Synthesis, characterisation and crystal structure of a co-crystal of two components:: 1,2-bis(6-methylpyridin-2-yl)ethane-1,2-dione and 1-(pyridin-2-yl)-2-(6-methylpyridin-2-yl)ethane-1,2-dione

A condensation reaction of an equimolar ratio of 2-pyridinecarboxaldehyde and (6-methylpyrid in-2-yl)methanol without a catalyst in a solvent-free reaction at 140 degrees C was expected to yield 2-hydroxy-[1,2-bis(6-methylpyridin-2-yl)]ethan-l-one. FT-IR spectroscopy of the yellow-brown solid reaction product indicated the presence of a - CO - COH - group. The solid compound was treated with cyclohexane and green crystals were produced. The crystals were characterised by FT-IR, H-1 NMR, El mass spectrometry and single-crystal X-ray diffraction. The molecular and crystal structure determined by single-crystal X-ray diffraction resolved one crystal showing two molecular components [C13H10N2O2 and C14H12N2O2] at a ratio of 60.4:39.6 [C13.40H10.79N2O2]. Both compounds co-crystallise in the triclinic space group P-1, with a = 7.859(5), b = 8.021(14), c = 9.060(5) angstrom, alpha = 101.36(2)degrees, beta = 90.06(3)degrees, gamma = 90.92(3)degrees, V = 559.8(5) angstrom(3), Z = 2. The compounds were 1,2-bis(6-methylpyridin-2-yl)ethane-1,2-dione and 1-(pyridin-2-yl)-2(6-methylpyridin-2-yl)ethane-1,2-dione. These results are important because they confirm that condensation in a solvent- and catalyst-free reaction yielded precursors that were converted into alpha-diketone compounds by the action of solvent and oxygen.