Effective Tuning of Ketocyanine Derivatives through Acceptor Substitution

Abstract

A series of ketocyanine derivatives possessing bis(diarylamino)fluorenyl donors and variable acceptors installed at the bridging carbon atom were synthesized to investigate how the electronic structure of the dye can be systemically tuned through stabilization of the cyanine-like character of the donor by increasing the acceptor strength. Analysis of the (1) H NMR spectra indicates that the "charge-separated" species dominates in these dyes, given that carbons possessing a positive or negative charge in the resonance structures of this state purposefully shift downfield or upfield, respectively, depending on the strength of the acceptor moiety. In DAA-Fl-PI, the acceptor strength and the gain of acceptor aromaticity indicates a predisposition of the separated state, indicated by asymmetry in the (1) H NMR spectrum, as well as uneven distribution of the HOMO on the fluorenyl donor.

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

“…Consequently many quantitative calculations concerning dyes which incorporated the effect of Duschinsky rotation were performed, whose modus operandi are consistent with the conclusion that “…the shoulders are not determined by a unique, dominant, vibrational normal mode but rather by a collection of singly excited vibrations.”…”

“…Consequently many quantitative calculations concerning dyes which incorporated the effecto fD uschinsky rotation were performed, [37][38][39][40][41][42][43][44] whose modus operandi are consistent with the conclusion that "…the shoulders are not determined by au nique, dominant, vibrational normal mode but rather by ac ollection of singly excited vibrations." [35] In the following section we will discuss the "rightness"o f both models in light of spectroscopic data obtained from instrumental measurement.…”

“…Because variations in vibrational frequency pertaining to this part of the chromophorei nduced by differences in groups at each end of the cyanine dyes tructure are relativelys mall, it mayb ed educed that the sub-bands arise from the coupling of av ibration of the polymethine chain with the S 0 -S 1 electronic transition.It is noteworthy that in Refs. [35,[37][38][39][40][41][42][43][44],P ouradier's work wasn either cited, nor was his analysis of experimental spectrad iscussed.…”

Fluorenone imidazolium salts as novel de Vries materials

“…122 The intense bands at 272-274 nm were assigned to the p-p* transition of the uorenone core. 123,124 The UV/vis spectra were neither affected by different donor groups at the uorenone core, i.e. methoxy, alkoxy or hydroxy nor different anions (bromide vs. triate).…”

“…16, inset). 123,124 For potential applications bulk emission properties are particularly interesting. Therefore, selected samples were studied by solid state uorescence spectroscopy utilizing a polarizing optical microscope equipped with UV light source (l exc ¼ 350-380 nm) and photodetector.…”