Synthetic procedures and product characterization data, zinc binding analysis methods, selectivity and pH dependence charts. This material is available free of charge via the Internet at http://pubs.acs.edu.A xanthene-forming condensation reaction yields rhodol and rhodamine dyes carrying a zinc-binding ligand that includes the aniline-type nitrogen donor of the fluorophores. Upon zinc coordination in neutral aqueous solution, rhodol RF3 behaves as a ratiometric sensor, and rhodamine RA1 acts as a turn-off intensity-based indicator. Both fluorescent compounds bind the divalent zinc cation with micromolar affinity.National Institute of General Medical Sciences (U.S.) (grant GM065519
