1H-Benzo[g]pteridine-2,4-dione

Abstract

The structure of the title compound, C10H6N4O2, reported by Smalley et al. [(2021). Cryst. Growth Des. 22, 524–534] from powder diffraction data and 15N NMR spectroscopy, is confirmed using low-temperature data from a twinned crystal. The tautomer in the solid state is alloxazine (1H-benzo[g]pteridine-2,4-dione) rather than isoalloxazine (10H-benzo[g]pteridine-2,4-dione). In the extended structure, the molecules form hydrogen-bonded chains propagating in the [0\overline{1}1] direction through alternating centrosymmetric R22(8) rings with pairwise N—H...O interactions and centrosymmetric R22(8) rings with pairwise N—H...N interactions. The crystal chosen for data collection was found to be a non-merohedral twin (180° rotation about [001]) in a 0.446 (4):0.554 (6) domain ratio.

Keywords

• alloxazine
• isoalloxazine
• crystal structure
• tautomerism
• hydrogen bonding