Molecular and crystal structure of polyclic chainlike compounds - Oxazole and 1,3,4-oxadiazole derivatives: I. Symmetric 2,5-diphenyl-, 2,5-di-2-furyl-, and 2,5-di-2-thienyl-1-3-4-oxidiazoles

The X-ray crystal structures of 2,5-diphenyl-(I), 2,5-di-2-furyl-(II), and 2,5-di-2-thienyl-(III) 1,3,4-oxadiazoles were determined. Crystals I-III are monoclinic. Compound I: a = 5.203(2), b = 18.143(6), and c = 12.184(4) Å; β = 93.24(3)°; V= 1148.3(7) ų; Z = 4 (C₁₄H₁₀N₂O); d_calc = 1.285 g/cm³; sp. gr. P2₁/c. Compound II: a = 5.789(2), b = 10.630(4), and c = 14.911(5) Å; β = 96.44(2)°; V = 911.9(5) ų; Z = 4 (C¹⁰H⁶N²O³); d_calc = 1.473 g/cm³; sp. gr. P2₁/n. Compound III: a = 18.734(7), b = 12.802(3), and c = 8.973(3) Å; β = 101.88(3)°; V = 2105.9(11) ų; Z = 8 (C¹⁰H₆N₂OS₂); d_calc = 1.478 g/cm³; sp. gr. P2₁/c. The angles between the planes of the rings are no larger than 10°. Molecular deformations observed in I-III are due to intermolecular interactions. In crystal, molecules II and III adopt conformations with relative s-trans orientations of the double bonds of adjacent heterocycles.