Highly Oxidizing Excited States of Re and Tc Complexes

• Published in: Journal of the American Chemical Society Vol. 128; no. 51; pp. 16494 - 16495
• Main Authors: Del Negro, Andrew S, Seliskar, Carl J, Heineman, William R, Hightower, Sean E, Bryan, Samuel A, Sullivan, B. Patrick
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 27.12.2006
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Organometallic Compounds - chemistry; Oxidation-Reduction; Rhenium - chemistry; Technetium - chemistry; Technetium complexes; Oxidation; Transition element complexes; Rhenium complex; Excited state
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja067114g

Like the Re analogue, the ligand-to-metal charge transfer (LMCT) excited-state of [Tc(dmpe)3]2+ (dmpe is bis-1,2-(dimethylphosphino)ethane) is luminescent in solution at room temperature. Surprisingly, both [M(dmpe)3]2+* species have extremely large excited-state potentials (ESPs) as oxidantsthe highest for any simple coordination complex of a transition metal. Furthermore, this potential is available using a photon of visible light (calculated for M = Re(Tc); E 1/2* = +2.61(2.52) V versus SCE; λmax = 526(585) nm). Using a Rehm−Weller analysis with a series of aromatic hydrocarbons as electron-transfer quenchers, E 1/2(Re2+* /Re+) has been determined to be 2.58 V, in good agreement with the calculated value. Both [M(dmpe)3]2+* species are quenched by chloride ion and both can function as excited-state oxidants in water solution.