Crystal structures of three 4-substituted-2,2′-bipyridines synthesized by Sonogashira and Suzuki–Miyaura cross-coupling reactions

Facile synthetic routes for three 4-substituted 2,2'-bi-pyridine derivatives, 4-[2-(4-methyl-phenyl)-ethyn-yl]-2,2'-bi-pyridine, C19H14N2, (I), 4-[2-(pyridin-3-yl)ethyn-yl]-2,2'-bi-pyridine, C17H11N3, (II), and 4-(indol-4-yl)-2,2'-bi-pyridine, C18H13N3, (III), via Sonogashira and Suzuki-Miyaura cross-coupling reactions, respect-ively, are described. As indicated by X-ray analysis, the 2,2'-bi-pyridine core, the ethyl-ene linkage and the substituents of (I) and (II) are almost planar [dihedral angles between the two ring systems: 8.98 (5) and 9.90 (6)° for the two mol-ecules of (I) in the asymmetric unit and 2.66 (14)° for (II)], allowing π-conjugation. On the contrary, in (III), the indole substituent ring is rotated significantly out of the bi-pyridine plane [dihedral angle = 55.82 (3)°], due to steric hindrance. The crystal packings of (I) and (II) are dominated by π-π inter-actions, resulting in layers of mol-ecules parallel to (30-2) in (I) and columns of mol-ecules along the a axis in (II). The packing of (III) exhibits zigzag chains of mol-ecules along the c axis inter-acting through N-H⋯N hydrogen bonds and π-π inter-actions. The contributions of unknown disordered solvent mol-ecules to the diffraction intensities in (II) were removed with the SQUEEZE [Spek (2015 ▸). Acta Cryst. C71, 9-18] algorithm of PLATON. The given chemical formula and other crystal data do not take into account these solvent mol-ecules.