Zum Einfluß von Lösungsmitteln auf das VIS‐Spektralverhalten von 4′‐Dialkylamino‐α‐cyano‐stilben‐4‐diazoniumsalzen

Abstract

Solvatochromism of 4′‐Dialkylamino‐α‐Cyano‐Stilbene‐4‐Diazonium‐Salts 4′‐Dialkylamino‐stilbene‐4‐diazonium‐salts are deep coloured compounds and give strong solvatochromism. 4′‐Diethylamino‐α‐cyano‐stilbene‐4‐diazonium‐tetrafluoroborate was investigated in 52 different solvents and 3 binary solvent mixtures. With increasing solvent basicity the longest wave lenght absorption maximum (\documentclass{article}\pagestyle{empty}\begin{document}$ \nu^{\hspace{-5pt}\sim}_{\rm max} $\end{document}) decrease. Complex formation by crown ethers causes a decrease of \documentclass{article}\pagestyle{empty}\begin{document}$ \nu^{\hspace{-5pt}\sim}_{\rm max}$\end{document}, too. In solvents with dielectricity constants higher than about 15 dissociation effects superpose solvatochromism. The summary of experimental dates support the approach of specific nucleophilic solvatation of diazonium ions.

Failure of azo coupling by ion pairing of 4′‐Diethylamino‐α‐cyano‐stilbene‐4‐diazonium tetraphenylboranates in water

“…The sodium tetraphenylboranates and the sodium bis(salicy1ato)-borate were prepared according P r e p a r a t i o n of t h e d i a z o n i u m s a l t s . After dissolution of 3,92 g (10 mmole) of the parent amine [15] in a mixture of 100 ml water and 4 ml concentrated hydrochloric acid, 10 ml 1 N solution of sodium nitrite were added dropwise a t 0°C. Then the diazonium salts lb-lf were precipitated by addition of aqueous solutions of the corresponding sodium salts with the complex anion until the reaction mixtures became nearly colourless.…”