A rhenium(I) tricarbonyl complex with a 3-(pyridin-2-yl)pyrazole chromophoric ligand and a functionalized organosilane spectator ligand, [Re(py-pzH)(CO) 3 (L 1 )](CF 3 SO 3 ) (1) [where py-pzH~3-(pyridin-2-yl)pyrazole, L 1 ~3-N-(pyridin-4-ylmethylene)aminopropyltriethoxysilane], as well as its analog, [Re(py-pzH)(CO) 3 (py)](CF 3 SO 3 ) (2) (where py~pyridine) have been synthesized. The room temperature MLCT luminescence properties of 1 and 2 (l max at 484 and 489 nm, respectively) were found to be sensitive to the protonation±deprotonation status of the 3-(pyridin-2-yl)pyrazole ligand. Spectro¯uorometric pH titration of 2 in aqueous media revealed an excited state pK a of 7.05. Sol±gel material formed from hydrolysis of 1 was successfully spin-coated onto glass microscope slides. The result was a sol±gel based luminescent pH sensor capable of responding over a wide pH range from pH 2.3 to 12 in air. The applicability of the principle of direct perturbation of electronic factors of sensor molecules in the development of luminescent chemical sensing materials is demonstrated.

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Luminescent properties of the supramolecular complex, [Re(bpy 1), with two adjacent dimethyl malonate moieties joined together by a pyridine substituted methylene bridge, are found to respond selectively to Ba 2þ upon deprotonation of the two malonate moieties.