Crystal structure, dissociation and zwitterion formation in 2,6‐diaryl‐1(3)‐oxo‐3(1)‐hydroxy‐5(7)‐imino‐7(5)‐amino‐1 H,5H‐(3‐H,7H)‐pyrazolo[1,2‐a]pyrazoles

Single crystal X‐ray analysis and quaternization of 2,6‐diphenyl‐1(3)‐oxo‐3(1)‐hydroxy‐5(7)‐imino‐7(5)‐1H,‐5H[3H,7H)‐pyrazolo[1,2‐a]pyrazole is described. The dissociation constants are determined and compared with those of 4‐phenyl‐1,2‐dimethyl‐3(5)‐oxo‐5(3)‐hydroxypyrazole and 4‐phenyl‐3,5‐diaminopyrazole. The quaternization of the latter compound is also described. The influence of electron donating substituents at the cationic moiety on the electronic spectra of such paraionic systems is discussed. The title products exist in the solid state as zwitterions and probably as covalent species in solution.