Über zweistufige Redoxsysteme, XIX. UV/VIS‐Spektroskopie vinyloger und azavinyloger Redoxsysteme mit 1,3,3‐Trimethylindolenin als Endgruppe sowie eine Farbregel für Violene

Abstract

Two-step Redox Systems, XIXI). -UVjVIS Spectroscopy of Vinylogous and Azavinylogous Redox Systems with 1,3,3-Trimethylindolenine as End Group and a Colour Rule for ViolenesThe UV/VIS spectra of the redox system Im, (m = 1 -5 ) are similar for IRed and lox and display polyene type character. The spectra of lsem differ sharply. The two main maxima are shifted bathochromically 110-150 nm per vinylene group. Since A, , ,-m is valid for other radical cations of the violene type, they therefore show the behaviour of cyanines, although HMO calculations indicate configuration interaction for the highest electronic transitions. The spectra of the aza derivatives of 1 are discussed and a method for the determination of serniquinone formation constants from spectral data is given. A. EinfiihrungOffenkettige vinyloge 7c-Systeme lassen sich bekanntlich im Hinblick auf ihre Iangstwellige Absorptionsbande durch zwei Grenzfalle beschreiben: den Polyentyp und den Cyanintyp. Wie empirisch gefunden wurde, ruckt die Absorption beim Polyentyp mit der Wurzel3) aus, beim Cyanintyp 1inea1-4) mit der Anzahl n der Vinylengruppen, nach Iangeren Wellen. Durch Verwendung einer gemeinsamen empirischen Formel die sich *) Korrespondenz bitte an diesen Autor richten.

Electrochemical Properties of Polyimides and Related Imide Compounds

“…For the polyimide and imide systems in this study, the intermediate reduced form, RA-', exhibits a bathochromic shift with characteristic long-wavelength doublet absorbance. A similar behavior has been observed for a violene system for which the strong absorbances were related to the two highest energy transitions involving the single occupied molecular orbital (SOMO) and the LUMO for RA ~- (15). The longest wavelength absorbance (~max) is attributed to the transition HOMO --~ SOMO with the shorter band due to SOMO --* LUMO The plot of 1E~ vs. kma• for RA = in Fig.…”

Molecular design of near infrared polymethine dyes: A review

“…Linhartt [99] have shown that the vinylene shifts decrease regularly upon going to the higher vinylogue. As an illustration, Table 3 presents the observed vinylene shifts for the vinylogous series of the neutral polyenes 9 and their dications 10 containing the same terminal groups as the related polymethine dyes 7.…”

Two step reversible redox systems of the weitz type

“…KSEM's smaller than ~20 have to be determined by UV/VIS spectrometry which can only be applied if all three partners of a given redox system are kinetically reasonably stable. This is the case for 3137) and 3243, 44) 5.2 A Colour Rule for Vinylogous Radical Cations ("Violenes ''2)) From Wurster's salts 4s) and the Weitz system l f i t is well known that the intermediate oxidation level of the radical cations ("violenes") is characterized by an especially long wavelength absorption. This general behaviour may be demonstrated with 32, n = 144) In Fig.…”