A compound represented by formula (I):
Formula (I)
wherein Z
1
is atoms necessary for forming an aromatic ring; Z
2
is atoms necessary for forming an aromatic hetero ring; V
1
and V
2
each are a substituent, and at least one of V
1
and V
2
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 Z
1
or Z
2
may have a substituent other than V
1
or V
2
; M
1
is a counter ion; m
1
is the number necessary for neutralizing charge; and X
1
and X
2
each are a carbon or hetero atom, and at least one of X
1
and X
2
is a hetero atom.