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

The title compound I, C(13)H(10)N(2)O(2)S(2), 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 hydrogen-bonding 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 π–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.