Heterocyclic fluorescent dyes and method of production thereof

A compound of formula

• wherein Ar′ is a homo- or heteroaromatic system, which is selected from
• wherein the dotted lines are bonds to the 6-membered ring, the dotted line is a bond to a carbon atom in para-position to the nitrogen atom, the dotted line is a bond to a carbon atom in meta-position to the nitrogen atom, wherein R1, R1′ and R1″ are each independently H, halogen, cyano, C1-C25alkoxy, C1-C25alkyl substituted with a halogen atom, or C1-C25alkyl,
• R2 is H, halogen, cyano, C1-C25alkoxy, or C1-C25alkyl, R3′ is Cl, Br, or I,
• wherein R22 to R25 are each independently H, halogen, cyano, C1-C25alkoxy, C1-C25allyl substituted with a halogen atom, or C1-C25alkyl, and
• R26′ is Cl, Br, or I;
• X is O, S, Se, or NR4,
• R4 is hydrogen, C6-C18aryl;
• C6-C18aryl which is substituted by C1-C18alkyl, or C1-C18alkoxy;
• C1-C25alkyl, which may optionally be interrupted by an oxygen or sulphur atom and/or is optionally substituted by a halogen atom;
• or C7-C25arylalkyl.