It is an object of the present invention to provide a
fluorescence imaging probe capable of selectively visualizing target cells such as cells expressing β-galactosidase (lacZ expressing cells) at a single-
cell level in a
red fluorescence region, and of performing co-
staining together with GFP.An intracellularly-retainable red fluorescent probe comprising a compound represented by the following formula (I) or a salt thereof:wherein: A represents a monovalent group cleaved by an
enzyme; R1 representsa
hydrogen atom, or one to four of the same or different substituents bonded to a
benzene ring; R3, R4, R5, and R6 each independently represent —CFR10R11, —CF2R12, a
hydrogen atom, a hydroxyl group, an
alkyl group, or a
halogen atom, wherein at least one of R3, R4, R5, and R6 is —CFR10R11 or —CF2R12;R2 and R7 each independently represent a
hydrogen atom, a hydroxyl group, an
alkyl group, or a
halogen atom; R8 and R9 each independently represent a
hydrogen atom or an
alkyl group; R10, R11, and R12 each independently represent a
hydrogen atom, an alkyl group, or an alkenyl group; X represents Si(Ra) (Rb), wherein Ra and Rb each independently represent a
hydrogen atom or an alkyl group; and Y is —C(═O)— or —RcC(═O)—, wherein Rc is an alkylene group having 1-3 carbon atoms.