Lichtabsorption und Substituenteneffekte bei Stilben‐4‐diazoniumionen

Abstract

Light Absorption and Substituent Effects of Stibene‐4‐diazonium Ions Substituent effects on ṽmax‐values of 31 stilbene‐4‐diazonium ions are studied. With increasing donor strength of a substituent in 4′‐position the long wave absorption band of stibene‐4‐diazonium ions shifts from the ultraviolet to the red region of the spectrum. The particular deep colour of diazonium compounds may be described by the very high σp‐Hammett‐constant of the diazonium group. The substituent effects found characterize stilbene diazonium ions as typical donor‐acceptor chromogenes.

New Red Diazonium Compounds based on 2‐amino benzene diazonium salts

“…The purpose of much earlier work has been a further shift of the spectral sensitivity into the visible region. For substituted fluorene [l, 21, pyrene [3] and stilbene diazonium salts [4] absorption maxima up to about 650 nm were reported. We have analyzed the possibilities to obtain red benzene diazonium salts.…”