Biphenyl-4,4'-diyl bis-(2,2,5,5-tetra-methyl-1-oxyl-3-pyrroline-3-carboxyl-ate).

In the title compound, C(30)H(34)N(2)O(6), the complete molecule is generated by a crystallographic 2/m symmetry operation. The 1-oxyl-3-pyrroline-3-carboxyl-ate group lies on a mirror plane. The dihedral angle between the ring planes of the biphenyl fragment is constrained by symmetry to be zero, resulting in rather short intramolecular H⋯H contact distances of 2.02 Å. In the crystal, molecules are connected along the a-axis direction by very weak intermolecular methyl-phenyl C-H⋯π interactions. The C-H bond is not directed to the center of the benzene ring, but mainly to one C atom [C-H⋯C(x - 1, y, z): H⋯C = 2.91 Å and C-H⋯C = 143°].