24,26-Dioxo-3,6,14,17-tetraazapentacyclo((21.0.1(1,19).1(3,6) .1 (8,12) .1(14,17))hexacosan-1(23),8(25),9,11,19,21-hexaene, C22H24N4 O (2) , FW=376.45, monoclinic,P2(1) /n,a=11.144(2) Angstrom, b=6.395(1) Angstrom, c=13.562(3) Angstrom, beta=95.81(1)degrees, V=961.5(3) Angstrom 3 , Z=2, D col =1.300 Mg/m(3) , mu=0.685 mm(-1) , F(000)=400, lambda (CuKalpha)=1.5418 Angstrom final R1 and wR2 are 0.0409 and 0.1547, respectively. The macro ligand consists of two phenyl rings and two five-membered rings forming the walls of the central cavity which has roughly a square cross-section. The orientation of the phenyl ring is antiperiplanar and approximately perpendicular to the diazacyclopentanone ring which adopts envelope conformation. The molecules are stabilized by C-H...O and C-H...pi types of intermolecular interactions in addition to van der Waals forces.