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Synthesis, Structures, and Optical Properties of Ruthenium(II) Complexes of the Tris(1-pyrazolyl)methane Ligand

Coe, Benjamin J. and Helliwell, Madeleine and Peers, Martyn K. and Raftery, James and Rusanova, Daniela and Clays, Koen and Depotter, Griet and Brunschwig, Bruce S. (2014) Synthesis, Structures, and Optical Properties of Ruthenium(II) Complexes of the Tris(1-pyrazolyl)methane Ligand. Inorganic Chemistry, 53 (7). pp. 3798-3811. ISSN 0020-1669.

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Four new complex salts [Ru^(II)Cl(Tpm)(L^A)_2][PF_6]_n [Tpm = tris(1-pyrazolyl)methane; n = 1, L^A = pyridine (py) 1 or ethyl isonicotinate (EIN) 2; n = 3, L^A = N-methyl-4,4′-bipyridinium (MeQ^+) 3 or N-phenyl-4,4′-bipyridinium (PhQ^+) 4] have been prepared and characterized. Electronic absorption spectra show intense d → π^* metal-to-ligand charge-transfer (MLCT) absorption bands, while cyclic voltammetry reveals a reversible Ru^(III/II) wave, accompanied by quasireversible or irreversible L^A-based reductions for all except 1. Single crystal X-ray structures have been obtained for 1•Me_2CO, 2, and 3•Me_2CO. For 2–4, molecular first hyperpolarizabilities β have been measured in acetonitrile solutions via the hyper-Rayleigh scattering (HRS) technique at 800 nm. Stark (electroabsorption) spectroscopic studies on the MLCT bands in frozen butyronitrile allow the indirect estimation of static first hyperpolarizabilities β_0. The various physical data obtained for 3 and 4 are compared with those reported previously for related cis-{Ru^(II)(NH_3)_4}^(2+) species [Coe, B. J. et al. J. Am. Chem. Soc. 2005, 127, 4845]. TD-DFT calculations on the complexes in 1–4 confirm that their lowest energy absorption bands are primarily Ru^(II) → L^A MLCT in character, while Ru^(II) → Tpm MLCT transitions are predicted at higher energies. DFT agrees with the Stark, but not the HRS measurements, in showing that β_0 increases with the electron-accepting strength of L^A. The 2D nature of the chromophores is evidenced by dominant β_(xxy) tensor components.

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URLURL TypeDescription Information
Coe, Benjamin J.0000-0002-5998-3895
Brunschwig, Bruce S.0000-0002-6135-6727
Additional Information:© 2014 American Chemical Society. Received: January 21, 2014. Published: March 10, 2014. Published In Issue April 07, 2014. We thank the EPSRC for support (grant EP/G02099) and also the Fund for Scientific Research-Flanders (FWO-V, G.0312.08) and the University of Leuven (GOA/2011/03). B.S.B. acknowledges the Beckman Institute of the California Institute of Technology for support. We are grateful to James Amphlett (Manchester) for assistance with the purification of complex salt 3 and to Nick Van Steerteghem (Leuven) for help with the HRS experiments.
Funding AgencyGrant Number
Engineering and Physical Sciences Research Council (EPSRC)EP/G02099
Fonds Wetenschappelijk Onderzoek - Vlaanderen (FWO)G.0312.08
University of LeuvenGOA/2011/03
Caltech Beckman InstituteUNSPECIFIED
Issue or Number:7
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Official Citation:Synthesis, Structures, and Optical Properties of Ruthenium(II) Complexes of the Tris(1-pyrazolyl)methane Ligand Benjamin J. Coe, Madeleine Helliwell, Martyn K. Peers, James Raftery, Daniela Rusanova, Koen Clays, Griet Depotter, and Bruce S. Brunschwig Inorganic Chemistry 2014 53 (7), 3798-3811
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46089
Deposited By: Ruth Sustaita
Deposited On:05 Jun 2014 16:33
Last Modified:03 Oct 2019 06:40

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