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

The title compound, C(25)H(25)N(9)O(9)·C(16)H(36)N(+)·H(2)PO(4) (−) (I) or (C(25)H(25)N(9)O(9))·(n-Bu(4)N(+))·(H(2)PO(4) (−)) (systematic name: 3-(4-nitro­phen­yl)-1,1-bis­{2-[3-(4-nitro­phen­yl)ureido]eth­yl}urea tetra­butyl­ammonium di­hydrogen phosphate), comprises a tris-urea receptor (R), a di­hydrogen phosphate anion and a tetra-n-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⋯O and C—H⋯O intra­molecular hydrogen bonds. Each di­hydrogen phosphate anion has two O—H⋯O inter­molecular hydrogen-bonding inter­actions with the other di­hydrogen 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 di­hydrogen phosphate anion makes a total of four N—H⋯O(H(2)PO(4) (−)) 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 H(2)PO(4) (−) hydrogen-bonded chain. There are numerous inter­molecular C—H⋯O hydrogen bonds present involving both receptor mol­ecules and the tetra-n-butyl­ammonium 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.