Photophysical properties of covalently attached Ru(bpy)3 2+ and mcyclam2+ (M = Ni, H2) complexes

Etsuko Fujita, Steven J. Milder, Bruce S. Brunschwig

Research output: Contribution to journalArticle

42 Citations (Scopus)

Abstract

Absorption and emission spectra, emission quantum yields, and excited-state lifetimes of the metal-to-ligand charge-transfer (MLCT) excited state(s) of Ru(bpy)2(6-Mebpy)2+, Ru(bpy)2(bpy-cyclamH2)4+, and Ru(bpy)2(bpy-cyclamNi)4+ are reported. The absorption and emission spectra of these complexes are similar to those of Ru(bpy)3 2+ in H2O at room temperature except for small shifts in the maxima. The emission lifetime decreases by a factor of about 80 for 6-Mebpy, and the emission quantum yield decreases by a factor of about 300 for the bpy-cyclam pendant complexes as compared to the parent Ru(bpy)3 2+ complex at 25 °C. Decay of the 3MLCT excited state takes place by two independent channels: a temperature-independent pathway to the ground state and a thermally-activated pathway via a ligand-field excited state. Activation free energies, Ea, for the latter pathway were obtained from fits of the temperature-dependent emission lifetime measurements. Smaller Ea were observed for the 6-substituted complexes (1500-2300 cm-1) relative to Ru(bpy)3 2+ (3000-3910 cm-1) in EtOH and CH3CN, indicating that either the energy difference decreases and/or the reorganization parameter changes between the emissive 3MLCT and the ligand-field state to which it is strongly coupled. The smaller Ea can be attributed to the increased Ru-N bond distance in the 6-substituted complexes caused by steric hindrance that decreases the ligand-field strength and lowers the energy and/or reorganization parameter of the ligand-field excited state. For the bpy-cyclamNi2+ pendant complex, an energy-transfer pathway may also provide a deactivation channel.

Original languageEnglish
Pages (from-to)2079-2085
Number of pages7
JournalInorganic Chemistry
Volume31
Issue number11
Publication statusPublished - 1992

Fingerprint

Excited states
Ligands
ligands
excitation
Quantum yield
life (durability)
emission spectra
absorption spectra
deactivation
Energy transfer
Temperature
Ground state
Free energy
Charge transfer
field strength
Metals
Chemical activation
energy transfer
free energy
charge transfer

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Photophysical properties of covalently attached Ru(bpy)3 2+ and mcyclam2+ (M = Ni, H2) complexes. / Fujita, Etsuko; Milder, Steven J.; Brunschwig, Bruce S.

In: Inorganic Chemistry, Vol. 31, No. 11, 1992, p. 2079-2085.

Research output: Contribution to journalArticle

Fujita, Etsuko ; Milder, Steven J. ; Brunschwig, Bruce S. / Photophysical properties of covalently attached Ru(bpy)3 2+ and mcyclam2+ (M = Ni, H2) complexes. In: Inorganic Chemistry. 1992 ; Vol. 31, No. 11. pp. 2079-2085.
@article{37dcdc42286242a385e8bc12561522cd,
title = "Photophysical properties of covalently attached Ru(bpy)3 2+ and mcyclam2+ (M = Ni, H2) complexes",
abstract = "Absorption and emission spectra, emission quantum yields, and excited-state lifetimes of the metal-to-ligand charge-transfer (MLCT) excited state(s) of Ru(bpy)2(6-Mebpy)2+, Ru(bpy)2(bpy-cyclamH2)4+, and Ru(bpy)2(bpy-cyclamNi)4+ are reported. The absorption and emission spectra of these complexes are similar to those of Ru(bpy)3 2+ in H2O at room temperature except for small shifts in the maxima. The emission lifetime decreases by a factor of about 80 for 6-Mebpy, and the emission quantum yield decreases by a factor of about 300 for the bpy-cyclam pendant complexes as compared to the parent Ru(bpy)3 2+ complex at 25 °C. Decay of the 3MLCT excited state takes place by two independent channels: a temperature-independent pathway to the ground state and a thermally-activated pathway via a ligand-field excited state. Activation free energies, Ea, for the latter pathway were obtained from fits of the temperature-dependent emission lifetime measurements. Smaller Ea were observed for the 6-substituted complexes (1500-2300 cm-1) relative to Ru(bpy)3 2+ (3000-3910 cm-1) in EtOH and CH3CN, indicating that either the energy difference decreases and/or the reorganization parameter changes between the emissive 3MLCT and the ligand-field state to which it is strongly coupled. The smaller Ea can be attributed to the increased Ru-N bond distance in the 6-substituted complexes caused by steric hindrance that decreases the ligand-field strength and lowers the energy and/or reorganization parameter of the ligand-field excited state. For the bpy-cyclamNi2+ pendant complex, an energy-transfer pathway may also provide a deactivation channel.",
author = "Etsuko Fujita and Milder, {Steven J.} and Brunschwig, {Bruce S.}",
year = "1992",
language = "English",
volume = "31",
pages = "2079--2085",
journal = "Inorganic Chemistry",
issn = "0020-1669",
publisher = "American Chemical Society",
number = "11",

