Di- and triindolylmethanes: molecular structures and spectroscopic characterization of potentially bidentate and tridentate ligands

4-Bromophenyldi(3-methylindol-2-yl)methane (2) and 2-methoxyphenyldi(3-methylindol-2-yl)methane (3) were prepared by sulfuric-acid-catalyzed reactions of 3-methylindole with 4-bromobenzaldehyde and o-anisaldehyde, respectively. Di(3-methylindol-2-yl)phenylmethane (1) and tri(3-methylindol-2-yl)methane (4) were similarly prepared as described previously. Spectroscopic data (¹H, ¹³C NMR) and the X-ray crystal structures for 1 C₂H₅OH and 2–4 are reported. The molecular structure of 1 C₂H₅OH shows hydrogen bonding of both indolyl NH protons to the oxygen of an ethanol molecule. Crystal data for 1 C₂H₅OH: Orthorhombic, Pca2₁, a = 23.9782(17) Å, b = 8.4437(7) Å, c = 11.3029(9) Å, V = 2288.4(3) ų, R ₁ = 0.0597. Crystal data for 2: Orthorhombic, P2₁2₁2₁, a = 8.911(3) Å, b = 9.584(4) Å, c = 24.040(11) Å, V = 2053.0(14) ų, R ₁ = 0.0454. Crystal data for 3: Monoclinic, P2₁/c, a = 9.737(2) Å, b = 25.035(6) Å, c = 9.359(2) Å, = 114.853(4), V = 2070.2(8) ų, R ₁ = 0.0511. Crystal data for 4: Trigonal, R3, a = 14.2214(10) Å, c = 9.6190(10) Å, V = 1684.8(2) ų, R ₁ = 0.0425.