Bond length alternation in unsymmetrical cyanine dyes and its influence on the vibrational structure of their electronic absorption spectra

Abstract

Based on the assumption that the unsymmetrical cyanine dyes can be regarded as a hybrid of the two corresponding symmetrical dyes it was expected that λmax of the unsymmetrical dye would be the arithmetic mean of λmax of the two symmetrical dyes. There is, however, often a remarkable difference between the arithmetic mean and the observed λmax of the unsymmetrical dye – the Brooker deviation. To date, this effect is explained in terms of increasing electronic energy differences. With increasing difference of the electronic structure between the ground and excited state, the difference between equilibrium geometry of ground and excited state increases and the relative intensity of the higher vibronic transitions 0–v increases and that of the 0–0 transition decreases. λmax represents the intensity maximum of an absorption band and could be related to the 0–0, 0–1 or another vibronic transition. We discuss the origin of the Brooker deviation on the vibrational structure of the spectra.

Fine Structure in Electronic Spectra of Cyanine Dyes: Are Sub‐Bands Largely Determined by a Dominant Vibration or a Collection of Singly Excited Vibrations?

“…To the best of our knowledge, in 1960, Werner Maier and Friedrich Dörr were the first to discuss the sub‐bands present in cyanine dye spectra in the context of the Franck–Condon principle (FCP) and the coupling of a dominant Raman‐active vibration with the electronic transition . During the next half century or so, the intensity distribution among the sub‐bands in cyanine dye spectra was explained by the FCP assuming the sub‐bands in cyanine dye spectra are largely determined by coupling of a dominant, totally symmetric vibration with the electronic transition …”

“…[24] During the next half centuryo rs o, the intensity distribution among the sub-bands in cyanine dye spectra was explained by the FCP assuming the sub-bands in cyanine dye spectra are largely determined by coupling of ad ominant, totally symmetric vibrationwith the electronic transition. [25][26][27][28][29][30][31][32][33][34] In 2007, Guillaumee tal. reported the first application of density and time-dependent density functional theory (DFT, TDDFT) in an attemptt os imulate the absorption and emission spectra of ac yanine dye.…”

Novel Trimethine Cyanine Dye as Potential Amyloid Marker

“…Numerical studies indicate that the absorption spectra of cyanine dyes possess a vibronic structure with the relative intensities of 0-0 and 0-1 sub-bands being dependent on the dye structure [43,44]. The main absorption band of AK3-1 centered at ~ 622 nm in the buffer solution (637 nm in DMSO) corresponds to the 0-0 transition, whereas a second subband can be assigned to 0-1 transition.…”

Rationale Auswahl von Cyaninen zur Erzeugung von konjugierter Säure und freien Radikalen für die Photopolymerisation durch Belichtung bei 860 nm

“…Entweder variiert die Indoliumeinheit, oder die Länge der Polymethinkette ist unterschiedlich. Jede Erweiterung des Polymethins um zwei Methingruppen führt typischerweise zu einer bathochromen Absorptionsverschiebung von 100 nm [1–5, 7, 52–55] . Darüber hinaus zeigt der Vergleich eines Cyanins mit einer Indolium‐Einheit mit dem einer Benzo[ cd ]indolium‐Endgruppe eine bathochrome Verschiebung der Absorption um 200 nm [5] …”