SQUARYLIUMFARBSTOFFE

摘要

Squarylium compounds of formula (I) (in which Q<1> and Q<2> are each a chromophoric group having an aromatic unsaturated system conjugated with the squarylium ring and such that in the compounds of formulae Q<1>CH2R<1> and Q<2>CH2R<2> the methylene hydrogens are active hydrogen; R<1> and R<2> are each independently a hydrogen atom or an aliphatic or cycloaliphatic group; and OMEGA is a group of the formula -NR<3>R<4> or of the formula -CR<5>R<6>R<7>, wherein: R<3> and R<4> are each independently a hydrogen atom, or an acyl, aliphatic, cycloaliphatic, aromatic or heterocyclic group, subject to the proviso that one of R<3> and R<4> may be an amino, substituted amino group, or organosulfonyl group, or R<3> and R<4> together with the intervening nitrogen atom form a nitrogenous heterocyclic ring; and R<5>, R<6> and R<7> are each independently a hydrogen atom, or an acyl, aliphatic, cycloaliphatic, aromatic or heterocyclic group, or an electron-withdrawing group able to lower the electron density at the carbon atom to which it is attached) are useful as near infrared absorbers. The presence of the OMEGA group on the squarylium ring enables minor changes in absorption wavelength to be achieved by modifications of this group, and also allows functional groups to be incorporated into the dye without changing the chromophoric groups.