Impact of Aromatic Ring Count on the Ability to Participate in Attractive Interactions. Crystal Structure (X-ray) and Solid State Computational (DFT/QTAIM/RDS/Hirshfeld-surfaces) Study of 1,4-di(2-phenyl-1H-imidazol-4-yl)benzene. A Potential Nanotechnology Intrinsic Component

Abstract

The crystal structure of 1,4-di(2-phenyl-1H-imidazol-4-yl)benzene (DPI4B) is determined by X-ray diffraction with a final R-factor of 6.42% at room temperature. It crystallizes with a space group P2 1 /c, Z = 4, a = 5.01790(10), b = 28.8971(6), and c = 12.9362(3) Å; β = 98.757(2)°. Two 4-phenyl-1H-imidazole (4PI) fragments are related by inversion symmetry and each makes a dihedral angle of 0°with the benzene rings. Despite the presence of a total number of five homo-and heterocyclic rings in the DPI4B molecule, similarly to 2-phenyl-1H-imidazole (2PI) but in contrast to 1,4-di(1H-imidazol-4-yl)benzene (DI4B) and 4-phenyl-1H-imidazole (4PI), it is almost planar. Each plane containing a terminal phenyl ring makes a small dihedral angle of about 3°with the central benzene ring plane. The average twisting angle of the whole molecule is equal to 7°. The ordering of compounds studied according to the decreasing twisting angle is 4PI > DI4B > DPI4B > 2PI and is the same as that according to hydrogen bond length/strength. In DPI4B bereft of N−H···N bonds, four weak C−H···N bonds of C···N = 3.362 Å and ∠(C, H, N) = 158°; C···N = 3.437 Å and ∠(C, H, N) = 123°; C···N = 3.392 Å and ∠(C, H, N) = 128°and C···N = 3.914 Å and ∠(C, H, N) = 156°, force crystalline packing with almost perpendicular adjacent molecules. Strong π···π stacking allows dense packing of planar array of molecules, with a small interlayer distance of 3.413 Å. The analysis of intermolecular interactions pattern supported by quantum theory of atoms in molecules (QTAIM), reduced density gradient (RDS), and Hirshfeld surfaces approach reveals subtle and diverse types of interactions difficult to describe within standard techniques. QTAIM/Hirshfeld clearly indicate the role of interplay between C−H···N hydrogen bonds, N···π and π···π stacking, and a shift from strong (N−H···N) to very weak (C−H···N) attractive interactions supplemented by π···π displaced pure type stacking upon aromatic ring count. QTAIM/RDS reveal mixed attractive/repulsion interactions forcing flatness of the molecule. Electrostatic potential indicates the complementarity of the regions bonded through the C−H···N in the neighboring molecules, which permits easy overcome of any repulsive interactions in DPI4B that may destroy the flatness of the molecule.

Polymorphism and Thermal Stability of Natural Active Ingredients. 3,3′-Diindolylmethane (Chemopreventive and Chemotherapeutic) Studied by a Combined X-ray, 1H–14N NMR-NQR, Differential Scanning Calorimetry, and Solid-State DFT/3D HS/QTAIM/RDS Computational Approach

“…Within this approach the principal components of electric field gradient (EFG) tensor, q ii ( i = x , y , and z ), were obtained after the diagonalization of the traceless tensor. The details of the procedure are published in the previous paper …”

“…Quantum chemical calculations required for QTAIM analysis were carried out within the GAUSSIAN09 code run at WCSS. Theoretical analysis of intermolecular interactions pattern was performed within the Bader’s quantum theory of atoms in molecules (QTAIM) , supplemented with the reduced density gradient (RDG) technique with long-range corrected version of B3LYP using the Coulomb-attenuating method CAM-B3LYP/6-311**G++. − The details of the combined approach are described in ref . Three different approaches to the evaluation of intermolecular potentials were applied.…”

“…The details of the combined approach are described in paper. 58 Three different approaches to the evaluation of intermolecular potentials were applied. According to Espinosa−Molins−Lecomte, 63 the energy of hydrogen bonds was estimated in a simplified manner from the local potential energy density as E H =½V(r BCP ).…”