Non-merohedrally twinned crystals of N,N′-bis (3-methylphenyl)-N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine: An excellent triphenylamine-based hole transporter

N,N′-Bis(3-methylphenyl)-N,N′-diphenyl-l,l′-biphenyl-4, 4′ diamine (TPD), C₃₈H₃₂N₂, crystallizes in the monoclinic space group P2₁ with a pseudo-orthogonal lattice, rather than the previously reported orthorhombic space group P2 ₁2₁i [Kennedy, Smith, Tackley, David, Shankland, Brown & Teat (2002). J. Mater. Chem. 12, 168-172]. The asymmetric unit consists of two independent molecules, A and B, which are arranged along the [100] direction to form vertical layers of alternately stacked A and B molecules. Molecule A shows a great deal of rotational movement in the four terminal aryl rings, resulting in two disordered tolyl groups split over two sites, while molecule B exhibits an almost cis configuration of the two terminal tolyl groups with respect to these ring planes.