Probing the use of long lived intra-ligand π–π* excited states for photocatalytic systems: A study of the photophysics and photochemistry of [ReCl(CO)3(dppz-(CH3)2)]

Peter A. Summers; James A. Calladine; Nasiru Ibrahim; Kennedy P. Kusumo; Charlotte A. Clark; Xue Z. Sun; Michelle L. Hamilton; Michael Towrie; Jonathan McMaster; Martin Schroder; Michael W. George

doi:10.1016/j.poly.2016.11.005

Probing the use of long lived intra-ligand π–π^* excited states for photocatalytic systems: A study of the photophysics and photochemistry of [ReCl(CO)₃(dppz-(CH₃)₂)]

Peter A. Summers^*, James A. Calladine, Nasiru Ibrahim, Kennedy P. Kusumo, Charlotte A. Clark, Xue Z. Sun, Michelle L. Hamilton, Michael Towrie, Jonathan McMaster, Martin Schroder, Michael W. George

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

We report the excited state photophysics and photochemistry of [ReCl(CO)₃(dppz-(CH₃)₂)] (dppz-(CH₃)₂ = 11,12-dimethyl-dipyrido[3,2-a:2′,3′-c]phenazine) in CH₃CN using time-resolved infrared (TRIR) and Fourier transform infrared (FTIR) spectroscopy. Excitation of the ¹MLCT (metal-to-ligand charge transfer) band of [ReCl(CO)₃(dppz-(CH₃)₂)] populates a ³MLCT excited state which rapidly interconverts on a timescale <1 ns to a long lived IL (intra-ligand) ππ^∗ excited state with a lifetime of 190 ( ± 5) ns. In the presence of an electron donor (NEt₃), the IL excited state of [ReCl(CO)₃(dppz-(CH₃)₂)] can be reductively quenched to [ReCl(CO)₃(dppz-(CH₃)₂)]⁻ with the radical in the latter localised on the distal phenazine (phz) portion of the dppz ligand. The phz based electron in [ReCl(CO)₃(dppz-(CH₃)₂)]⁻ has minimal interaction with the rhenium metal centre which increases the stability of the photosensitiser in its reduced form. In non-dried, non-degassed CH₃CN (1 M NEt₃), [ReCl(CO)₃(dppz-(CH₃)₂)]⁻ shows no significant change in the carbonyl region of the IR spectrum for at least 2 h during continuous photolysis. In addition, we investigate the use of [ReCl(CO)₃(dppz-(CH₃)₂)]⁻ to reduce the previously studied catalyst [NiFe₂], with facile electron transfer from [ReCl(CO)₃(dppz-(CH₃)₂)]⁻ to form [NiFe₂]⁻.

Original language	English
Pages (from-to)	259-264
Number of pages	6
Journal	Polyhedron
Volume	123
Early online date	12 Nov 2016
DOIs	https://doi.org/10.1016/j.poly.2016.11.005
Publication status	Published - 17 Feb 2017

Keywords

Intra-ligand excited state
Photophysics
Reductive quenching
Rhenium
Time-resolved IR

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10.1016/j.poly.2016.11.005

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Summers, P. A., Calladine, J. A., Ibrahim, N., Kusumo, K. P., Clark, C. A., Sun, X. Z., Hamilton, M. L., Towrie, M., McMaster, J., Schroder, M., & George, M. W. (2017). Probing the use of long lived intra-ligand π–π^* excited states for photocatalytic systems: A study of the photophysics and photochemistry of [ReCl(CO)₃(dppz-(CH₃)₂)]. Polyhedron, 123, 259-264. https://doi.org/10.1016/j.poly.2016.11.005

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title = "Probing the use of long lived intra-ligand π–π* excited states for photocatalytic systems: A study of the photophysics and photochemistry of [ReCl(CO)3(dppz-(CH3)2)]",

abstract = "We report the excited state photophysics and photochemistry of [ReCl(CO)3(dppz-(CH3)2)] (dppz-(CH3)2 = 11,12-dimethyl-dipyrido[3,2-a:2′,3′-c]phenazine) in CH3CN using time-resolved infrared (TRIR) and Fourier transform infrared (FTIR) spectroscopy. Excitation of the 1MLCT (metal-to-ligand charge transfer) band of [ReCl(CO)3(dppz-(CH3)2)] populates a 3MLCT excited state which rapidly interconverts on a timescale <1 ns to a long lived IL (intra-ligand) ππ∗ excited state with a lifetime of 190 ( ± 5) ns. In the presence of an electron donor (NEt3), the IL excited state of [ReCl(CO)3(dppz-(CH3)2)] can be reductively quenched to [ReCl(CO)3(dppz-(CH3)2)]− with the radical in the latter localised on the distal phenazine (phz) portion of the dppz ligand. The phz based electron in [ReCl(CO)3(dppz-(CH3)2)]− has minimal interaction with the rhenium metal centre which increases the stability of the photosensitiser in its reduced form. In non-dried, non-degassed CH3CN (1 M NEt3), [ReCl(CO)3(dppz-(CH3)2)]− shows no significant change in the carbonyl region of the IR spectrum for at least 2 h during continuous photolysis. In addition, we investigate the use of [ReCl(CO)3(dppz-(CH3)2)]− to reduce the previously studied catalyst [NiFe2], with facile electron transfer from [ReCl(CO)3(dppz-(CH3)2)]− to form [NiFe2]−.",

keywords = "Intra-ligand excited state, Photophysics, Reductive quenching, Rhenium, Time-resolved IR",

