A compound represented by general formula (IA) or a salt thereof useful as a fluorescent probe for zinc: wherein R1 and R2 represent a hydrogen atom or a group represented by formula (A), wherein X1, X2, X3, and X4 represent a hydrogen atom, an alkyl group, a 2-pyridylmethyl group, or a protective group for an amino group, and m and n represent 0 or 1, provided that R1 and R2 do not simultaneously represent hydrogen atoms; R3 and R4 represent a hydrogen atom or a halogen atom; and R5 and R6 represent a hydrogen atom, an alkylcarbonyl group, or an alkylcarbonyloxymethyl group, and R7 represents a hydrogen atom or an alkyl group