A compound represented by formula (I):Formula (I) wherein Z1 is atoms necessary for forming an aromatic ring; Z2 is atoms necessary for forming an aromatic hetero ring; V1 and V2 each are a substituent, and at least one of V1 and V2 is a hydroxyl, primary- or secondary- or tertiary-amino, acylamino, or sulfonamido group; r is 1 to 4; s is 1 to 4; the ring formed by Z1 or Z2 may have a substituent other than V1 or V2; M1 is a counter ion; m1 is the number necessary for neutralizing charge; and X1 and X2 each are a carbon or hetero atom, and at least one of X1 and X2 is a hetero atom.