Metal-cyanine dye having improved water solubility

1. An IR-absorbing dye which 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 Ti(A 1 )(A 2 ), Zr(A 1 )(A 2 ), V(A 1 )(A 2 ), Si(A 1 )(A 2 ), Ge(A 1 )(A 2 ), Ga(A 1 ), Al(A 1 ), Mn(A 1 ), Fe(A 1 ), Sn(A 1 )(A 2 ), or Pb(A 1 )(A 2 ); and

A 1 and A 2 may be the same or different and are axial ligands of formula (IIIa)

wherein:

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

each P 1 is independently selected from H, a hydrophilic moiety or a branched 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 Q 1 , Q 2 , Q 3 and Q 4 are the same.

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

4. 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 1-6 alkyl or C(O)C 1-8 alkyl.

5. The dye of claim 1 , wherein P 1 is of formula: SO 3 Z, P 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.

6. 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 from H, C 1-8 alkyl, C 6-12 arylalkyl or C 6-12 aryl, and U is pyridinium, imidazolinium or pyrrolinium.

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

8. 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 8 .

9. The dye of claim 1 , wherein Q 1 , Q 2 , Q 3 and Q 4 are selected from an arylene or heteroarylene 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 alkoxy, 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 1-2 alkylcarbonylamino;

T is selected C 1-30 hydrocarbyl group;

W is a hydrophilic group;

E is selected from —OH, —O − , C 1-6 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 arylalkylcarhonyl, 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.

10. The dye of claim 9 , wherein R 1 and R 2 are selected from hydrogen or C 1-8 alkoxy.

11. The dye of claim 9 , wherein W is selected from a substituent comprising a PEG chain; a substituent comprising an ammonium group; a substituent comprising a sulfonic acid group, including salts thereof; a substituent comprising a sulfonamide group.