Pentamethines

Low yield in pentamethine thiazolocyanine results also from the fission of the pyridine ring in the presence of 2-chloro-3.3-dimethylindolenine (544). Explanations of this unusual reaction have been given (Scheme 44) (67). 

In WORM disks, pentamethine and heptamethine are the materials of choice (see Cyanine dyes Polymethine dyes). 

Optical properties of cyanines can be usefiil for both chiral substituents/environments and also third-order nonlinear optical properties in polymer films. Methine-chain substituted die arbo cyanines have been prepared from a chiral dialdehyde (S)-(+)-2-j -butylmalonaldehyde [127473-57-8] (79), where the chiral properties are introduced via the chiral j -butyl group on the central methine carbon of the pentamethine (die arbo cyanine) chromophore. For a nonchiral oxadicarbocyanine, the dimeric aggregate form of the dye shows circular dichroism when trapped in y-cyclodextrin (80). Attempts to prepare polymers with carbocyanine repeat units (linked by flexible chains) gave oligomers with only two or three repeat units (81). However, these materials... 

Fig. 9. Examples of dyes used in optical disks. (14), pentamethine cyanine [36536-22-8] (1 )> nickel dithiene complex [38465-55-3] and (16) lR-810.

Pentamethinic systems with heterocyclic substituents 97CLY387. 

Chain-bridged cyanines, see Thiazoio-cyanines, chain-bridged Chain-bridged thiazolocyanines, see Thia-zolocyanines, chain-bridged Charge distribution, on methine chain, 72 2-Chloro-3,3-dimethylindolenine, in synthesis of pentamethine thiazolocyanines. 56... 

Pariser-Parr-Pople calculations, 72 calculations of thiazolocyanines, 73 of thiazolium salts, 31 Pentamethine thiazolocyanines, chain-bridged, synthesis of. 58 cleavage of, 63 nomenclature of. 26 synthesis of, 56... 

Detailed studies on this line are in progress in our laboratory in an attempt to reach equally clear conclusions for more complex cyanines characterized by the same (pentamethine) chromophore as BMPC (e.g. DOC and DTC). 

Various hybrid compounds comprised of two types of nitroxide radicals and either a pentamethine (Cy5) or trimethine cyanine (Cy3) were synthesized by Sato and co-workers [32]. These compounds seem to be promising fluorescent chemo-sensors for the measurement of reducing species such as Fe2+, ascorbic acid, and hydroxyl radicals. 

Pentagonal bipyramidal geometry, for metal coordination numbers, 7 574 Pentaheteroglycans, classification by structure, 4 723t Pentalene ligand, 24 772-773 Pentamethine dyes, 9 505 Pentamethylantimony, 3 77 Pentamethylcyclopentadiene, 25 116 Pentamethylcyclopentasiloxane,... 

Scheme 1. Principle of cyanine dye synthesis leading to trimethine (n = l), pentamethine (n = 2) and heptamethine (n = 3) chromophores. Structures comprising indolic subunits are usually named indocarbocyanine, indodicarbocyanine and indotricarbocyanine, respectively. Formic acid, malonic aldehyde, glutaconic aldehyde are used in their protected dianUide or orthoester form. They can be applied as substituted derivatives to introduce residues into the polymethine unit. The indolic substructure might bear further residues or annelated aromatic rings...

Strongly electron-releasing groups at the 2-, 4- and 6-positions of the pyrylium salts (39) exert a profound effect on the chemical shift of H(3) and H(5), which are moved upheld by 2-3 ppm. It is proposed that such compounds are better described as bridged pentamethine cyanines (40) (88MRC707). 

---