Lanthanide(III) bent-metallocene complexes with a novel photofunctionalized pentamethylcyclopentadienyl ligand having an N-phenylcarbazolyl group (Cp PhCar =η 5 -C 5 Me 4 CH 2 -C 18 H 12 N), [Ln(Cp PhCar ) 2 I(THF)] (Ln = Tb (1), Gd (2)), were prepared and their molecular structures and luminescence properties were investigated. The f-f emission from the terbium metal center of 1 was efficiently sensitized by Cp PhCar (ε=0.88 Â 10 4 M -1 cm -1 at 331 nm, Φ = 0.67 at 330 nm excitation, k r = 1.68Â10 3 s -1 ). Additionally, the solid-state structure of potassium salts of C 5 -ring (η 5 -C 5 R 5 , R = Me, H) derivatives was uncommonly characterized in Cp PhCar .Ligand functionalization is a common approach to form metal complexes that have a desired structure and functionality. To date, various photofunctionalized ligands have been developed and successfully utilized as photosensitizers for transition-metal and lanthanide complexes. 1 Among them, macrocyclic polyamines such as cyclam (1,4,8,11-tetraazacyclotetradecane) and tacn (1,4,7-triazacyclononane), which are popular ligands in inorganic chemistry, are widely employed as useful frameworks to construct adaptable and efficient photofunctionalized ligands. 2,3 Although the anionic pentamethylcyclopentadienyl ligand (Cp* = η 5 -C 5 Me 5 ) is one of the most common and important ligands in organometallic chemistry, 4 photofunctionalized Cp* derivatives have been hitherto unknown because of troublesome synthesis and isolation of the ligand. 5 We believe that photofunctionalized Cp* ligands could open a new field of organometallic chemistry, including developments of novel photocatalysts and luminous materials. We have now found that a new class of photofunctionalized ligands, the N-phenylcarbazolyl-functionalized Cp* ligand (Cp PhCar = η 5 -C 5 Me 4 CH 2 C 18 H 12 N), serves as an efficient photosensitizer for the terbium(III) ion. Thus, a highly luminescent organolanthanide complex having a fast radiation rate was successfully prepared by proper combination of the metal ion and the photofunctionalized Cp* ligand (vide infra). Herein we report the synthesis, structure, and photophysical properties of a terbium(III) complex with Cp PhCar , [Tb(Cp PhCar ) 2 I(THF)] (1). The gadolinium(III) complex [Gd(Cp PhCar ) 2 I(THF)] (2) was also synthesized to gain insight into the photosensitization of the N-phenylcarbazolyl group. Furthermore, the solid-state polymeric structure of the THF-solvated Cp PhCar potassium salt, which is a key precursor for the preparation of 1 and 2, is presented. Solidstate structural information for the Cp* or Cp (η 5 -C 5 H 5 ) derivative alkali-metal salts is comparatively limited, even though their salts are widely used for preparing organometallic complexes. 4a,6 Quici, S.; Barigelletti, F.; Accorsi, G.; Bottaro, G.; Cavazzini, M.; Tondello, E. Coord. Chem. Rev. 2010, 254, 487. (2) (a) Prodi, L.; Maestri, M.; Ziessel, R.; Balzani, V. Inorg. Chem. 1991, 30, 3798. (b) Alexander, V. Chem. Rev. 1995, 95, 273. (c) DeRosa, F.; Bu, X.; Ford, P. C. I...