The supramolecular effect of aromaticity on the crystal packing of furan/thiophene carboxamide compounds

Abstract

N-2-pyrazinyl-2-furancarboxamide (I) and N-2-pyrazinyl-2-thiophenecarboxamide (II) are compounds containing different five-membered heteroaromatic rings, furan and thiophene, respectively. They were designed and synthesized to examine the effect of an increase in aromaticity from furan to thiophene on the crystal packing. In order to explore the various features of the crystal packing motifs in more detail, single crystal X-ray diffraction, Hirshfeld surface analysis and theoretical calculations were carried out on the two compounds. The results clearly show that the heteroatom substitution of O to S in five-membered rings led to an increase in the effectiveness of π-based interactions in II, whereas hydrogen bond interactions play a more important role in the stabilization of the supramolecular architecture of I.

Self-Assembly of Fluorinated Boronic Esters and 4,4′-Bipyridine into 2:1 N→B Adducts and Inclusion of Aromatic Guest Molecules in the Solid State: Application for the Separation of o,m,p-Xylene

“…From a crystal engineering point of view, the molecular structures of A1 – A5 are susceptible to a series of intermolecular interactions including π···π, C–H···O, and C–H···π contacts and, for the fluorine derivatives A2 – A5 , additionally C–H···F and F···F contacts. − It can be expected that the presence of electron-deficient ( bpy coordinated to boron atoms) and electron-rich aromatic substituents (cat and B-aryl) facilitate the formation of strong π···π interactions, which will likely dominate the supramolecular solid-state organization. The importance of π···π interactions for the structural organization of molecular crystals and MOFs is a topic of current interest in crystal engineering. ,− In this context, the crystal structure analysis of the fluorine-free boronic ester adduct A1 reveals the presence of π···π contacts involving the N→B coordinated bpy groups and the B-phenyl substituents of two neighboring adduct molecules with centroid···centroid distances of 3.87 Å. The formation of π···π contacts between the electron-deficient bpy linkers and the B-phenyl group and not the catecholate moieties is somewhat surprising, because DFT calculations on catechol esters of fluorinated arylboronic acids at the RB3LYP/6-311G­(2df,p) level have shown that the HOMO orbitals appear over the boron atom and the B-catecholate fragment …”

“…The crystallographic analysis of A1 – A5 revealed that π-stacking constitutes an essential element in most of the crystal structures. From the vast literature on π···π interactions, − it is well-known that π···π contacts between electron-deficient and electron-rich aromatic species are particularly strong and frequently accompanied by electron transfer. In order to analyze the potential of the N→B adducts described herein for complex formation, the molecular electrostatic potential (ESP) surface map of A3 and a series of aromatic guest molecules was calculated (i.e., benzene, toluene, o -xylene, m -xylene, p -xylene, mesitylene, naphthalene, aniline, 1-naphthol, 3-bromophenol, tetrathiafulvalene, and benzonitrile).…”

Resonance-Assisted Hydrogen Bonding and π–π Stacking Modulates the Charge Transfer Coupling in Crystalline Naphthothiazoles

“…In addition, aromaticity can be employed in the framework of crystal engineering to design efficient supramolecular synthons. , [Anti]­aromaticity gain or loss was found to modulate the strength of hydrogen bonds, enhance charge transport behavior in n-type nonaromatic organic dyes upon forming HB, enable conductivity in electronic devices, and enhance the basicity of organic superbases . The study of charge transport properties in DNA base pair stacks has gained considerable attention in the scientific community. − Exploring continuous π–π stacked hydrogen-bonded chromophoric assemblies mimicking the nonhelical structure of DNA base-pair stacks − could beget intriguing charge transport properties.…”

Synthesis and Photocatalytic Properties of Four Coordination Compounds Constructed from Two Benzimidazole-Based Asymmetric Polyazocyclic Ligands

“…In recent years, coordination compounds as an emerging material for photocatalysis have been widely used in water treatment and recycling fields [11][12][13][14][15]. The benzimidazole ligands are usually used as N-donor ligands, which can adopt different conformations according to the coordination geometry requirements of different metal ions, and serve as donors and acceptors of hydrogen bonds [16][17][18][19][20][21].…”