Crystal structures of anhydro-bases of 1- and 2-(ethoxycarbonylmethylo)-4-hydroxycinnolinium hydroxides

C₁₂H₁₂N₂O₃,M _r=232.24. (1): C2/c,Z=8,a=14.658(1),b=4.9375(4),c=31.859(4) Å, =91.710(6)°. (2): P2₁/c,Z=4,a=11.422(2),b=4.8864(2),c=21.176(3)Å, =103.29(3)°. The study confirms significant contribution of quinoid diazine ring form in anhydrobase of 1-substituted 4-hydroxycinnolinium hydroxides. The phenomenon corresponds with a negative net charge at formerly positively charged N(1) atom, with fewer hydrogen contacts of less negatively charged O(4) and with increased stacking in 1-substituted derivative, in comparison with 2-substituted structure.