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Phosphine and phosphonite complexes of a Ru(II) porphyrin. 2. Photophysical and electrochemical studies

Phosphine and phosphonite complexes of a Ru(II) porphyrin. 2. Photophysical and electrochemical studies
Phosphine and phosphonite complexes of a Ru(II) porphyrin. 2. Photophysical and electrochemical studies
The photophysical and electrochemical properties of a series of mono- and bis-phosphine complexes of a 5,15-diphenyl-substituted ruthenium porphyrin, (MeOH)Ru-II(CO)(DPP) 1, were investigated. The ligands used were diphenyl-(phenylacetenyl)phosphine (DPAP), diethyl (phenylacetenyl)phosphonite [PAP(OEt)(2)], tris(phenylacetenyl)phosphine [(PA)(3)P], and bis(diphenylphosphino)acetylene (DPPA). All complexes display two reversible one-electron oxidations at: 0.61 and 1.0 V vs SCE (1), 0.42-0.51 and 0,97-1.05 V [(PR3)Ru-II(CO)(DPP)], and 0.06-0.25 and 0.82-0.95 V [(PR3)(2)Ru-II(DPP)]. As predicted by EHMO calculations, the first oxidation is porphyrin or phosphorus centered, whereas the second one is ruthenium centered. Bulk electrolysis at the first oxidation potential yields stable monocations. Simulation of the cyclic voltammogram of (DPAP)Ru-II(CO)(DPP) in CH2Cl2 demonstrates the kinetic lability of the complex, and the association constant found (K = 1.27 x 10(6) M-1) is in accordance with the value determined by UV-vis titration (K = 1.2 +/- 0.3 x 10(6) M-1). Coordination of one phosphine ligand to Ru-II(CO)(DPP) leads to a red shift in both the absorption and luminescence spectra. Shifts are typically 10 nm for the B- and Q-band absorptions and are not affected by the nature of the phosphorus ligand. The intense luminescence of (PR3)Ru-II(CO)(DPP), red-shifted by 21-28 nm compared to 1, can be attributed to originate from a (3)(pi,pi*) excited state, and it exhibits lifetimes from 150 to 240 mus. In the bis-phosphine complexes (PR3)(2)Ru-II(DPP), the Q-band absorption is broadened and does not show any distinct peak. Judged from EHMO calculation, this could arise from a low-energy charge-transfer state involving the phosphorus ligand. The luminescence is efficiently quenched due to radiationless decay from a charge-transfer excited state, involving either the metal center or the phosphorus ligand; an unambiguous assignment could not be made.
excited-states, ruthenium porphyrins, redox chemistry, axial-ligand, metalloporphyrin, octaethylporphyrin, ligation site
0020-1669
5269-5275
Stulz, Eugen
9a6c04cf-32ca-442b-9281-bbf3d23c622d
Sanders, Jeremy K.M.
a676d635-3196-437a-b894-a2bc5f857ae2
Montalti, Marco
1ed31a39-9b5d-4ec1-88a5-11ca6a58714a
Prodi, Luca
ee06a3a3-cc22-4db3-9805-5f395230c353
Zaccheroni, Nelsi
cea8a96e-3774-458c-b56e-33e60cb26f26
de Biani, Fabrizia
e1d52ced-d954-47bb-8564-67a507eec08c
Grigiotti, Emanuela
50bf7640-56f7-41e0-b640-5548c563492e
Zanello, Piero
260f8bb4-4b43-457e-9d50-c341179c5646
Stulz, Eugen
9a6c04cf-32ca-442b-9281-bbf3d23c622d
Sanders, Jeremy K.M.
a676d635-3196-437a-b894-a2bc5f857ae2
Montalti, Marco
1ed31a39-9b5d-4ec1-88a5-11ca6a58714a
Prodi, Luca
ee06a3a3-cc22-4db3-9805-5f395230c353
Zaccheroni, Nelsi
cea8a96e-3774-458c-b56e-33e60cb26f26
de Biani, Fabrizia
e1d52ced-d954-47bb-8564-67a507eec08c
Grigiotti, Emanuela
50bf7640-56f7-41e0-b640-5548c563492e
Zanello, Piero
260f8bb4-4b43-457e-9d50-c341179c5646

