Excited state investigation of a new Ru(<scp>ii</scp>) complex for dual reactivity with low energy light

Knoll, Jessica D.; Albani, Bryan A.; Turró, Claudia

doi:10.1039/c5cc01865j

Cited by 71 publications

(111 citation statements)

References 21 publications

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“…The ligand exchange efficiency for 2 is approximately an order of magnitude lower than the previously reported compounds, and the difference is attributed to the presence of a low-lying dppn 3 ππ* state which provides a competing pathway for excited state deactivation. This trend is also observed in Ru(II)-polypyridyl complexes containing dppn-type ligands [29,30]. The quantum yield for singlet oxygen production for 2 was determined to be 0.22(7), a value similar to the related Rh 2 (II,II)-dppn compounds cis -[Rh 2 (μ-O 2 CCH 3 ) 2 (dppn)(L)] 2+ (L = dppz, dppn) with Φ 1 O 2 = 0.40 [17].…”

Section: Resultssupporting

confidence: 56%

“…In addition, [Ru(bpy)(dppn)(CH 3 CN) 2 ] 2+ , produces 1 O 2 with high efficiency, Φ 460 = 0.72, and also exchanges a CH 3 CN ligand for a H 2 O solvent molecule, Φ 400 = 0.002(3) [29]. Similarly, Ru(II) compounds that exhibit dual photoreactivity have been reported; these complexes exchange pyridyl ligands for solvent molecules while also producing 1 O 2 and include [Ru(tpy)(Me 2 dppn)(py)] 2+ (Me 2 dppn = 3,6-dimethylbenzo[ i ]dipyrido[3,2- a :2′,3′- c ]phenazine) with Φ 1 O 2 = 0.69(9) in CH 3 OH and quantum yield for ligand exchange, Φ 500 , measured to be 0.053(1) in CH 3 CN [30]. Similarly, [Ru(pydppn)(biq)(py)] 2+ exhibits Φ 1 O 2 = 0.75(7) in CH 3 OH and Φ 500 = 0.0070(4) in CH 3 CN [31].…”

Section: Introductionmentioning

confidence: 99%

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Dual photoreactivity of a new Rh2(II,II) complex for biological applications

Akhimie

White

Turró

2017

Inorganica Chimica Acta

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A new Rh2(II,II) complex containing one dppn (benzo[i]dipyrido[3,2-a:2,3-c]phenazine) ligand with an extended π-system, cis-H,H-[Rh2(OCCH3NH)2(dppn)(CH3CN)2]2+ (2), was synthesized and characterized. The dppn ligand, which serves as a DNA base pair intercalator, chelates to a single Rh center and is positioned trans to the amidato N atoms of the bridging acetamide ligand. This ligand also possesses a low-lying dppn-centered 3ππ* state that is advantageous for the sensitization of singlet oxygen (1O2), which complex 2 produced with a quantum yield, Φ1O2 460, of 0.22(7) with 460 nm excitation. In addition, one equivalent of CH3CN is released from 2 upon irradiation with visible light, generating cis-H,H-[Rh2(OCCH3NH)2(dppn)(H2O)(CH3CN)]2+ in aqueous media with photoinduced ligand exchange quantum yield, ΦLE 450, of 0.0033(1). Thermal denaturation and relative viscosity studies are consistent with a π-stacking interaction of 2 with double-stranded DNA together with covalent binding to the duplex upon irradiation with visible light. Therefore, 2 exhibits dual photoreactivity towards DNA, making it potentially useful for photochemotherapy with enhanced activity relative to compounds able to achieve only one mode of cell death upon irradiation.

