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A family of coumarin-enamine chemodosimeters is evaluated for their potential use as fluorescent molecular probes for multiple analytes [cadmium(II), cobalt(II), copper(II), iron(II), nickel(II), lead(II), and zinc(II)], as their chloride and acetate salts. These fluorophores displayed excellent optical spectroscopic modulation when exposed to ion pairs with different Lewis acidic and basic properties in dimethyl sulfoxide (DMSO). The chemodosimeters were designed to undergo excited-state intramolecular proton transfer (ESIPT), which leads to significant Stokes shifts (ca. 225 nm) and lower-energy fluorescence emission (ca. 575 nm). A more basic anion, e.g., acetate, inhibited the ESIPT mechanism by deprotonation of the enol, producing a binding pocket (N^O - chelate) that can coordinate to an appropriate metal ion. Coordination of the metal ions enhances the fluorescent intensity via the chelation-enhanced fluorescence emission mechanism. Subjecting the spectroscopic data to linear discriminant analysis provided insights into the source of these systems' markedly different behavior toward ion pairs, despite the subtle structural differences in the organic framework. These compounds are examples of versatile, low-molecular-weight, dual-channel fluorescent sensors for ion-pair recognition. This study paves the way for using these probes as practical components of a sensing array for different metal ions and their respective anions.

A silver thiazolylurea complex, [Ag(TUTh) 2 ] + , has been used as a host species for geometrically differently shaped mono- and dianions: trigonal planar (NO 3 - ), tetrahedral (SO 4 2- ), and octahedral (SiF 6 2- ). In the presence of nitrate a 1:1 near-planar tweezer host-guest species is formed, with poor binding in solution despite excellent geometric complementarity being found between the host and the anion in the solid state. In the presence of either SO 4 2- or SiF 6 2- a 2:1 host-guest species is formed, whereby the guest is held in a capsulelike arrangement stabilized by an array of eight NH hydrogen-bond donors, as confirmed by X-ray crystallographic studies. Solution studies in DMSO-d 6 support the host-guest stoichiometry seen in the solid state. The binding constant between SO 4 2- and [Ag(TUTh) 2 ] + was calculated to be K 21 = 2511 M -2 and was shown to be the dominant species in solution, in excellent agreement with the solid-state studies. However, upon the addition of SiF 6 2- ions different speciation is observed: H 2 ·G (capsule), H·G (tweezer), and H·G 2 during the course of the study.