Tautomerism, structure in solution and in the solid state of 1:9,5:10-anthradipyrazole.

By means of DFT calculations [B3LYP/6-311++G(d,p), GIAO], the properties of the three tautomers of 1:9,5:10-anthradipyrazole were analyzed and compared with Maspero's crystal structures and NMR results. The agreement is fairly good and in agreement with indazole tautomers. Besides, the aromaticity of these interesting five-membered ring systems was explored. [ABSTRACT FROM AUTHOR]