Topological characterization of electron density, electrostatic potential and intermolecular interactions of 2-nitroimidazole: an experimental and theoretical study

An experimental charge density distribution of 2-nitroimidazole was determined from high-resolution X-ray diffraction and the Hansen-Coppens multipole model. The 2-nitroimidazole compound was crystallized and a high-angle X-ray diffraction intensity data set has been collected at low temperature (110 K). The structure was solved and further, an aspherical multipole model refinement was performed up to octapole level; the results were used to determine the structure, bond topological and electrostatic properties of the molecule. In the crystal, the molecule exhibits a planar structure and forms weak and strong intermolecular hydrogen-bonding interactions with the neighbouring molecules. The Hirshfeld surface of the molecule was plotted, which explores different types of intermolecular interactions and their strength. The topological analysis of electron density at the bond critical points (b.c.p.) of the molecule was performed, from that the electron density rho(bcp)(r) and the Laplacian of electron density del(2) rho(bcp)(r) at the b.c.p.s of the molecule have been determined; these parameters show the charge concentration/depletion of the nitroimidazole bonds in the crystal. The electrostatic parameters like atomic charges and the dipole moment of the molecule were calculated. The electrostatic potential surface of the molecule has been plotted, and it displays a large electronegative region around the nitro group. All the experimental results were compared with the corresponding theoretical calculations performed using CRYSTAL09

Analysis of an unusual hetero-halogen bonded trimer using charge density analysis: A case of concerted type I Br center dot center dot center dot Br and type II Br center dot center dot center dot Cl interactions

The crystal structure of 4-bromo-2-chlorobenzoic acid generates an unusual triangular motif consisting of a hitherto uncharacterized Type I Brai-Br contact along with two Type II Brai-Cl interactions as edges of the triangle. The nature of such bonding is analyzed based on both experimental and theoretical charge density followed by topological analysis

Experimental validation of `pnicogen bonding' in nitrogen by charge density analysis

The participation of a nitrogen atom acting as an electrophile in pnicogen bonding, a hitherto unexplored interaction has been established by experimental charge density analysis. QTAIM and NBO analyses ratify this observation

Structural landscape of benzoic acid: using experimental crystal structures of fluorobenzoic acids as a probe

Experimental crystal structures of mono and polyfluorinated benzoic acids correspond to high energy computed crystal structures of benzoic acid itself, thereby permitting access to its structural landscape

Exploring the rare S-H center dot center dot center dot S hydrogen bond using charge density analysis in isomers of mercaptobenzoic acid

Experimental and theoretical charge density analyses on isomers of mercaptobenzoic acid have been carried out to quantify the hydrogen bonding of the hitherto less explored thiols, to assess the strength of the interactions using the topological features of the electron density. The electron density study offers interesting insights into the nature of the S-H center dot center dot center dot S interaction. The interaction energy is comparable with that of a weak hydrogen bond. The strength and directionality of the S-H center dot center dot center dot S hydrogen bond is demonstrated to be mainly due to the conformation locking potential of the intramolecular S center dot center dot center dot O chalcogen bond in 2-mercaptobenzoic acid and is stronger than in 3-mercaptobenzoic acid, which lacks the intramolecular S center dot center dot center dot O bond. The para-substituted mercaptobenzoic acid depicts a type I S center dot center dot center dot S interaction

Do halogen bonds dictate the packing preferences in solid solutions?

