Intersystem crossing to both ligand-localized and charge-transfer excited states in mononuclear and dinuclear ruthenium(II) diimine complexes

Shaw, John R.; Webb, Ralph T.; Schmehl, Russell H.

doi:10.1021/ja00159a035

Cited by 101 publications

(68 citation statements)

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“…This situation would arise if a higher-energy triplet state promotes rapid nonradiative deactivation to the ground state provided the two states are in equilibrium at 77 K. This higherenergy excited state is tentatively assigned to a π,π* triplet state localized on the ditopic ligand. 30,31 However, the MLCT triplet associated with the parent ligand is situated between these triplets and might contribute to the overall deactivation process.…”

Section: Discussionmentioning

confidence: 99%

Electron Delocalization in Ruthenium(II) and Osmium(II) 2,2‘-Bipyridyl Complexes Formed from Ethynyl-Bridged Ditopic Ligands

et al. 1996

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Photophysical and electrochemical properties have been recorded for a series of mono-and binuclear ruthenium-(II) and osmium(II) 2,2′-bipyridyl complexes that contain an ethynyl-bridged ditopic ligand. In particular, the electrochemical properties are indicative of electron delocalization over an extended π*-orbital in the π-radical anions. The site of attachment of the ethynyl substituent to the 2,2′-bipyridyl ring affects the various properties, especially absorption and emission spectral maxima. In most cases, the rates of nonradiative deactivation of the lowest-energy triplet excited states are slower than expected for a corresponding complex not possessing a conjugated substituent. This effect is rationalized in terms of electron delocalization over part of the ditopic ligand within the triplet state and its significance depends markedly on the triplet energy of the complex in question. The lowest-energy triplet mixes to some extent with an upper-lying triplet that is more strongly coupled to the ground state. According to the nature of the metal complex, this higherenergy triplet might originate from (i) charge transfer from metal center to parent ligand, (ii) a π,π* state localized on the ditopic ligand, or (iii) a metal-centered excited state. For the Os II complexes at 77 K electron delocalization over an extended π*-orbital is accompanied by a reduction in the amount of nuclear displacement between triplet and ground states and by a smaller vibronic coupling matrix element relative to the parent complex. These two factors combine, within the framework of the energy-gap law, to decrease the rate at which electronic energy can be dissipated among medium-frequency vibrational (i.e., -CdC-and -CdN-) modes. This realization permits a quantitative explanation of the measured rate constants for nonradiative decay of the triplet excited states of these ethynyl-substituted metal complexes.

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Section: Discussionmentioning

confidence: 99%

Electron Delocalization in Ruthenium(II) and Osmium(II) 2,2‘-Bipyridyl Complexes Formed from Ethynyl-Bridged Ditopic Ligands

et al. 1996

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“…The trans!cis isomerization of coordinated stpy has been shown to take place from a 3 IL excited state localized at the stpy ligand, which is populated from a Re(CO) 3 !bpy 3 MLCT state by ultrafast (3.5 ps), intramolecular energy transfer. This kind of "intramolecular sensitization" of intraligand photochemistry by MLCT excitation, [13,[36][37][38][39][40][41] the kinetics of which were first determined [23] for [ReA C H T U N G T R E N N U N G (stpy)(CO) 3 A C H T U N G T R E N N U N G (bpy)] + , opens interesting possibilities in designing new molecular photonic switches and sensors. [11] Herein, we introduce these photoreactive properties in two new complexes [Re(Cl)(CO) 3 Figure 1) and investigate their redox properties, photochemistry, and excited-state dynamics.…”

Section: A C H T U N G T R E N N U N G (Bpy)]mentioning

confidence: 99%

Ultrafast Excited State Dynamics Controlling Photochemical Isomerization of N‐Methyl‐4‐[trans‐2‐(4‐pyridyl)ethenyl]pyridinium Coordinated to a {Re^I(CO)₃(2,2′‐bipyridine)} Chromophore