}

TY - JOUR

T1 - Photophysical properties of covalently attached Ru(bpy)3 2+ and mcyclam2+ (M = Ni, H2) complexes

AU - Fujita, Etsuko

AU - Milder, Steven J.

AU - Brunschwig, Bruce S.

PY - 1992

Y1 - 1992

N2 - Absorption and emission spectra, emission quantum yields, and excited-state lifetimes of the metal-to-ligand charge-transfer (MLCT) excited state(s) of Ru(bpy)2(6-Mebpy)2+, Ru(bpy)2(bpy-cyclamH2)4+, and Ru(bpy)2(bpy-cyclamNi)4+ are reported. The absorption and emission spectra of these complexes are similar to those of Ru(bpy)3 2+ in H2O at room temperature except for small shifts in the maxima. The emission lifetime decreases by a factor of about 80 for 6-Mebpy, and the emission quantum yield decreases by a factor of about 300 for the bpy-cyclam pendant complexes as compared to the parent Ru(bpy)3 2+ complex at 25 °C. Decay of the 3MLCT excited state takes place by two independent channels: a temperature-independent pathway to the ground state and a thermally-activated pathway via a ligand-field excited state. Activation free energies, Ea, for the latter pathway were obtained from fits of the temperature-dependent emission lifetime measurements. Smaller Ea were observed for the 6-substituted complexes (1500-2300 cm-1) relative to Ru(bpy)3 2+ (3000-3910 cm-1) in EtOH and CH3CN, indicating that either the energy difference decreases and/or the reorganization parameter changes between the emissive 3MLCT and the ligand-field state to which it is strongly coupled. The smaller Ea can be attributed to the increased Ru-N bond distance in the 6-substituted complexes caused by steric hindrance that decreases the ligand-field strength and lowers the energy and/or reorganization parameter of the ligand-field excited state. For the bpy-cyclamNi2+ pendant complex, an energy-transfer pathway may also provide a deactivation channel.

AB - Absorption and emission spectra, emission quantum yields, and excited-state lifetimes of the metal-to-ligand charge-transfer (MLCT) excited state(s) of Ru(bpy)2(6-Mebpy)2+, Ru(bpy)2(bpy-cyclamH2)4+, and Ru(bpy)2(bpy-cyclamNi)4+ are reported. The absorption and emission spectra of these complexes are similar to those of Ru(bpy)3 2+ in H2O at room temperature except for small shifts in the maxima. The emission lifetime decreases by a factor of about 80 for 6-Mebpy, and the emission quantum yield decreases by a factor of about 300 for the bpy-cyclam pendant complexes as compared to the parent Ru(bpy)3 2+ complex at 25 °C. Decay of the 3MLCT excited state takes place by two independent channels: a temperature-independent pathway to the ground state and a thermally-activated pathway via a ligand-field excited state. Activation free energies, Ea, for the latter pathway were obtained from fits of the temperature-dependent emission lifetime measurements. Smaller Ea were observed for the 6-substituted complexes (1500-2300 cm-1) relative to Ru(bpy)3 2+ (3000-3910 cm-1) in EtOH and CH3CN, indicating that either the energy difference decreases and/or the reorganization parameter changes between the emissive 3MLCT and the ligand-field state to which it is strongly coupled. The smaller Ea can be attributed to the increased Ru-N bond distance in the 6-substituted complexes caused by steric hindrance that decreases the ligand-field strength and lowers the energy and/or reorganization parameter of the ligand-field excited state. For the bpy-cyclamNi2+ pendant complex, an energy-transfer pathway may also provide a deactivation channel.

UR - http://www.scopus.com/inward/record.url?scp=33751391643&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33751391643&partnerID=8YFLogxK

M3 - Article

VL - 31

SP - 2079

EP - 2085

JO - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 11

ER -