Abstract
The title compounds, tetra-butyl-ammonium chloride-1,1'-(1,2-phenyl-ene)bis-(3-m-tolyl-urea) (1/1), C16H36N+·Cl-·C22H22N4O2 or [(n-Bu4N+·Cl-)(C22H22N4O2)] (I) and tetra-butyl-ammonium bromide-1,1'-(1,2-phenyl-ene)bis-(3-m-tolyl-urea) (1/1), C16H36N+·Br-·C22H22N4O2 or [(n-Bu4N+·Br-)(C22H22N4O2)] (II), both comprise a tetra-butyl-ammonium cation, a halide anion and an ortho-phenyl-ene bis-urea mol-ecule. Each halide ion shows four N-H⋯X (X = Cl or Br) inter-actions 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 mol-ecules. In the crystals, the dihedral angle between the two urea groups of the bis-urea mol-ecule 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.
Highlights
(1/1), C16H36N+BrC22H22N4O2 or [(n-Bu4N+Br)(C22H22N4O2)] (II), both comprise a tetrabutylammonium cation, a halide anion and an ortho-phenylene bis-urea molecule
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 the synthesis of the title orthophenylenediamine based methyl substituted neutral organic bis-urea receptor L and crystal structures of the 2:2 adducts of
Summary
Hydrogen 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 the synthesis of the title orthophenylenediamine based methyl substituted neutral organic bis-urea receptor L and crystal structures of the 2:2 adducts of. The molecular structure of (I), with atom labels and 50% probability displacement ellipsoids for non-H atoms
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