Metal-cyanine dye having axial ligands which reduce visible absorption

1. An IR-absorbing metal-cyanine dye, said metal having at least one axial ligand bound thereto, wherein said axial ligand comprises a moiety suitable for reducing intermolecular interactions between adjacent dye molecules, thereby minimixing absorption of visible light,

wherein said dye is a metal-cyanine complex of formula (I):

wherein

Q 1 , Q 2 , Q 3 and Q 4 are the same or different and are independently selected from a C 3-20 arylene group or a C 3-20 heteroarylene group;

M is selected from Ga(A 3 ), Al(A 1 ), Mn(A 1 ), Fe(A 1 ) or Pb(A 1 )(A 2 );

A 1 and/or A 2 is of formula (III);

wherein

C 1 represents a core unit having two or more branching poisons;

each P 1 is independently selected from H or a hydrophilic moiety;

g 1 is an integer from 2 to 8;

q 1 is 0 or an integer from 1 to 6; and

each p 1 is independently selected from 0 or an integer from 1 to 6.

2. The dye of claim 1 , wherein said axial ligand reduces intermolecular interactions by steric repulsion.

3. The dye of claim 1 , wherein said axial ligand comprises a polymeric chain.

4. The dye of claim 1 , wherein said axial ligand comprises a dendrimer.

5. The dye of claim 1 , wherein said axial ligand includes a PEG chain.

6. The dye of claim 1 , wherein Q 1 , Q 2 , Q 3 and Q 4 are the same.

7. The dye of claim 1 , wherein C 1 is a atom, an N atom, a Si atom, a C 1-8 alkyl residue, a C 3-8 cycloalkyl residue, or a phenyl residue.

8. The dye of claim 1 , wherein P 1 is a hydrophilic moiety comprising an acid group (including salts thereof), a sulfonamide group, a hydrophilic polymer chain or an ammonium group.

9. The dye of claim 1 , wherein P 1 is of formula: (CH 2 CH 2 O) v R 6 , wherein v is an integer from 2 to 5000 and R 6 is H, C 3-6 alkyl or C(O)C 1-8 alkyl.

10. The dye of claim 1 , wherein P 1 is of formula: SO 3 Z, PO 3 Z 2 , C 1-12 alkyl-CO 2 Z, C 1-12 alkyl-SO 3 Z, C 1-12 -alkyl-PO 3 Z 2 , C 1-12 alkyl-OSO 3 Z or C 1-12 -alkyl-OPO 3 Z 2 , wherein Z is H or a water-soluble cation.

11. The dye of claim 1 , wherein P 1 is of formula: C 1-12 -alkyl-N + (R a )(R b )(R c ) or C 1-12 alkyl-U, wherein R a , R b , R c may be the same or different and are independently selected front H, C 3-8 alkyl, C 6-12 arylalkyl or C 6-12 aryl, and U is pyridinium, imidazolinium or pyrroliniumn.

12. The dye of claim 1 , wherein g is 2, 3 or 4.

13. The dye of claim 1 , wherein A 1 and/or A 2 is a pentaerythritol derivative (A), a triethanolamine derivative (B), a phloroglucinol derivative (C), or a 3,5-dihydroxybenzyl alcohol derivative (D):

wherein is P 1 is as defined in claim 1 .

14. The dye of claim 1 , wherein Q 1 ,Q 2 ,Q 3 and Q 4 are selected from an arylene or heteroaylene group of the formula:

wherein

R 1 and R 2 may be the same or different and are selected from hydrogen, hydroxyl, C 1-12 alkyl, C 1-12 alkyl bearing a hydrophilic or hydrophilizable group, C 1-12 alkoxy, C 1-12 alkoxy bearing a hydrophilic or hydrophilizable, group, amino, C 1-12 alkylamino, di(C 1-12 alkyl)amino, halogen, cyano, thiol, C 1-12 alkylthio, nitro, carboxy, C 1-12 alkylcarbonyl, C 1-12 alkoxycarbonyl, C 1-12 alkylcarbonyloxy or C 1-12 alkylcarbonylamino;

T is selected from a substituent comprising a polymeric chain or a C 3-30 hydrocarbyl group;

W is hydrophilic group;

E is selected from —OH, —O, C 3-6 alkyl, carboxy-C 1-6 alkyl, sulfo-C 1-6 alkyl, C 1-6 alkoxy, C 5-12 arylalkyl, C 1-6 alkylcarbonyl, C 5-12 arylalkylcarbonyl, C 1-6 alkoxycarbonyl or C 5-12 arylalkoxycarbonyl;

m is 0, 1 or 2;

n is 0, 1 or 2; and

p is 0, 1 or 2.

15. The dye of claim 14 , wherein R 1 and R 2 are selected from hydrogen or C 1-8 alkoxy.

16. The dye of claim 14 , wherein W is selected from a substituent comprising a PEG chain; a substituent comprising an ammonium group; a substituent comprising an acid group, including salts thereof; a substituent comprising a sulfonamide group.

17. An ink comprising a dye according to claim 1 .

18. An inkjet ink comprising a dye according to claim 1 and a singlet oxygen quencher.

19. An inkjet ink comprising a dye according to claim 1 , said dye being preselected to minimize visible absorption by reducing intermolecular interactions between adjacent dye molecules.