Abstract
The title compound, C25H25N9O9·C16H36N+·H2PO4 - (I) or (C25H25N9O9)·(n-Bu4N+)·(H2PO4 -) (systematic name: 3-(4-nitro-phen-yl)-1,1-bis-{2-[3-(4-nitro-phen-yl)ureido]eth-yl}urea tetra-butyl-ammonium di-hydrogen phosphate), comprises a tris-urea receptor (R), a di-hydrogen phosphate anion and a tetra-n-butyl-ammonium cation. It crystallizes with two independent formula units in the asymmetric unit. The conformations of the two tris-urea receptors are stabilized by N-H⋯O and C-H⋯O intra-molecular hydrogen bonds. Each di-hydrogen phosphate anion has two O-H⋯O inter-molecular hydrogen-bonding inter-actions with the other di-hydrogen phosphate anion. Inversion-related di-anion units are linked by further O-H⋯O hydrogen bonds, forming a chain propagating along the a-axis direction. Each di-hydrogen phosphate anion makes a total of four N-H⋯O(H2PO4 -) hydrogen bonds with two ureido subunits from two different tris-urea receptors, hence each tris-urea receptor provides the two ureido subunits for the encapsulation of the H2PO4 - hydrogen-bonded chain. There are numerous inter-molecular C-H⋯O hydrogen bonds present involving both receptor mol-ecules and the tetra-n-butyl-ammonium cations, so forming a supra-molecular three-dimensional structure. One of the butyl groups and one of the nitro groups are disordered over two positions of equal occupancy.
Highlights
In our ongoing research on nitrogen-rich organic ligands (Wang et al, 2015) and the design and synthesis of ureido receptors (Huang et al, 2017), we report the synthesis of the title trisurea receptor, 3-(4-nitrophenyl)-1,1-bis{2-[3-(4-nitrophenyl)ureido]ethyl}urea (R), based on p-nitrophenyl substituents, and the crystal structure of its complex with tetra-n-butylammonium dihydrogen phosphate
The urea subunits N5/N6 in R1 and N11/N12 in R2 are orientated towards the dihydrogen phosphate ions (P1 and P2) forming a 2:2 adduct via N— HÁ Á ÁO hydrogen bonds with anion P1 and enclosing R22(8) ring motifs (Table 1 and Fig. 1)
Structural commentary The title compound crystallizes with two independent formula units in the asymmetric unit
Summary
Anions play an important role in many chemical, catalysis, environmental and biological systems (Sessler et al, 2006; Vickers & Beer, 2007; Beer & Gale, 2001). Four intramolecular C— HÁ Á ÁO hydrogen bonds are present in receptor R1 and three in R2 (Fig. 1 and Table 1) Both receptors display a cis orientation of the urea subunits (N2/N3 and N5/N6 in R1, and N11/N12 and N14/N15 in R2). The urea subunits N5/N6 in R1 and N11/N12 in R2 are orientated towards the dihydrogen phosphate ions (P1 and P2) forming a 2:2 adduct via N— HÁ Á ÁO hydrogen bonds with anion P1 and enclosing R22(8) ring motifs (Table 1 and Fig. 1). Both NH functions of each urea subunit are trans to the C O group across the respective C— N bond. The dihedral angle between the nitro group and the benzene ring to which it is attached vary, from 7.1 (3) to 13.4 (4) in R1 and from 8.3 (4) to 16.7 (7) in R2
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