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Title: Photophysics and Luminescence Spectroelectrochemistry of [Tc(dmpe)3]+/2+ (dmpe = 1,2-bis(dimethylphosphino)ethane)

The ligand-to-metal charge transfer (LMCT) excited state luminescence of [Tc(dmpe)3]2+ (dmpe is 1,2-bis-(dimethylphosphino)ethane) has been measured in solution at room temperature, and is compared to its Re analogue. Surprisingly, both [M(dmpe)3]2+* (M = Re, Tc) 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); E1/2* = +2.61(2.48) V versus SCE; λmax = 526(585) nm). Open shell TDDFT calculations support the assignment of the lowest energy transition in both the technetium and rhenium complexes to be a doublet-doublet process that involve predominantly LMCT (dmpe-to-metal) character and is in agreement with past assignments for the Re system. As expected for highly oxidizing excited state potentials, quenching is observed for the excited states by both the rhenium and technetium complexes. Stern-Volmer analysis resulted in quenching parameters for both the rhenium and technetium complexes under identical conditions, and are compared using Rehm-Weller analysis. Of particular interest is the fact that both benzene and toluene are oxidized by both the Re and Tc systems.
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Publication Date:
OSTI Identifier:
Report Number(s):
24491a; 47615; 38994; 39193; KP1504010
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry A, 117(48):12749-12758
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
Country of Publication:
United States
technetium, rhenium, photophysics, photochemistry, spectroelectrochemistry, highly oxidizing excited states; Environmental Molecular Sciences Laboratory