Patent ID: 7943797

Claim:
A compound of formula (I): wherein X 1 is a C 6 or a C 10 aromatic system having a hydroxy group in the alpha position, being optionally substituted by up to four substituents independently selected from the group consisting of: phospho, sulfo, halo, carboxy, acetoxy, C 1 -C 4 alkoxy, linear and branched C 1 -C 4 alkyl; X 2 is a C 6 or a C 10 aromatic system having a hydroxy group in the alpha position, or a five or six membered heterocycle having in the alpha position a heteroatom selected from the group consisting of N, O and S, optionally comprising other N, O or S atoms in their structure, and having from 0-3 double bonds, said aromatic, or heterocyclic system being optionally substituted by up to four substituents independently selected from the group consisting of: phospho, sulfo, halo, carboxy, acetoxy, C 1 -C 4 alkoxy, linear and branched C 1 -C 4 alkyl; Y is (CH 2 ) n or is a xylylene group of formula: n is an integer selected from 2, 3 and 4, R 1 , R 2 are independently selected from the group consisting of H, linear or branched C 1 -C 4 alkyl, C 6 and C 10 aryl.