Crystal structures of the 2:2 complex of 1,1′-(1,2-phenylene)bis(3-m-tolylurea) and tetrabutylammonium chloride or bromide

Abstract

)] (II), both comprise a tetrabutylammonium cation, a halide anion and an ortho-phenylene bis-urea molecule. Each halide ion shows four N-HÁ Á ÁX (X = Cl or Br) interactions with two urea receptor sites of different bis-urea moieties. A crystallographic inversion centre leads to the formation of a 2:2 arrangement of two halide anions and two bis-urea molecules. In the crystals, the dihedral angle between the two urea groups of the bis-urea molecule in (I) [defined by the four N atoms, 165.4 (2) ] is slightly smaller than that in (II) [167.4 (2) ], which is probably due to the smaller ionic radius of chloride compared to bromide. Chemical contextHydrogen bonding, -interactions, anion-interactions, halogen bonds, and anion-macrodipole interactions are some of the crucial principal forces that determine structure, selfassembly and recognition in chemical and biological systems (Lehn, 1990;Jentzsch et al., 2013). Various urea-based anion receptors of varying complexity and sophistication have been designed and prepared (Amendola et al., 2010;Wei et al., 2011; Bregovic et al., 2015). It has been shown that the efficiency of urea to act as a receptor subunit depends on the presence of two parallel polarized N-H fragments, capable of (i) chelating a spherical anion or (ii) donating two parallel hydrogen bonds to the oxygen atoms of a carboxylate or of an inorganic oxoanion (Custelcean, 2013). In our ongoing research on N-rich organic ligand design and synthesis (Wang et al., 2015), we report herein the synthesis of the title orthophenylenediamine based methyl substituted neutral organic bis-urea receptor L and crystal structures of the 2:2 adducts of L with tetrabutylammonium chloride (TBACl) or bromide (TBABr) (I) and (II). Structural commentaryThe molecular structures of the title compounds are illustrated in Figs. 1 and 2. The receptor L displays a trans orientation of two urea groups showing non-cooperativity to each other. In the presence of 1.5 equivalents of tetrabutylammonium chloride or bromide in acetone and Et 2 O the 2:2 host-guest complexes (I) and (II) crystallize in the monoclinic space groups P2 1 /n and P2 1 /c, respectively. The 2:2 adducts are formed via N-HÁ Á ÁX hydrogen bonds between the halide anions and the urea subunits of two bis-urea receptors. Both NH functions of each urea group are trans to the C O double bond across the respective C-N bond, thereby the aromatic substituents are cis, with small C Ar -N-C O torsion angles [C1-N1-C13-O2 = 2.7 (4) and C15-N2-C12-O1 = 11.4 (3) in complex (I), C12-N1-C1-O1 = À0.7 (5) and C14-N3-C13-O2 = 8.5 (4) in complex (II)]. Moreover, it is also evident that the distance between the two terminal aromatic functions varies considerably due to the torsion angles between the two urea groups and between the two phenylene groups. The angles between the planes through the two urea planes are 55.67 (4) and 54.51 (5) in (I) and (II), respectively, with the receptors arranging themselves in a way that in the anion complex the urea groups on the two receptors are o...

Self-Assemblies of Solvates, Ionic Cocrystals, and a Salt Based on 4-{[(4-Nitrophenyl)carbamoyl]amino}-N-(pyrimidin-2-yl)benzene-1-sulfonamide: Study in the Solid and Solution States

“…These obvious distinctions in the bond parameters occurred as a consequence of the differences in the ionic radii of the three halides. For the ionic cocrystals of the tetrabutylammonium halides with urea, ,− oximes suggest the requirement of hydrophobic space to accommodate the cation. , In the present case, the hydrophobic arms of the TBA are positioned in the hydrophobic concave part by the geometrically adjustable angular-shaped host in the assembly held by the C29–H···O interactions.…”

“…The nitrification ability of urea derivatives has been enhanced by sulfa drugs . Some alkaline-earth-metal salts have been used to degrade urea derivatives, , and ionic cocrystals of urea have importance in the study of fertilizer actions. , Generally, charge-assisted hydrogen bonds have energy in the range between 12 and 25 kcal/mol, which provides stability to a halide-assisted assembly. − Due to their electrostatic nature, the charge-assisted hydrogen bonds have higher strengths and such hydrogen bonds are possible in an self-assembly of a urea derivative. , Various urea and related compounds have been used as anion receptors of organic ammonium halides. − Urea derivatives are commonly used to selectively detect fluoride ions over the other halide ions present in a solution. In these processes two issues get priority: one is the solvent, and the other is proton transfer from a chromogenic probe molecule.…”

“…Accordingly, the semirigid urea derivative of a sulfadiazine drug, namely 4-{[(4-nitrophenyl)­carbamoyl]­amino}- N -(pyrimidin-2-yl)­benzene-1-sulfonamide (abbreviated as H3Sulfaurea ; Figure ), has been studied. It has an adjustable tether and also has the potential to form dimeric synthons by utilizing hydrogen bond donor–acceptor properties of the NC–NH group. , On the basis of our earlier studies − on the preparation of a tetrabutylammonium cation barricaded in adjustable spaces formed between self-assembled host molecules, a hydrogen-bonded dimer of H3Sulfaurea would have also the possibility of binding to a halide and accommodating the cation on its folds even when the size of the halide ion varies. With such a design thought, the angular-shaped H3Sulfaurea (Figure ) has been chosen as a host; it has an intervening −SO 2 – group controlling the geometry of the molecule.…”

Visible colorimetric fluoride and hydroxide sensing by asymmetric tris-urea receptors: combined experimental and theoretical studies

“…Very recently, we have reported a symmetry o -phenylendiamine bis-urea with considerable binding strength towards Cl − or Br − . 40 Here, to enrich the library of tris-urea receptors, we would like to report four novel asymmetric tris-urea receptors L1–L4 with the capability of discriminating both fluoride and hydroxide anions ( Scheme 1 ). Compared with mono urea and bis-urea receptors, these receptors with two flexible symmetric urea units (N–H a and N–H b ) and one asymmetric urea unit (N–H c ) contain more H-bond binding sites toward anions.…”