Rigidized trimethine cyanine dyes

A compound (I) of formula:

• substituted by groups R2–R9, wherein groups R6, R7, R8 and R9 are attached to the atoms of the Za and Zb ring structures;
• R2 to R9 are the same or different and are —R10 or -L-R10 where R10 is selected from hydrogen, halogen, amide, C1–C6 alkoxy, nitro, cyano, aryl, heteroaryl, sulphonate, quaternary ammonium, guanidium, hydroxyl, phosphate, phosphonate, optionally substituted amino, azido, sulphydryl, carboxyl, carbonyl and reactive groups selected from succinimidyl ester, isothiocyanate, anhydride, haloacetamide, maleimide, sulphonyl halide, phosphoramidite, acid halide, alkylimidate, hydrazide and carbodiimide, and L is selected from the group consisting of a straight or branched C1-20 alkyl chain, a C2-20 monoether or polyether and a C2-20 atom chain containing up to four secondary amide linkages;
• R1 is selected from hydrogen, aryl, heteroaryl, cyano, nitro, aldehyde, halogen, hydroxy, amino, quaternary amino, acetal, ketal, phosphoryl, sulphydryl, and alkyl groups optionally substituted by amino, C1-4 alkyl-substituted amino, quaternary amino, aldehyde, ketone, acetal, ketal, halo, cyano, aryl, heteroaryl, hydroxyl, sulphonate, sulphate, carboxylate, amide and nitro;
• A is selected from O, S and NR11 where R11 is the substituted amino radical:
• where R′ is selected from hydrogen, a C1-4 alkyl and aryl and R″ is selected from C1-18 alkyl, aryl, heteroaryl, an acyl radical having from 2–7 carbon atoms , and a thiocarbamoyl radical;
• X and Y may be the same or different and are selected from bis-C1–C4 alkyl and C4–C5 spiro alkyl substituted carbon, oxygen, sulphur, selenium, CH═CH, and N—W wherein N is nitrogen and W is selected from hydrogen, a group —(CH2)nR12 where n is an integer from 1 to 26 and R12 is selected from hydrogen, amino, aldehyde, acetal, ketal, halo, cyano, aryl, heteroaryl, hydroxyl, sulphonate, sulphate, carboxylate, substituted amino, quaternary amino, nitro, primary amide and substituted amide;
• Za and Zb each represent the atoms necessary to complete one, or two fused aromatic rings each ring having six carbon atoms;
• provided that when X and Y are other than carbon, at least one of R2–R9 represents -L-R10 or R10 wherein R10 is said reactive group or,
• when X and Y are different and are selected from O and Se, at least one of R1–R9 is other than hydrogen, methyl, phenyl or naphthyl.