Methine cyanine

Applying this rule, the preceding dyes are written (3-methyl-4-phenyl-thiazole-2)(3-methylthiazole-2)methine cyanine iodide (3a) and (3-methyl-4-phenylthiazole-2)( l-methylquinoline-2)methine cyanine iodide (4), respectively. Any substituent in the chain is named and its position designated by a, ft or y, for example, (3-methyl-4-phenylthia2ole-2)(3-methylthiazole-2)-/S-methyltrimethine cyanine iodide (3b). 

Rhodacyanines possess two chromophoric systems. They are at the same time neutrocyanine derivatives, which involves position 5 of the ketomethylene, and methine cyanine, which involves position 2. Following lUPAC s standard nomenclature rules, structure 7 is named 3-ethyl-4-phenyl-2- 4-oxo-3-ethyl-5-[2-(3-ethy]-2,3-dihydro-benzo-l,3-thiazo-lylidene)ethylidene]-tetrahydro-l,3-thiazolylidene-methyl -1.3-thiazolium iodide (Scheme 5). It implies that the 4-phenyl thiazole ring having the... 

These dyes possess two independent chromophoric chains of even methine (neutro) and uneven methine (cyanine) fixed on a central ketometbylene nucleus. The methylene reactive group is first used for the neutrocyanine synthesis in position 5. the, quaternization of which can ensure a subsequent polymethine synthesis in position 2 of a cationic dye by ordinary means (Scheme 58). As indicated, this quaternized neutrocyanine (37) may as well give another neutrocyanine. 

Reaction of the quaternized salts of 4-ethoxycarbonyl-3,5-dimethyl-f-phenylpyttolo(furo or thieno)[2,3-c]pyrazole 34 with the iodomethane quaternary salts of pyridine, quinoline, and isoquinoline in ethanol with catalytic piperidine gave 3-[4(f)]-monomethine cyanine dyes (e.g., 35). Additionally, 3-[2(4)]-trimethine cyanine dyes and 4-[2(4)]-di-3[2(4)]-tri-mixed methine cyanine dyes (e.g., 36 and 37, respectively) were similarly prepared from the intermediates derived by reaction of 34 with triethyl orthoformate in the presence of piperidine (Scheme 8) <2002CCS106f>. 

Unsymmetrically substituted phospha-methin-cyanines 9 with two different heterocyclic bases can also be synthesized. Here the quaternary salt of one heterocyclic base (e. g. 4) is reacted with tris-hydroxymethyl-phosphine 5 in dimethyl-formamide or glacial acetic acid without the addition of a base. Then one mole of the quaternary salt of the other heterocyclic base (e. g. 10) and the base are added. The base deprotonates the hydroxymethyl groups of the phosphine 5, thus liberating formaldehyde and yielding the phosphine base which then reacts with the second quaternary salt ... 

Fig. 1. UV ectraof bis-[N-ethyl-benzthiazole(2) -phospha-methin-cyanine-tetrafluoro-boratc compared with the aza- and the carbomethine-cyanine...

By investigating labeled methin-cyanine analogs v/e have found that the chemical shift of the signals show a quite similar dependence on the nature of the basic ring... 

Fig. 4. X-ray structure of bis-lN-ethyl-benzthiazoIe-(2)l-phospha-methin-cyanine-perchlorate...

Phosphamethin-cyanines, like methin-cyanines, can be protonated by strong acids, forming colorless dications. These can be converted back to the original phosphamethin-cyanines by careful addition of weak bases such as tert.-butanol. This acid-base reaction is least successful in the case of the weakly basic bis-benzthiazole-phosphamethin-cyanine 6. For bis-quinoline-phosphamethin-cyanine 7 b, we obtained vnth perchloric acid in glacial acetic acid the absorption spectrum of the N-ethyl-quinolinium salt. 

Cyanines s. Mero-, Poly-methine-cyanines Cyano. . . s. a. Di-cyano. . Tetra-, Tri-... 

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