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Section: Resultssupporting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Dual photoreactivity of a new Rh2(II,II) complex for biological applications

Akhimie

White

Turró

2017

Inorganica Chimica Acta

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“…The Me 2 dppn ligand causes geometric strain similar to that caused by Me 2 bpy, but the complex maintains the Me 2 dppn 3 ππ * lowest-energy excited state. 48 [Ru(tpy)(Me 2 dppn)(py)] 2+ absorbs strongly in the visible region with dppn-centered 1 ππ * transitions at 382 nm (11 400 M −1 cm −1 ) and 404 nm (12 400 M −1 cm −1 ) and a 1 MLCT peak at 486 nm (12 900 M −1 cm −1 ). When photolyzed in CH 3 CN ( λ irr = 500 nm), [Ru(tpy)(Me 2 dppn)(CH 3 CN)] 2+ is formed with Φ 500 = 0.053(1) in the absence of O 2 , but ligand exchange is not observed in [Ru(tpy)(dppn)(py)] 2+ (Φ 500 < 10 −4 ), which lacks steric strain (Table 2).…”

Section: Dual Activity: Photoinduced Ligand Exchange and 1o2 Generationmentioning

confidence: 99%

New Ru(II) Complexes for Dual Photoreactivity: Ligand Exchange and ¹O₂ Generation

2015

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CONSPECTUS Uncovering the factors that govern the electronic structure of Ru(II)–polypyridyl complexes is critical in designing new compounds for desired photochemical reactions, and strategies to tune excited states for ligand dissociation and 1O2 production are discussed herein. The generally accepted mechanism for photoinduced ligand dissociation proposes that population of the dissociative triplet ligand field (3LF) state proceeds through thermal population from the vibrationally cooled triplet metal-to-ligand charge transfer (3MLCT) state; however, temperature-dependent emission spectroscopy provides varied activation energies using the emission and ligand exchange quantum yields for [Ru(bpy)2(L)2]2+ (bpy = 2,2′-bipyridine; L = CH3CN or py). This suggests that population of the 3LF state proceeds from the vibrationally excited 3MLCT state. Because the quantum yield of ligand dissociation for nitriles is much more efficient than that for py, steric bulk was introduced into the ligand set to distort the pseudo-octahedral geometry and lower the energy of the 3LF state. The py dissociation quantum yield with 500 nm irradiation in a series of [Ru(tpy)(NN)(py)]2+ complexes (tpy = 2,2′:6′,2″-terpyridine; NN = bpy, 6,6′-dimethyl-2,2′-bipyridine (Me2bpy), 2,2′-biquinoline (biq)) increases by 2–3 orders of magnitude with the sterically bulky Me2bpy and biq ligands relative to bpy. Ultrafast transient absorption spectroscopy reveals population of the 3LF state within 3–7 ps when NN is bulky, and density functional theory calculations support stabilized 3LF states. Dual activity via ligand dissociation and 1O2 production can be achieved by careful selection of the ligand set to tune the excited-state dynamics. Incorporation of an extended π system in Ru(II) complexes such as [Ru(bpy)(dppn)(CH3CN)2]2+ (dppn = benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine) and [Ru(tpy)(Me2dppn)(py)]2+ (Me2dppn = 3,6-dimethylbenzo[i]dipyrido[3,2-a:2′,3′-c]phenazine) introduces low-lying, long-lived dppn/Me2dppn 3ππ* excited states that generate 1O2. Similar to [Ru(bpy)2(CH3CN)2]2+, photodissociation of CH3CN occurs upon irradiation of [Ru(bpy)(dppn)(CH3CN)2]2+, although with lower efficiency because of the presence of the 3ππ* state. The steric bulk in [Ru(tpy)(Me2dppn)(py)]2+ is critical in facilitating the photoinduced py dissociation, as the analogous complex [Ru(tpy)(dppn)(py)]2+ produces 1O2 with near-unit efficiency. The ability to tune the relative energies of the excited states provides a means to design potentially more active drugs for photochemotherapy because the photorelease of drugs can be coupled to the therapeutic action of reactive oxygen species, effecting cell death via two different mechanisms. The lessons learned about tuning of the excited-state properties can be applied to the use of Ru(II)–polypyridyl compounds in a variety of applications, such as solar energy conversion, sensors and switches, and molecular machines.

