Crystal structure of a host-guest complex of the tris-urea receptor, 3-(4-nitropnenyl)-1,1-bis{2-[3-(4-nitrophenyl)ureido]etbyl}urea, that encapsulates hydrogen-bonded chains of dihydrogen phospnate anions with separate tetra-n-butylammonium counter-ions

The title compound, C25H25N9O9 center dot C16H36N+center dot H2PO4 (I) or (C25H25N9O9)-(n-Bu4N+)center dot(H2PO4-) (systematic name: 3-(4-nitrophenyl)-1,1-bis{2[3-(4-nitrophenyl)ureidolethyllurea tetrabutylammonium dihydrogen phosphate), comprises a tris-urea receptor (R), a dihydrogen phosphate anion and a tetran-butylammonium 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 center dot center dot center dot O and C-H center dot center dot center dot O intramolecular hydrogen bonds. Each dihydrogen phosphate anion has two O-H center dot center dot center dot O intermolecular hydrogenbonding interactions with the other dihydrogen phosphate anion. Inversion-related di-anion units are linked by further O-H center dot center dot center dot O hydrogen bonds, forming a chain propagating along the a-axis direction. Each dihydrogen phosphate anion makes a total of four N -H center dot center dot center dot 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 intermolecular C-H center dot center dot center dot-O hydrogen bonds present involving both receptor molecules and the tetra-nbutylammonium cations, so forming a supramolecular three-dimensional structure. One of the butyl groups and one of the nitro groups are disordered over two positions of equal occupancy.