GB562568A - Improvements in or relating to polymethine dyes - Google Patents

Abstract

Dicarbocyanine dyes are produced by condensing a compound of the general formula R1S-CH=CH-CH(XR1)2, wherein the groups R1 are alkyl groups and the groups X are both O atoms or both S atoms with an alkyl or aralkyl quaternary salt of a 5- or 6-membered heterocyclic nitrogen compound containing a reactive methylene group substituted in the a -position to the quaternary nitrogen atom. The reactive methylene group may be a methyl or mono-substituted methyl group. The dyes may have the formula <FORM:0562568/IV/1> wherein R2 and R3 represent alkyl or aralkyl groups or R2 may be H and R3 an unsaturated aliphatic group (e.g. allyl) or a substituted alkyl group (e.g. hydroxyalkyl), D represents the residue of a heterocyclic nitrogen nucleus, and A represents an acid radical. The quaternary salt may be derived from the following nitrogen compounds: substituted and unsubstituted thiazoles, thiazolines, oxazoles, oxazolines, selenazoles, selenazolines, pyridine, quinoline, indolenine, diazines (e.g. pyrimidine and the diazines described in Specification 425,609), thiodiazoles, and quinazoline, and the corresponding substituted and unsubstituted polycyclic compounds such as benzthiazoles, naphthathiazoles, and anthrathiazoles, and the corresponding polycyclic oxazoles and selenazoles. The polycyclic compounds may contain substituent groups in the benzene nuclei, e.g. alkyl, aryl, amino hydroxy and alkoxy groups, and halogen atoms. The quaternary salts may be chlorides, bromides, iodides, alkyl sulphates, p-toluenesulphonates, or perchlorates. Where X is oxygen, the reagents may be heated together in the presence of a base and a solvent, pyridine serving both purposes. Where X is sulphur, the reagents are heated together in the presence of a solvent and a substance which will combine with the split-off alkyl mercaptan (e.g. acetic anhydride serving both purposes), and the reaction is finished by adding a base and heating for a further period. 2 : 21-Diethylthiadicarbocyanine iodide is prepared by refluxing together 1-methylbenzthiazole ethiodide, b -ethylthioacrolein diethyl acetal and pyridine, and pouring the reaction mixture into aqueous potassium iodide. 1 : 11-Diethyl-2 : 21-quinodicarbocyanine iodide is prepared by refluxing together quinaldine ethiodide, b -ethylthioacrolein diethyl mercaptal and acetic anhydride, adding triethylamine, and continuing heating. 1 : 11-Dimethylindodicarbocyanine iodide and 3 : 31-dimethylthiazolinodicarbocyanine iodide are similarly prepared. Photographic sensitizing data are given in respect of the last dye. Specification 562,565 also is referred to.