The 20 K structure of p-amino-p'-nitrobiphenyl in the non-constraining environment of its β-cyclodextrin inclusion complex

Though p-amino-p'-nitrobiphenyl (PANB) is essentially planar in its crystalline form, it takes on a twisted conformation in its 2:2 crystalline inclusion complex with β-cyclodextrin (β-CD); the angles between the two phenyl rings are 40.6(2) and 42.0(1)°for the two molecules respectively, compared with 44.1(1)°for biphenyl in the gas phase, thus indicating the absence of constraints in the β-CD dimer cage.