Synthesen mit aliphatischen Dialdehyden, XXV. δ‐Substituierte Heptamethincyanin‐Farbstoffe mit Indolenin‐Endgruppen

Abstract

Durch Kondensation der Glutaconaldehyd‐Derivate 3–8 mit dem heterocyclischen Iminiumsalz 2 werden Heptamethincyanin‐Farbstoffe 1a–g erhalten, die in δ (oder meso)‐Stellung der Heptamethinkette elektronenanziehende und elektronenabgebende Substituenten tragen. Der Einfluß dieser Substituenten auf die Lage der längstwelligen UV/VIS‐Absorptionsbanden (Tab. 1) sowie auf die 1H‐ und 13C‐NMR‐chemischen Verschiebungen der Heptamethinwasserstoff‐ und ‐kohlenstoffatome von 1a–g (Tab. 2 und 3; Abb. 1) wird untersucht.

Deciphering the Structure–Property Relations in Substituted Heptamethine Cyanines

“…The C3′ substituents exhibited a considerably weaker influence on the absorption maxima than the C4′ substituents. This observation is further reinforced by the comparison of 1d (λ abs = 733 nm) and 1e (λ abs = 736 nm) with 1a and the corresponding C4′-chloro and C4′-bromo regioisomers reported previously, possessing absorption maxima at ∼770 nm . The bathochromically shifted maximum of broadly utilized cyanine 2 (IR-775) compared to that of the parent 1a can be related to a weak electron-accepting ability of the C4′-chloro substituent (σ P = 0.23) .…”

“…The heptamethine cyanine dyes studied herein (Figure ) were synthesized by ring-opening of the corresponding Zincke salts reported recently or, in the case of 1o , according to the procedure reported previously . The propensity of these dyes to aggregate in aqueous media can significantly affect their optical and photophysical properties.…”

“…Reagents and solvents of the highest purity available were used as purchased, or they were purified/dried using standard methods when necessary. The compounds were synthesized according to the published procedures , or purchased from Sigma-Aldrich ( 2 , ICG ( 5 ), IR-783).…”

“…It was prepared according to the reported procedure . 1,2,3,3-Tetramethyl-3 H -benzo­[ g ]­indolium iodide (0.42 g, 1.38 mmol) was dissolved in hot dry pyridine (2 mL) under a N 2 atmosphere.…”

On the Signalling Pathways and CuII‐Mediated Anion Indication of N‐meso‐Substituted Heptamethine Cyanine Dyes

“…Electron-donating or -accepting substituents thus primarily destabilise or stabilise the LUMO, leading to the respective hypso-or bathochromic shifts. Kuhns theory has been verified in several experimental studies, [38,39] suggesting that also for dyes such as those studied here and in references [19][20][21] the classic www.chemeurj.org theory should be valid and ICT processes in a conventional sense are not involved. [40] Since the nitrogen atoms of the meso substituents participate in the electron distribution in the LUMO, differences in k r can arise as found here for 2 and 3 versus 4 and 5.…”