzag chains running along the b axis.

2-Chloro-6-methylquinoline-3-carbaldehyde

The quinolinyl fused-ring of the title compound, C11H8ClNO, is almost planar (r.m.s. deviation = 0.013 Å); the formyl group is slightly bent out of the plane of the fused ring system [C—C—C—O torsion angle = 13.5 (4)°].

3-Phenyl-1-[2-(3-phenyl-isoquinolin-1-yl)-diselan-yl]isoquinoline.

The complete molecule of the title compound, C(30)H(20)N(2)Se(2), is generated by a crystallographic inversion centre at the mid-point of the Se-Se bond. The dihedral angle between the isoquinoline-1-selenol group and the phenyl ring is 14.92 (2)°. The herringbone-like packing of the structure is supported by inter-molecular π-π stacking inter-actions with a shortest perpendicular distance between isoquinoline groups of 3.514 Å; the slippage between these ring systems is 0.972 Å, and the distance between the centroids of the six-membered carbon rings is 3.645 (3) Å.

Topological analysis of electron density and the electrostatic properties of isoniazid: an experimental and theoretical study

Isoniazid (isonicotinohydrazide) is an important first-line antitubercular drug that targets the InhA enzyme which synthesizes the critical component of the mycobacterial cell wall. An experimental charge-density analysis of isoniazid has been performed to understand its structural and electronic properties in the solid state. A high-resolution single-crystal X-ray intensity data has been collected at 90 K. An aspherical multipole refinement was carried out to explore the topological and electrostatic properties of the isoniazid molecule. The experimental results were compared with the theoretical charge-density calculations performed using CRYSTAL09 with the B3LYP/6-31G** method. A topological analysis of the electron density reveals that the Laplacian of electron density of the N-N bond is significantly less negative, which indicates that the charges at the b.c.p. (bond-critical point) of the bond are least accumulated, and so the bond is considered to be weak. As expected, a strong negative electrostatic potential region is present in the vicinity of the O1, N1 and N3 atoms, which are the reactive locations of the molecule. The C-H···N, C-H···O and N-H···N types of intermolecular hydrogen-bonding interactions stabilize the crystal structure. The topological analysis of the electron density on hydrogen bonding shows the strength of intermolecular interactions.

Charge Density Analysis of a Pentaborate Ion in an Ammonium Borate: Toward the Understanding of Topological Features in Borate Minerals

Structural and charge density distribution studies have been carried out on a single crystal data of an ammonium borate, [C(10)H(26)N(4)][B(5)O(6)(OH)(4)](2), synthesized by solvothermal method. Further, the experimentally observed geometry is used for the theoretical charge density calculations using the B3LYP/6-31G** level of theory, and the results are compared with the experimental values. Topological analysis of charge density based on the Atoms in Molecules approach for B-O bonds exhibit mixed covalent/ionic character. Detailed analysis of the hydrogen bonds in the crystal structure in the ammonium borate provides insights into the understanding of the reaction pathways that could result in the formation of borate minerals. The net atomic charges and electrostatic potential isosurfaces also give additional input to evaluate chemical and physical properties in such systems.

2-Chloro­benzo[h]quinoline-3-carbaldehyde

The benzo[h]quinolinyl fused-ring of the title compound, C14H8ClNO, is planar (r.m.s. deviation = 0.016 Å); the formyl group is slightly bent out of the plane [the C—C—C—O torsion angle is 10.7 (4)°].

Intermolecular interactions, charge-density distribution and the electrostatic properties of pyrazinamide anti-TB drug molecule: an experimental and theoretical charge-density study.

An experimental charge-density analysis of pyrazinamide (a first line antitubercular drug) was performed using high-resolution X-ray diffraction data [(sin θ/λ)max = 1.1 Å(-1)] measured at 100 (2) K. The structure was solved by direct methods using SHELXS97 and refined by SHELXL97. The total electron density of the pyrazinamide molecule was modeled using the Hansen-Coppens multipole formalism implemented in the XD software. The topological properties of electron density determined from the experiment were compared with the theoretical results obtained from CRYSTAL09 at the B3LYP/6-31G** level of theory. The crystal structure was stabilized by N-H...N and N-H...O hydrogen bonds, in which the N3-H3B...N1 and N3-H3A...O1 interactions form two types of dimers in the crystal. Hirshfeld surface analysis was carried out to analyze the intermolecular interactions. The fingerprint plot reveals that the N...H and O...H hydrogen-bonding interactions contribute 26.1 and 18.4%, respectively, of the total Hirshfeld surface. The lattice energy of the molecule was calculated using density functional theory (B3LYP) methods with the 6-31G** basis set. The molecular electrostatic potential of the pyrazinamide molecule exhibits extended electronegative regions around O1, N1 and N2. The existence of a negative electrostatic potential (ESP) region just above the upper and lower surfaces of the pyrazine ring confirm the π-electron cloud.