Crystal structure of 1-ethyl-3-(2-oxo-1,3-dithiol-4-yl)quinoxalin-2(1H)-one.

The title compound I, C₁₃H₁₀N₂O₂S₂, crystallizes in the monoclinic space group C2/c with eight molecules in the unit cell. Excluding for the ethyl substituent, the molecule of I adopts a nearly coplanar conformation (r.m.s. deviations is 0.058 Å), which is supported by the intramolecular C-H...O hydrogenbonding interaction between the two ring systems [C...O = 2.859 (3) Å]. In the crystal, the molecules form dimeric associates via two bifurcated C-H...O hydrogen-bonding interactions between an ene hydrogen atom and a carbonyl functional group of an adjacent molecule [C...O = 3.133 (3) Å] and vice versa. The crystal structure is further stabilized by a three-dimensional network of weak hydrogen bonds between one molecule and six adjacent molecules as well as offset &#960-π stacking. The combination of the quinoxaline 2(1H)-one moiety with the dithiocarbonate moiety extends the aromaticity of the quinoxaline scaffold towards the substituent as well as influencing the π-system of the quinoxaline. The title compound is the direct precursor for a dithiolene ligand mimicking the natural cofactor ligand molybdopterin. [ABSTRACT FROM AUTHOR]