Patent ID: 7220843

Claim:
A compound of the general formula (I) wherein M is two hydrogen atoms or one metal ion selected from the group consisting of Cu, Co, Ni, Mn, Zn and Al; A is R 1 is H, OH or —NH—(CH 2 ) a —SO 3 − X + where a is from 1 to 6; R 2 is H or a radical of the formulae D is C 6 H 4 , C 6 H 3 (OH) or C 6 H 3 (OCH 3 ); X is H, alkali metal, NH 4 , C 1 –C 18 -alkyl-NH 3 , (C 1 –C 18 -alkyl) 2 NH 2 , (C 1 –C 18 -alkyl) 3 NH, (C 1 –C 18 -alkyl) 3 CNH 3 , (C 1 –C 18 -alkyl) 2 CHNH 3 , or (C 1 –C 18 -alkyl) 4 N, and n is from 1 to 4.