title: A second tricilinc polymorph of 6,6'-dieth-oxy-2,2'-[propane-1,2-diylbis(nitrilo-methyl-idyne)]diphenol.
abstract: The title Schiff base compound, C(21)H(26)N(2)O(4), is a second triclinic polymorph of a previously reported room-temperature structure [Jia (2009 ▶). Acta Cryst. E65, o646]. Strong intra-molecular O-H⋯N hydrogen bonds generate S(6) ring motifs. Inter-molecular C-H⋯O inter-actions link neighbouring mol-ecules into dimers with an R(2) (2)(16) ring motif. The mean planes of the two benzene rings are almost perpendicular to each other, making a dihedral angle of 88.24 (5)°. An inter-esting feature of the crystal structure is the intermolecular short C⋯O [3.1878 (13) Å] contact which is shorter than the sum of the van der Waals radii of the relevant atoms. The crystal structure is further stabilized by inter-molecular C-H⋯π and π-π inter-actions [centroid-centroid distance = 3.7414 (6) Å]. The structure has a stereogenic centre but the space group is centrosymmetric, so the mol-ecule exists as a racemate.
authors.forename: Hoong-Kun
authors.initials: HK
authors.lastname: Fun
authors.forename: Reza
authors.initials: R
authors.lastname: Kia
authors.forename: Hadi
authors.initials: H
authors.lastname: Kargar
authors.forename: Arezoo
authors.initials: A
authors.lastname: Jamshidvand