Photosubstitution in tris chelate complexes of ruthenium(II) containing the ligands 2,2'-bipyrazine, 2,2'-bipyrimidine, 2,2'-bipyridine, and 4,4'-dimethyl-2,2'-bipyridine: energy gap control

Ross, Haymo; Boldaji, M.; Rillema, D. Paul; Blanton, C.B.; White, Ross P.

doi:10.1021/ic00305a007

Cited by 96 publications

(67 citation statements)

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“…For [Ru(bpy) 2 (py) 2 ] 2+ , the photoinduced ligand exchange of one py ligand with Cl – in CH 3 CN was reported to take place with Φ 436 = 0.0059, and the introduction of −CH 3 groups to produce [Ru(4,4′-Me 2 bpy) 2 (py) 2 ] 2+ (4,4′-Me 2 bpy = 4,4′-dimethyl-2,2′-bipyridine) resulted in Φ 436 = 0.025 under similar experimental conditions. 49 The 4.2-fold increase in ligand exchange quantum yield is primarily a result of electronic effects from the electron-donating −CH 3 substituents. An electronic effect from the −CH 3 groups in 2 is expected, but the significantly larger Φ enhancement for 2 relative to 1 measured in the present work (>1600-fold; Table 1) indicates that the steric effects of the bulky NN ligand influence the photoreactivity to a much greater extent than electronic effects alone.…”

Section: Resultsmentioning

confidence: 99%

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Unusually Efficient Pyridine Photodissociation from Ru(II) Complexes with Sterically Bulky Bidentate Ancillary Ligands

et al. 2014

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The introduction of steric bulk to the bidentate ligand in [Ru(tpy)(bpy)(py)]2+ (1; tpy = 2,2′:2′,6″-terpyridine; bpy = 2,2′-bipyridine; py = pyridine) to provide [Ru(tpy)(Me2bpy)(py)]2+ (2; Me2bpy = 6,6′-dimethyl-2,2′-bipyridine) and [Ru(tpy)(biq)(py)]2+ (3; biq = 2,2′-biquinoline) facilitates photoinduced dissociation of pyridine with visible light. Upon irradiation of 2 and 3 in CH3CN (λirr = 500 nm), ligand exchange occurs to produce the corresponding [Ru(tpy)(NN)(NCCH3)]2+ (NN = Me2bpy, biq) complex with quantum yields, Φ500, of 0.16(1) and 0.033(1) for 2 and 3, respectively. These values represent an increase in efficiency of the reaction by 2–3 orders of magnitude as compared to that of 1, Φ500 < 0.0001, under similar experimental conditions. The photolysis of 2 and 3 in H2O with low energy light to produce [Ru(tpy)(NN)(OH2)]2+ (NN = Me2bpy, biq) also proceeds rapidly (λirr > 590 nm). Complexes 1–3 are stable in the dark in both CH3CN and H2O under similar experimental conditions. X-ray crystal structures and theoretical calculations highlight significant distortion of the planes of the bidentate ligands in 2 and 3 relative to that of 1. The crystallographic dihedral angles defined by the bidentate ligand, Me2bpy in 2 and biq in 3, and the tpy ligand were determined to be 67.87° and 61.89°, respectively, whereas only a small distortion from the octahedral geometry is observed between bpy and tpy in 1, 83.34°. The steric bulk afforded by Me2bpy and biq also result in major distortions of the pyridine ligand in 2 and 3, respectively, relative to 1, which are believed to weaken its σ-bonding and π-back-bonding to the metal and play a crucial role in the efficiency of the photoinduced ligand exchange. The ability of 2 and 3 to undergo ligand exchange with λirr > 590 nm makes them potential candidates to build photochemotherapeutic agents for the delivery of drugs with pyridine binding groups.

