Cyanine

The name found its origin in the fact that the first dyes known were all derived from quinoline as, for example, 2,2 -cyanine (Scheme 1). In the case of an asymmetrical or symmetrical dye involving one or two nuclei that are different from the quinoline ring, the name of the nucleus becomes the prefix in the name of the dye. So 3.3 -dimethyl-4-phenyl thiazolo cyanine is the dye of structure 1 and 3.1 -dimethyl 4-phenyl thiazolo 2 -cyanine is represented by the formula structure 2 (Scheme 2). 

Tran [391,392] has reported ng detection of dyes on filter paper by SERS. Silver colloidal hydrosols stabilised by filter supports enhance the Raman scattering of adsorbed dyes. Typical detection limits are 500 pg (crystal violet), 7 ng (l,l,9-trimethyl-2,2 -cyanine perchlorate), 15 ng (3,3 -diethylthiacarbocyanine chloride) and 240 ng (methyl red) using a 3 mW He-Ne laser. 

Figure 6.17. Absorption spectra of l,r-diethyI-2,2 -cyanine bromide in ethylene glycol water (1 1) at room temperature and at 173°K, showing the //-aggregate states.(84> Reprinted by permission of Chemical Physics Letters.

Figure 6.18. Absorption and fluorescence spectra of l,r-diethyl-2,2 -cyanine bromide at 298 and 77°K. Fluorescence excitation at 498 nm and 565 nm, as indicated by arrows/941 Reprinted by permission of Chemical Physics Letters.

Table 6.8. Spectral Shifts of Aggregated States of 1,1 -Diethyl-2,2 -cyanine Bromide in Ethylene Glycol-Water Matrix at 173°Ka...

Auf diese Weise errechnete sich im Sattigungsbereich die zur Adsorption eines 1,1 -Dimethyl-2,2 -Cyanin-Ions durchschnittlich verfug-bare Halogensilberflache zu 73,6 A2. 

Abb. 9 veranschaulicht einen Schnitt durch das 1,1 -Dimethyl-2, 2 -Cyanin-Ion in der Ebene des konjugierten Systems. Der Dar-stellung wird entnommen, daB das Ion in der Lange 15,9 A und in der Hohe 8,1 A miBt. Die Dicke einer Farbmolekel ist 3,7 A, wenn die van der WAALSsche Dicke der vorhandenen Heterocyclen zugrunde gelegt wird. 

Das Beispiel eines Verbindungspaars, bei dem eine Antisensibilisierung stattfindet, liefern die Verbindung 1,4 -Diathyl-2,2 -cyanin Pseudoisocyanin)... 

The known factors which influence the solution spectra of cyanines have been recently reviewed (14, 46, 73). It will be sufficient to summarize here some of the concentration-dependent spectral properties for the specific case of l,l -diethyl-2,2 -cyanine this cyanine was employed in many of the present experiments. In alcohol as in dilute water solutions this dye, which will be referred to as Pseudocyanine, although it has also been called Pseudoisocyanine, appears to exist only in an extended configuration and has its maximum absorption near 523 n.m. This transition... 

As noted, the uniformity of the detector used to make absorption measurement and whether it is energy-based or Figure 5.3.5-2 CR Absorption spectmm of aqueous quantum-flux based should be determined. A major solutions of diethyl-2,2 -cyanine chloride at 25C (1) 1.3 x problem has occurred in psychophysically determiningthe 5M 1-3 x 10 3M (3)7.1 x 10 3M (4) 1.4 x 10... 

The detailed geometry of the liquid crystal formed by the Rhodonine family has not been documented to date. However, Figure 5.5.8-2 illustrates the geometries assumed by related chromophores115. (a) shows the configuration assumed by 2,2 cyanine when formed as a liquid crystalline film on water, (b) shows the same liquid crystalline configuration in more detail. Note the distance between the two Nitrogen atoms which form the dipole of the molecule. 

In this respect adsorption of dyes has been popular, especially because their colour allows rapid and accurate spectroscopic detection in the supernatant. However, caveats (i) and (il) above also apply to these adsorbates. For a discussion the reader may consult the proceedings of a symposium devoted to surface area determination in general containing a contribution by Padday in which the outcome of a comparative survey over 19 different laboratories was reported, dealing with the adsorption of the dye 1,1 - diethyl-2,2 cyanine on silver bromide and a few other adsorbents. Giles et al. have given a list of recommended a -values ... 

The preferential orientation of single chromopho-res is obtained when a monolayer of N,N -dioctadecy1-2,2 -cyanine (dye A, Figure 6) in a mixed monolayer with arachidic acid and methylarachidate, molar ratio dye A acid ester = 1 1 9, is slowly transferred... 

This new emission was also detected in other cyanines [16,88], such as 2,2 -cyanine [88b] and oxacyanine dyes [88a]. Energy studies revealed a supralinear dependence on laser energy. 

Cyanines are dyes with a general formula as follows ... 

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