Stulz, Eugen, Sanders, Jeremy K.M., Montalti, Marco, Prodi, Luca, Zaccheroni, Nelsi, de Biani, Fabrizia, Grigiotti, Emanuela and Zanello, Piero (2002) Phosphine and phosphonite complexes of a Ru(II) porphyrin. 2. Photophysical and electrochemical studies. Inorganic Chemistry, 41 (20), 5269-5275. (doi:10.1021/ic025728q).

Record type: Article

Abstract

The photophysical and electrochemical properties of a series of mono- and bis-phosphine complexes of a 5,15-diphenyl-substituted ruthenium porphyrin, (MeOH)Ru-II(CO)(DPP) 1, were investigated. The ligands used were diphenyl-(phenylacetenyl)phosphine (DPAP), diethyl (phenylacetenyl)phosphonite [PAP(OEt)(2)], tris(phenylacetenyl)phosphine [(PA)(3)P], and bis(diphenylphosphino)acetylene (DPPA). All complexes display two reversible one-electron oxidations at: 0.61 and 1.0 V vs SCE (1), 0.42-0.51 and 0,97-1.05 V [(PR3)Ru-II(CO)(DPP)], and 0.06-0.25 and 0.82-0.95 V [(PR3)(2)Ru-II(DPP)]. As predicted by EHMO calculations, the first oxidation is porphyrin or phosphorus centered, whereas the second one is ruthenium centered. Bulk electrolysis at the first oxidation potential yields stable monocations. Simulation of the cyclic voltammogram of (DPAP)Ru-II(CO)(DPP) in CH2Cl2 demonstrates the kinetic lability of the complex, and the association constant found (K = 1.27 x 10(6) M-1) is in accordance with the value determined by UV-vis titration (K = 1.2 +/- 0.3 x 10(6) M-1). Coordination of one phosphine ligand to Ru-II(CO)(DPP) leads to a red shift in both the absorption and luminescence spectra. Shifts are typically 10 nm for the B- and Q-band absorptions and are not affected by the nature of the phosphorus ligand. The intense luminescence of (PR3)Ru-II(CO)(DPP), red-shifted by 21-28 nm compared to 1, can be attributed to originate from a (3)(pi,pi*) excited state, and it exhibits lifetimes from 150 to 240 mus. In the bis-phosphine complexes (PR3)(2)Ru-II(DPP), the Q-band absorption is broadened and does not show any distinct peak. Judged from EHMO calculation, this could arise from a low-energy charge-transfer state involving the phosphorus ligand. The luminescence is efficiently quenched due to radiationless decay from a charge-transfer excited state, involving either the metal center or the phosphorus ligand; an unambiguous assignment could not be made.

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Published date: 2002
Keywords: excited-states, ruthenium porphyrins, redox chemistry, axial-ligand, metalloporphyrin, octaethylporphyrin, ligation site

Identifiers

Local EPrints ID: 41077
URI: http://eprints.soton.ac.uk/id/eprint/41077
ISSN: 0020-1669
PURE UUID: 5a9a17fa-19a9-4dea-816b-9f422c5e679d
ORCID for Eugen Stulz: ORCID iD orcid.org/0000-0002-5302-2276

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Date deposited: 14 Jul 2006
Last modified: 27 Jul 2022 01:41

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Contributors

Author: Eugen Stulz ORCID iD
Author: Jeremy K.M. Sanders
Author: Marco Montalti
Author: Luca Prodi
Author: Nelsi Zaccheroni
Author: Fabrizia de Biani
Author: Emanuela Grigiotti
Author: Piero Zanello

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