Hartl

Matousek

Towrie

et al. 2008

Chemistry A European J

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Two multifunctional photoactive complexes [Re(Cl)(CO)(3)(MeDpe(+))(2)](2+) and [Re(MeDpe(+))(CO)(3)(bpy)](2+) (MeDpe(+)=N-methyl-4-[trans-2-(4-pyridyl)ethenyl]pyridinium, bpy=2,2'-bipyridine) were synthesized, characterized, and their redox and photonic properties were investigated by cyclic voltammetry; ultraviolet-visible-infrared (UV/Vis/IR) spectroelectrochemistry, stationary UV/Vis and resonance Raman spectroscopy; photolysis; picosecond time-resolved absorption spectroscopy in the visible and infrared regions; and time-resolved resonance Raman spectroscopy. The first reduction step of either complex occurs at about -1.1 V versus Fc/Fc(+) and is localized at MeDpe(+). Reduction alone does not induce a trans-->cis isomerization of MeDpe(+). [Re(Cl)(CO)(3)(MeDpe(+))(2)](2+) is photostable, while [Re(MeDpe(+))(CO)(3)(bpy)](2+) and free MeDpe(+) isomerize under near-UV irradiation. The lowest excited state of [Re(Cl)(CO)(3)(MeDpe(+))(2)](2+) has been identified as the Re(Cl)(CO)(3)-->MeDpe(+ 3)MLCT (MLCT=metal-to-ligand charge transfer), decaying directly to the ground state with lifetimes of approximately 42 (73 %) and approximately 430 ps (27 %). Optical excitation of [Re(MeDpe(+))(CO)(3)(bpy)](2+) leads to population of Re(CO)(3)-->MeDpe(+) and Re(CO)(3)-->bpy (3)MLCT states, from which a MeDpe(+) localized intraligand (3)pipi* excited state ((3)IL) is populated with lifetimes of approximately 0.6 and approximately 10 ps, respectively. The (3)IL state undergoes a approximately 21 ps internal rotation, which eventually produces the cis isomer on a much longer timescale. The different excited-state behavior of the two complexes and the absence of thermodynamically favorable interligand electron transfer in excited [Re(MeDpe(+))(CO)(3)(bpy)](2+) reflect the fine energetic balance between excited states of different orbital origin, which can be tuned by subtle structural variations. The complex [Re(MeDpe(+))(CO)(3)(bpy)](2+) emerges as a prototypical, multifunctional species with complementary redox and photonic behavior.

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“…For example, the complex [(bpy) 2 Ru(bp_vphv_bp)Ru(bpy) 2 ] is effectively an energy donor-acceptor system involving two Ru(II) diimine complex donors and a ligand localized acceptor. (Shaw et al 1990;Shaw and Schmehl 1991) The lowest energy excited state of bp_vphv_bp bridge is a 3 (p-p*) state with an energy (approx. 14,500 cm )1 ) significantly lower than that of the 3 MLCT state (approx.…”

Section: Influence Of Ligand Localized Excited States On Excited Statmentioning

confidence: 99%

The influence of bridging ligand electronic structure on the photophysical properties of noble metal diimine and triimine light harvesting systems

Wang

Guerzo

Baitalik³

et al. 2006

Photosynth Res

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This manuscript discusses the photophysical behavior of transition metal complexes of Ru(II) and Os(II) employed in development of light harvesting arrays of chromophores. Particular emphasis is placed on the relationship between the photophysical behavior of complexes having metal-to-ligand charge transfer (MLCT) excited states and the electronic characteristics of bridging ligands used in preparing oligometallic complexes. Examples are presented that discuss intramolecular energy migration in complexes having two distinct MLCT chromophores with bridging ligands that only very weakly couple the two chromophores. In addition, systems having bridging ligands with localized triplet excited states lower in energy than the MLCT state of the metal center to which they are attached are discussed. These systems very often have excited states localized on the bridging ligand with excited state lifetimes on the order of tens of microseconds. Finally, systems having Fe(II) metal centers, with very low energy MLCT states, are discussed. In complexes also containing bridging ligands with low energy triplet states, energy partitioning between the Fe center MLCT state (or Fe localized ligand field states) and the ligand triplet state is observed; the two states relax to the ground state via parallel pathways, but the Fe(II) center does not serve as an absolute excitation energy sink.

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Intersystem crossing to both ligand-localized and charge-transfer excited states in mononuclear and dinuclear ruthenium(II) diimine complexes

Cited by 101 publications

References 1 publication

Electron Delocalization in Ruthenium(II) and Osmium(II) 2,2‘-Bipyridyl Complexes Formed from Ethynyl-Bridged Ditopic Ligands

Electron Delocalization in Ruthenium(II) and Osmium(II) 2,2‘-Bipyridyl Complexes Formed from Ethynyl-Bridged Ditopic Ligands

Ultrafast Excited State Dynamics Controlling Photochemical Isomerization of N‐Methyl‐4‐[trans‐2‐(4‐pyridyl)ethenyl]pyridinium Coordinated to a {Re^I(CO)₃(2,2′‐bipyridine)} Chromophore

The influence of bridging ligand electronic structure on the photophysical properties of noble metal diimine and triimine light harvesting systems

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Intersystem crossing to both ligand-localized and charge-transfer excited states in mononuclear and dinuclear ruthenium(II) diimine complexes

Cited by 101 publications

References 1 publication

Electron Delocalization in Ruthenium(II) and Osmium(II) 2,2‘-Bipyridyl Complexes Formed from Ethynyl-Bridged Ditopic Ligands

Electron Delocalization in Ruthenium(II) and Osmium(II) 2,2‘-Bipyridyl Complexes Formed from Ethynyl-Bridged Ditopic Ligands

Ultrafast Excited State Dynamics Controlling Photochemical Isomerization of N‐Methyl‐4‐[trans‐2‐(4‐pyridyl)ethenyl]pyridinium Coordinated to a {ReI(CO)3(2,2′‐bipyridine)} Chromophore

The influence of bridging ligand electronic structure on the photophysical properties of noble metal diimine and triimine light harvesting systems

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Ultrafast Excited State Dynamics Controlling Photochemical Isomerization of N‐Methyl‐4‐[trans‐2‐(4‐pyridyl)ethenyl]pyridinium Coordinated to a {Re^I(CO)₃(2,2′‐bipyridine)} Chromophore