Hemicyanines

The hemicyanine dyes can be represented by structure (5). They may be considered as cyanines in which a benzene ring has been inserted into the conjugated chain. Hemicyanines provide some bright fluorescent red dyes for polyacrylonitrile. 

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The hemicyanines constitute a particular class among streptocyanines in which one of the two nitrogen atoms belongs to a heterocycloammonium. Thiazolohemicyanine corresponds to the general formula in Scheme 31. When R = R, = H. the dyes are of aminovinyl type when R = H. R3 = Ph. they are aniiinovinyl compounds, and when (-CH=CH) is replaced by a benzene ring, they are aminophenyl. 

Dyes, polymethine used for dyes having at least one electron donor and one electron acceptor group linked by methine groups or aza analogues aUopolar cyanine, dye bases, complex cyanine, hemicyanine, merocyanine, oxonol, streptocyanine, and styryl. Supersensitization has been reported for these types—18 cites for cyanines, 3 for merocyanine, and 6 for all other polymethine types. 

The formation of CdS particles beneath monolayers of A-methyl-p-(p-tetradecyl-oxystyryl)pyridinium iodide, a cationic surfactant with a hemicyanine portion was studied [144]. The monolayers were spread on a circular glass trough coated with paraffin, and the trough was covered by ajar. The CdCL subphase also contained EDTA, so the Cd was... 

The strategies used in the synthesis of polymethine dyes are illustrated for a series of indoline derivatives in Scheme 6.1. There is an even wider range of synthetic routes to polymethine dyes than is described here, but they are based for the most part on a similar set of principles. The starting material for the synthesis of this group of polymethine dyes is invariably 2-methylene-1,3,3-trimethylindolenine (121), known universally as Fischer s base. As illustrated in the scheme, compound 121 may be converted by formylation using phosphoryl chloride and dimethylformamide into compound 122, referred to as Fischer s aldehyde, which is also a useful starting material for this series of polymethine dyes. When compound 121 (2 mol) is heated with triethylorthoformate (1 mol) in the presence of a base such as pyridine, the symmetrical cyanine dye, C. I. Basic Red 12 109 is formed. The synthesis of some hemicyanines may be achieved by... 

Benzimidazolium is one of the typical scaffolds of the hemicyanine group, and cationic hemicyanine derivatives can be assumed as potential fluorescent sensors due to their electrostatic interactions. Based on this assumption, Chang and... 

Cao X, Tolbert RW, McHale JL, Edwards WD (1998) Theoretical study of solvent effects on the intramolecular charge transfer of a hemicyanine dye. J Phys Chem A 102(17) 2739-2748... 

Pillai ZS, Sudeep PK, George Thomas K (2003) Effect of viscosity on the singlet-excited state dynamics of some hemicyanine dyes. Res Chem Intermed 29(3) 293-305... 

Ephardt H, Fromherz P (1993) Fluorescence of amphiphilic hemicyanine dyes without free double-bonds. J Phys Chem 97(17) 4540-4547... 

Hubener G, Lambacher A, Fromherz P (2003) Anellated hemicyanine dyes with large symmetrical solvatochromism of absorption and fluorescence. J Phys Chem B 107(31) 7896-7902... 

Fast-response probes (response times less than milliseconds) styrylpyridinium and annellated hemicyanine dyes, merocyanine dyes, and 3-hydroxychromone dyes... 

Fig. 2 Examples of the structures of a few fast-response electric filed sensitive dyes N-(4-sulpho-butyl)-4-(4-(4-(dipentylamino)phenyl)butadienyl)pyridinium inner salt (RH421, a styrylpyridinium dye), ANNINE 5 (an annellated hemicyanine dye), merocyanine 540, and N-[(4 -dimethylamino)-3-hydroxy-6-flavonyl mcthyl-N,N-trimcthyl ammonium (F4N1, a 3-hydroxychromone dye)...

Slow dyes that respond via a redistribution across the entire membrane (sometimes called Nemstain dyes) do so because of a change in the transmembrane electrical potential. As such, they can only be used as probes of the transmembrane potential and not as probes of the surface potential or the dipole potential. Dyes whose electric field sensing mechanism involves a movement between the aqueous medium and its adjacent membrane interface on one side of the membrane can, in principle, respond to changes in both the transmembrane electrical potential and the surface potential. Fast dyes that remain totally in the membrane phase (e.g., styrylpyridinium, annellated hemicyanine, and 3-hydroxyflavone dyes) respond to their local electric field strength, whatever its origin. Therefore, these dyes can, in principle, be used as probes of the transmembrane electrical potential, the surface potential, or the dipole potential. 

Hemicyanine dyes, 9 257 Hemihedrite, 6 471t Hemiisotactic micro structures, 16 108 4,6-Hemiketals, 24 595 Hemimicelle formation, 24 142 Hemins, 14 552... 

Hemicyanine (styryl) dyes are readily obtained by heating Fischer s base with an appropriate aldehyde. Typical products include Cl Basic Red 14 (6.224) and Cl Basic Violet 16 (6.225). The latter dye has been classified by ETAD as toxic [73]. 

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