The isomeric compounds, 4-bromo-2-chloro benzoic acid (4Br) and 2-bromo-4-chlorobenzoic acid (2Br), crystallize in entirely different space groups, P2(1)/n and P (1) over bar respectively. Both structures are stabilized by a strong O-H center dot center dot center dot O hydrogen bonds generating a carboxylic acid dimer along with an unusual triangular halogen bonded motif in the former and a well-defined halogen bond in the latter. Charge density analysis establishes the nature of halogen bonds by bringing out significant changes in the packing features of the two structures as well as the quantification of the interaction energies involved in the formation of the motifs. Cocrystallization efforts lead to the formation of solid solutions of varied stoichiometric ratios among the two entirely different crystalline forms, a feature which is observed for the first time, and depends on the nature of the halogen bonds. Despite the significant variations in the charge density distribution in intermolecular space, the triangular motif, with two type II Br center dot center dot center dot Cl and Cl center dot center dot center dot Br and one type I Br center dot center dot center dot Br contact in the structure of 4Br dictates the packing preferences in the solid solution as established by accurate single crystal diffraction studies supported by cognate powder diffraction analysis (PXRD) and differential scanning calorimetric (DSC) studies. A systematic study of the solid solution by varying the stoichiometric ratios establishes the hierarchy in halogen bonded motifs and consequently its directional influence to form the resultant supramolecular assembly

Crystal structure and theoretical charge density studies of dilantin molecule

Dilantin molecule is an inhibitor of multiple protein targets such as prostate-specific antigen, lung cancer cells and it also reduces the tumor growth and invasion of the breast metastatic cancer cells. Understanding the precise geometry, charge density distribution and electrostatic properties of inhibitor pertain to predict the active site interaction between the inhibitor and receptor. Hence, the present study is aimed to determine these parameters through experimental and theoretical studies. Dilantin molecule crystallizes in orthorhombic system with Pna2(1) space group. The crystal and the molecular structure of dilantin molecule has been redetermined using X-ray crystal structure analysis. The two phenyl rings and imidazolidine ring in the molecule are not in coplanar and oriented in different directions, the dihedral angles are 66.6(3) and 65.3(3)degrees. The molecular packing of crystal is stabilized by strong N-H center dot center dot center dot O and weak C-H center dot center dot center dot O intermolecular hydrogen bonding interactions. A theoretical charge density analysis has been performed for the molecule lifted from the crystal, reveals the charge density distribution of dilantin molecule, this result has been compared with the corresponding gas phase studies. The electrostatic properties of the molecule also calculated. The calculated dipole moment of dilantin molecule in the crystal phase is (2.88 D), which is not very much different from its gas phase value (2.68 D). The electrostatic potential map displays strong electronegative regions near the O and N atoms, which are the possible reactive locations of the molecule. (C) 2018 Elsevier B.V. All rights reserved

Experimental evidence for `carbon bonding' in the solid state from charge density analysis

The validity of the newly proposed `carbon bonding', an interaction where a carbon atom acts as an electrophilic site towards a variety of nucleophiles, has been investigated in the solid state. X-ray charge density analysis provides experimental evidence for this hitherto unexplored interaction and unravels its nature and strength

Halogen bonding in fluorine: experimental charge density study on intermolecular F center dot center dot center dot F and F center dot center dot center dot S donor-acceptor contacts

The enigmatic type II C-F center dot center dot center dot F-C and C-F center dot center dot center dot S-C interactions in pentafluorophenyl 2,2'-bithiazole are shown to be realistic ``r-hole'' interactions based on high resolution X-ray charge density analysis

Charge Density Analysis of Ferulic Acid: Robustness of a Trifurcated C-H center dot center dot center dot O Hydrogen Bond

The toplogical features of a sporadic trifurcated C-H center dot center dot center dot O interaction region, where an oxygen atom acts as an acceptor of three weak hydrogen bonds, has been investigated by experimental and theoretical charge density analysis of ferulic acid. The interaction energy of the asymmetric molecular dimer formed by the trifurcated C-H center dot center dot center dot O motif, based on the multipolar model, is shown to be greater than the corresponding asymmetric O-H center dot center dot center dot O dimer in this crystal structure. Further, the hydrogen bond energies associated with these interaction motifs have been estimated from the local kinetic and potential energy densities at the bond critical points. The trends suggest that the interaction energy of the trifurcated C-H center dot center dot center dot O region is comparable to that of a single O-H center dot center dot center dot O hydrogen bond