A New Class of Isocyanide-Containing Rhenium(I) Bipyridyl Luminophore with Readily Tunable and Highly Environmentally Sensitive Excited-State Properties Chi-On Ng, † Larry Tso-Lun Lo, † Siu-Mui Ng, † Chi-Chiu Ko,* ,† and Nianyong Zhu ‡ Department of Biology and Chemistry, City UniVersity of Hong Kong, Tat Chee AVenue, Kowloon, Hong Kong, China, and Department of Chemistry, The UniVersity of Hong Kong, Pokfulam Road, Hong Kong, China Received May 18, 2008 A new class of readily tunable and highly environmentally sensitive luminescent rhenium(I) tetra(isocyano)bipyridyl complexes has been synthesized and characterized, and their luminescent properties have been investigated. Preliminary studies showed that the metal- to-ligand charge-transfer [dπ(Re) f π*(bpy)] absorption and emission are extremely sensitive to the nature of the solvent and the rigidity of the environment. Rhenium(I) bipyridylcarbonyl complexes have received considerable attention not only because of their rich excited- state chemistry but also because of the luminescence proper- ties associated with the metal-to-ligand charge-transfer (MLCT) excited state. 1 These compounds are also widely used as building blocks for many different applications, 2–4 such as photosensitizers, 2 photocatalysts, 3 solar energy converters, 3 and luminescent sensors and probes. 4 While rhenium(I) carbonylbipyridyl complexes have been exten- sively investigated, the isoelectronic rhenium(I) isocyano- bipyridyl complexes have not been explored. It is hypoth- esized that replacing the carbonyl ligands with isocyanide ligands would provide an additional means of tuning the ex- cited-state properties of the metal complex system because the electronic and steric properties of an isocyanide are readily tuned by the substituents attached to its N atom. 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Chem. 1983, 255, 345. Inorg. Chem. 2008, 47, 7447-7449 10.1021/ic800906x CCC: $40.75  2008 American Chemical Society Inorganic Chemistry, Vol. 47, No. 17, 2008 7447 Published on Web 07/29/2008