author = "Summers, {Peter A.} and Calladine, {James A.} and Nasiru Ibrahim and Kusumo, {Kennedy P.} and Clark, {Charlotte A.} and Sun, {Xue Z.} and Hamilton, {Michelle L.} and Michael Towrie and Jonathan McMaster and Martin Schroder and George, {Michael W.}",

year = "2017",

month = feb,

day = "17",

doi = "10.1016/j.poly.2016.11.005",

language = "English",

volume = "123",

pages = "259--264",

journal = "Polyhedron",

issn = "0277-5387",

publisher = "Elsevier BV",

}

Summers, PA, Calladine, JA, Ibrahim, N, Kusumo, KP, Clark, CA, Sun, XZ, Hamilton, ML, Towrie, M, McMaster, J, Schroder, M & George, MW 2017, 'Probing the use of long lived intra-ligand π–π^* excited states for photocatalytic systems: A study of the photophysics and photochemistry of [ReCl(CO)₃(dppz-(CH₃)₂)]', Polyhedron, vol. 123, pp. 259-264. https://doi.org/10.1016/j.poly.2016.11.005

TY - JOUR

T1 - Probing the use of long lived intra-ligand π–π* excited states for photocatalytic systems

T2 - A study of the photophysics and photochemistry of [ReCl(CO)3(dppz-(CH3)2)]

AU - Summers, Peter A.

AU - Calladine, James A.

AU - Ibrahim, Nasiru

AU - Kusumo, Kennedy P.

AU - Clark, Charlotte A.

AU - Sun, Xue Z.

AU - Hamilton, Michelle L.

AU - Towrie, Michael

AU - McMaster, Jonathan

AU - Schroder, Martin

AU - George, Michael W.

PY - 2017/2/17

Y1 - 2017/2/17

N2 - We report the excited state photophysics and photochemistry of [ReCl(CO)3(dppz-(CH3)2)] (dppz-(CH3)2 = 11,12-dimethyl-dipyrido[3,2-a:2′,3′-c]phenazine) in CH3CN using time-resolved infrared (TRIR) and Fourier transform infrared (FTIR) spectroscopy. Excitation of the 1MLCT (metal-to-ligand charge transfer) band of [ReCl(CO)3(dppz-(CH3)2)] populates a 3MLCT excited state which rapidly interconverts on a timescale <1 ns to a long lived IL (intra-ligand) ππ∗ excited state with a lifetime of 190 ( ± 5) ns. In the presence of an electron donor (NEt3), the IL excited state of [ReCl(CO)3(dppz-(CH3)2)] can be reductively quenched to [ReCl(CO)3(dppz-(CH3)2)]− with the radical in the latter localised on the distal phenazine (phz) portion of the dppz ligand. The phz based electron in [ReCl(CO)3(dppz-(CH3)2)]− has minimal interaction with the rhenium metal centre which increases the stability of the photosensitiser in its reduced form. In non-dried, non-degassed CH3CN (1 M NEt3), [ReCl(CO)3(dppz-(CH3)2)]− shows no significant change in the carbonyl region of the IR spectrum for at least 2 h during continuous photolysis. In addition, we investigate the use of [ReCl(CO)3(dppz-(CH3)2)]− to reduce the previously studied catalyst [NiFe2], with facile electron transfer from [ReCl(CO)3(dppz-(CH3)2)]− to form [NiFe2]−.

AB - We report the excited state photophysics and photochemistry of [ReCl(CO)3(dppz-(CH3)2)] (dppz-(CH3)2 = 11,12-dimethyl-dipyrido[3,2-a:2′,3′-c]phenazine) in CH3CN using time-resolved infrared (TRIR) and Fourier transform infrared (FTIR) spectroscopy. Excitation of the 1MLCT (metal-to-ligand charge transfer) band of [ReCl(CO)3(dppz-(CH3)2)] populates a 3MLCT excited state which rapidly interconverts on a timescale <1 ns to a long lived IL (intra-ligand) ππ∗ excited state with a lifetime of 190 ( ± 5) ns. In the presence of an electron donor (NEt3), the IL excited state of [ReCl(CO)3(dppz-(CH3)2)] can be reductively quenched to [ReCl(CO)3(dppz-(CH3)2)]− with the radical in the latter localised on the distal phenazine (phz) portion of the dppz ligand. The phz based electron in [ReCl(CO)3(dppz-(CH3)2)]− has minimal interaction with the rhenium metal centre which increases the stability of the photosensitiser in its reduced form. In non-dried, non-degassed CH3CN (1 M NEt3), [ReCl(CO)3(dppz-(CH3)2)]− shows no significant change in the carbonyl region of the IR spectrum for at least 2 h during continuous photolysis. In addition, we investigate the use of [ReCl(CO)3(dppz-(CH3)2)]− to reduce the previously studied catalyst [NiFe2], with facile electron transfer from [ReCl(CO)3(dppz-(CH3)2)]− to form [NiFe2]−.

KW - Intra-ligand excited state

KW - Photophysics

KW - Reductive quenching

KW - Rhenium

KW - Time-resolved IR

UR - http://www.scopus.com/inward/record.url?scp=85007302222&partnerID=8YFLogxK

U2 - 10.1016/j.poly.2016.11.005

DO - 10.1016/j.poly.2016.11.005

M3 - Article

AN - SCOPUS:85007302222

SN - 0277-5387

VL - 123

SP - 259

EP - 264

JO - Polyhedron

JF - Polyhedron

ER -

Probing the use of long lived intra-ligand π–π^* excited states for photocatalytic systems: A study of the photophysics and photochemistry of [ReCl(CO)₃(dppz-(CH₃)₂)]

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