Methine dyes

The invention comprises asymmetrical cyanine dye salts of formula where A is methylene, substituted methylene or where Y represents the atoms to complete a benzene or substituted benzene ring, n is 2 or 3, R1 and R2 are alkyl, substituted alkyl, allyl, aryl, substituted aryl, benzyl, substituted benzyl or cycloalkyl, X is an acid radical, r and m are 1 and 2 and Z represents the number of atoms to complete a heterocyclic nucleus containing 5 or 6 atoms. The invention also comprises merocyanine dyes of formula wherein A, n and R1 are the same as above and P and Q are cyano or together complete a heterocyclic ketomethylene nucleus. The cyanine dye salts may be prepared by condensing a 1 : 5-cyclomethylene tetrazolium quaternary salt of formula where R1, n, A and X are as above with a cycloammonium quaternary salt of formula wherein R2, X, Z and m are as above and D is alkyl- or aryl-mercapto, b -alkyl- or b -aryl-mercaptovinyl, b -arylaminovinyl, b -acetanilidovinyl or b -p-tolusulphamilido group, or with a heterocyclic base of formula where R2, Z and m are as above and Y is an aryl-N = group. The merocyanine dyes may be prepared by condensing the 1 : 5-cyclomethylene tetrasodium quaternary salt of the above formula with a heterocyclic compound of formula where P and Q are as above and E is alkoxy, arylimino or an acetarylido group. 3 - Ethyl - 4,5 - dihydrotetrazole - quinolinium iodide is reacted with 2-(b -anilethylidene) -3-ethyl - 5 - phenyl - 2,3 - dihydrobenzoxazole; 1,3 - diethyl - 2[b - (p - tolusulphoanilido)vinyl]-5 - cyano benzimidazolium chloride; 2 - [b -(acetanilido)vinyl] - 3 - ethyl - 5 - phenyl benzothiazolium iodide; 2-methylmercapto-3-methylbenzothiazolium methyl sulphate; 2-(b -anilethylidene) - 3 - ethyl - 2,3 - dihydrobenzselenazole or 2-[b -(acetanilido)vinyl]-3-ethyl naphtho - [1 : 2 - d] - thiazolium iodide to produce the appropriate cyanine dye. Cyanine dyes are also prepared by reacting 1-ethyl or 1-methyl-6,7 - dihydro - 5H - pyrrolotetrazolium ethyl or alkyl sulphate with 2-(b -anilethylidene) -3-ethylthiazolidine; 2 - b - (acetanilido) - vinyl - 3-ethyl-benzoxazilium iodide or 2-(b -anilethylidene) - 3 - ethyl - 2,3 - dihydrobenzthiazole. Other cyanine dyes are prepared by reacting 1 - ethyl - 5,6,7,8 - tetrahydrotetrazolopyridinium ethyl sulphate with 2-(b -(anil)-ethy