Dicyanmethylenpyrazolinone und deren Bedeutung als Chromophor. Synthesen mit Nitrilen, 80. Mitt.

1-Phenyl-2-pyrazolin-5-ones1 a–e react with tetracyanoethylene forming the corresponding dicyanomethylenepyrazolin-5-ones2 a–e. The products are deeply coloured with absorption bands between 550 and 650 nm, but low -values and negative solvatochromic effect. By amine-HCN exchange reaction with anilines the red-coloured phenylamino-cyanomethylene-pyrazolinones3–6 are obtained.¹⁵N- and¹³C-NMR-data of2 and quantum-chemical calculations (INDO/S-CI) reveal the extreme polarization and chromophoric properties of the described dicyanomethylene-pyrazolinones.