The crystal structure of the molecular complex of 2′,6′-dimethoxyflavone with picric acid: Alternating π-stacking and hydrogen-bonding interactions

The title complex is monoclinic with a = 15.100(5), b = 7.624(3), c = 39.997(15) Å, = 99.49(4)°, Z = 8, and space group P2₁/c. There are two geometrically independent, hydrogen-bonded pairs of molecules in the asymmetric part of the structure. Picric acid and 2,6-dimethoxyflavone are held together by hydrogen bonding between the hydrogen of the phenol group and the oxygen of the carbonyl. Additionnally, this hydrogen forms an intramolecular hydrogen bond with the O atom of an ortho-nitro group. Moreover, a stacking interaction is observed between the -benzopyrone portion of the flavone and picric acid.     

On the vacuum states for non-commutative gauge theory

Candidates for renormalizable gauge theory models on Moyal spaces constructed recently have non-trivial vacua. We show that these models support vacuum states that are invariant under both global rotations and symplectic isomorphisms which form a global symmetry group for the action. We compute the explicit expression in position space for these vacuum configurations in two and four dimensions.