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Section: Resultsmentioning

confidence: 99%

“…Moreover, the efficiency of the reaction measured for 2 is ∼4-fold greater than the Cl – ligand exchange reported for [Ru(tpy)(py) 3 ] 2+ and cis -[Ru(tpy)(py) 2 Cl] + (λ irr = 436 nm). 49,50 …”

Section: Resultsmentioning

confidence: 99%

Unusually Efficient Pyridine Photodissociation from Ru(II) Complexes with Sterically Bulky Bidentate Ancillary Ligands

et al. 2014

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“…The latter condition should hold provided that the energy of the 3 LF states are not so low that intersystem crossing back to the ground state becomes too rapid and competes with ligand dissociation in accordance with the energy gap law. 44,50 …”

Section: Introductionmentioning

confidence: 99%

Unusual Role of Excited State Mixing in the Enhancement of Photoinduced Ligand Exchange in Ru(II) Complexes

Loftus

Fillman

et al. 2017

J. Am. Chem. Soc.

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Four Ru(II) complexes were prepared bearing two new tetradentate ligands, cyTPA and 1-isocyTPQA, which feature a piperidine ring that provides a structurally rigid backbone and facilitates the installation of other donors as the fourth chelating arm, while avoiding the formation of stereoisomers. The photophysical properties and photochemistry of [Ru(cyTPA)(CH3CN)2]2+ (1), [Ru(1-isocyTPQA)(CH3CN)2]2+ (2), [Ru(cyTPA)(py)2]2+ (3), and [Ru(1-isocyTPQA)-(py)2]2+ (4) were compared. The quantum yield for the CH3CN/H2O ligand exchange of 2 was measured to be Φ400 = 0.033(3), 5-fold greater than that of 1, Φ400 = 0.0066(3). The quantum yields for the py/H2O ligand exchange of 3 and 4 were lower, 0.0012(1) and 0.0013(1), respectively. DFT and related calculations show the presence of a highly mixed 3MLCT/3ππ* excited state as the lowest triplet state in 2, whereas the lowest energy triplet states in 1, 3, and 4 were calculated to be 3LF in nature. The mixed 3MLCT/3ππ* excited state places significant spin density on the quinoline moiety of the 1-isocyTPQA ligand positioned trans to the photolabile CH3CN ligand in 2, suggesting the presence of a trans-type influence in the excited state that enhances ligand exchange. Ultrafast spectroscopy was used to probe the excited states of 1–4, which confirmed that the mixed 3MLCT/3ππ* excited state in 2 promotes ligand dissociation, representing a new manner to effect photoinduced ligand exchange. The findings from this work can be used to design improved complexes for applications that require efficient ligand dissociation, as well as for those that require minimal deactivation of the 3MLCT state through low-lying metal-centered states.

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“…Photoinduced ligand dissociation speaks for the prominent contribution of the ligand field. Although usually neglected, however, Ru(II)-polypyridyl complexes suffer slight photodecomposition when potentially coordinating counter-anions are present in solution [91][92][93][94]. This detrimental ligand dissociation [95] is ascribed to thermal population of the upper lying T 2 level (MC) from T 1 [54]; this is the reason why osmium-based analogues, featuring a ca.…”

Section: Coarse-and Fine-tuning Of Excited-state Properties Of Ru(ii)mentioning

confidence: 99%

Conformationally gated photoinduced processes within photosensitizer–acceptor dyads based on ruthenium(II) and osmium(II) polypyridyl complexes with an appended pyridinium group

Lainé

Campagna

Loiseau

2008

Coordination Chemistry Reviews

104

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Photosubstitution in tris chelate complexes of ruthenium(II) containing the ligands 2,2'-bipyrazine, 2,2'-bipyrimidine, 2,2'-bipyridine, and 4,4'-dimethyl-2,2'-bipyridine: energy gap control

Cited by 96 publications

References 1 publication

Unusually Efficient Pyridine Photodissociation from Ru(II) Complexes with Sterically Bulky Bidentate Ancillary Ligands

Unusually Efficient Pyridine Photodissociation from Ru(II) Complexes with Sterically Bulky Bidentate Ancillary Ligands

Unusual Role of Excited State Mixing in the Enhancement of Photoinduced Ligand Exchange in Ru(II) Complexes

Conformationally gated photoinduced processes within photosensitizer–acceptor dyads based on ruthenium(II) and osmium(II) polypyridyl complexes with an appended pyridinium group

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