Ice-like Cyclic Water Hexamer Trapped within a Halide Encapsulated Hexameric Neutral Receptor Core: First Crystallographic Evidence of a Water Cluster Confined within a Receptor-Anion Capsular Assembly

Abstract

Over the past few decades, the tren [tris(2-aminoethyl)amine] skeleton has materialized as one of the supreme anion binding building blocks demonstrating a strong interplay among topology, complementarity, cooperativity, and coordination. However, anion recognition by modest tren-based unsubstituted aromatic urea has been underexplored, mainly due to the deficiency of π-acidic or electronwithdrawing aryl terminals. This report establishes an infrequent hexameric neutral receptor-anion-water molecular self-assembly, where a conformationally flexible C 3v -symmetric halide (F − /Cl − ) encapsulated electron-rich naphthyl group containing N-bridged tripodal urea receptor effectively entraps a chair-shaped ice-like neutral cyclic water hexamer within the hexameric cavity of a neutral receptor-halide host−guest assembly.

Self-Assemblies of Positional Isomeric Linear Bis-Urea Ligands with Oxyanions/Hydrated Oxyanions: Evidence of F– and OH– Induced Atmospheric CO2 Fixation

“…Continuing our group’s pursuit in the field of substituent driven anionic/hydrated anionic supramolecular self-assemblies of acyclic receptors, − herein we develop a class of nitro-phenyl functionalized comparatively less cooperative and more challenging positional isomeric linear bis-urea receptors L 1 – L 3 (Scheme ), derived from the least converging aromatic diamine ( para -phenylenediamine) to investigate the coordination behavior with anions/hydrated anions in neutral form. Structural studies reveal that both para -isomer ( L 1 ) and meta -isomer ( L 1 ) are capable of (HCO 3 ) 2 -dimer entrapment either by fluoride or hydroxide induced fixation of atmospheric CO 2 in complexes 1a , 2a , and 2b .…”

Intermolecular Interactions in Functional Crystalline Materials: From Data to Knowledge

“…Analysis of crystal packing in pharmaceuticals, their homologues, polymorphs, co-crystals, and solvates gives one information about preferable synthons that could appear in a binding pocket occupied with this drug (although some weak interactions can be over-, or under-estimated). Data knowledge about typical water associates in crystals of small molecules is important for biochemistry as similar hydrate architectures were found in crystals of inorganic, organic, and macromolecular compounds [40,41].…”

“…Analysis of solvate connectivity and the most abundant motifs (if any) formed by solvent molecules is similar to that described above for the investigation of other synthons and supramolecular associates. The practical meaning of results obtained for material chemistry, biochemistry, and the pharmaceutical industry are based on the fact that similar hydrate architectures were found in crystals of both inorganic, organic, coordination, and even macromolecular compounds [40,41]. H-bonding between a complex and an outer sphere solvent can lead to additional quenching in luminescent materials that are unfavorable for the task-specific design of optical materials [283,284].…”

Terminal Substituent Induced Differential Anion Coordination and Self-Assembly: Case Study of Flexible Linear Bis-Urea Receptors

“…In biomineralized materials surrounded by planar oxyanions, one of the major components is carbonate, in particular working as a buffer in blood and the exoskeletons of radiolaria, where in the form of acetyl coenzyme A acetate anion, it is exploited by the organisms. , Due to the increased ingestion of fossil fuels by automobiles, industries, etc. that is the foremost cause of a major rise in atmospheric CO 2 concentration , there is a demand for the effectual activation and fixation of atmospheric CO 2 into green chemicals. − Up to now, several structurally preorganized neutral or protonated anion receptors having a tripodal cavity with various −NH functionalities have been approved. − In the literature, in comparison to tripodal receptors the use of dipodal receptors toward anion recognition is common, as the dipodal receptor scaffolds are comprised of a smaller number of coordination sites and also exhibit less flexibility and more rigidity. Nevertheless, few dipodal anion receptors having urea/thiourea functionalization resulting from preorganized diamine over isomeric aromatic diamines have been reported in the literature by different groups − and also by our group. , …”