Derivatives of Δ2-pyrazoline-products of 1,5-diaminotetrazole interaction with chalcone: Molecular structure and spectral properties

1,5-diaminotetrazole at conditions of its interaction with chalcones (1,3-diphenylpropenones) in hot DMF undergoes Dimroth rearrangement to 5-tetrazolylhydrazine, which results in formation of 1-(5-tetrazolyl)-3,5-diaryl-Δ2-pyrazolines (I). Structure of the obtained products was confirmed by their parallel synthesis and X-ray structural analysis. Unusual fluorescence behavior of the tetrazolopyrazolynes in polar solvents was attributed to the dissociation of their highly acidic tetrazole N–H group. The last hypothesis was confirmed at the investigation of the protolytic interactions of I with tertiary amine.