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“…[Ru(tpy)(bpy)(py)] 2+ and [Ru(tpy)(Me 2 bpy)(py)] 2+ complexes (Scheme 1) are stable in the dark, and the latter releases pyridine efficiently upon irradiation with visible light, whereas pyridine ligand exchange is not observed in the former upon photoexcitation under the same conditions. 25 …”

Section: Introductionmentioning

confidence: 99%

“…25–37 Through steric crowding about the Ru center, the Ru–N 5 and Ru–N 6 bonds are distorted in [Ru(tpy)(Me 2 bpy)(py)] 2+ relative to [Ru(tpy)-(bpy)(py)] 2+ . As a result, the energy difference between the 3 MC and 3 MLCT states is smaller in Ru(tpy)(Me 2 bpy)(py)] 2+ , allowing for efficient population of the 3 MC state and increase Higher resolution plots of the biorthogonal and canonical SOMOs are available in Figure S1 and S2 of the Supporting Information.…”

Section: Introductionmentioning

confidence: 99%

DFT Investigation of Ligand Photodissociation in [Ru^II(tpy)(bpy)(py)]²⁺ and [Ru^II(tpy)(Me₂bpy)(py)]²⁺ Complexes

Nisbett

Turró

et al. 2017

Inorg. Chem.

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Photoinduced ligand dissociation of pyridine occurs much more readily in [Ru(tpy)(Me2bpy)(py)]2+ than in [Ru(tpy)(bpy)(py)]2+ (tpy = 2,2′:6′,2″-terpyridine; bpy = 2,2′-bipyridine, Me2bpy = 6,6′-dimethyl-2,2′-bipyridine; py = pyridine). The S0 ground state and the 3MLCT and 3MC excited states of these complexes have been studied using BP86 density functional theory with the SDD basis set and effective core potential on Ru and the 6–31G(d) basis set for the rest of the atoms. In both complexes, excitation by visible light and intersystem crossing leads to a 3MLCT state in which an electron from a Ru d orbital has been promoted to a π* orbital of terpyridine, followed by pyridine release after internal conversion to a dissociative 3MC state. Interaction between the methyl groups and the other ligands causes significantly more strain in [Ru(tpy)(Me2bpy)(py)]2+ than in [Ru(tpy)(bpy)(py)]2+, in both the S0 and 3MLCT states. Transition to the dissociative 3MC states releases this strain, resulting in lower barriers for ligand dissociation from [Ru(tpy)(Me2bpy)(py)]2+ than from [Ru(tpy)(bpy)(py)]2+. Analysis of the molecular orbitals along relaxed scans for stretching the Ru–N bonds reveals that ligand photodissociation is promoted by orbital mixing between the ligand π* orbital of tpy in the 3MLCT state and the dσ* orbitals that characterize the dissociative 3MC states. Good overlap and strong mixing occur when the Ru–N bond of the leaving ligand is perpendicular to the π* orbital of terpyridine, favoring the release of pyridine positioned in a cis fashion to the terpyridine ligand.

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Excited state investigation of a new Ru(ii) complex for dual reactivity with low energy light

Cited by 71 publications

References 21 publications

Dual photoreactivity of a new Rh2(II,II) complex for biological applications

Dual photoreactivity of a new Rh2(II,II) complex for biological applications

New Ru(II) Complexes for Dual Photoreactivity: Ligand Exchange and ¹O₂ Generation

DFT Investigation of Ligand Photodissociation in [Ru^II(tpy)(bpy)(py)]²⁺ and [Ru^II(tpy)(Me₂bpy)(py)]²⁺ Complexes

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Excited state investigation of a new Ru(ii) complex for dual reactivity with low energy light

Cited by 71 publications

References 21 publications

Dual photoreactivity of a new Rh2(II,II) complex for biological applications

Dual photoreactivity of a new Rh2(II,II) complex for biological applications

New Ru(II) Complexes for Dual Photoreactivity: Ligand Exchange and 1O2 Generation

DFT Investigation of Ligand Photodissociation in [RuII(tpy)(bpy)(py)]2+ and [RuII(tpy)(Me2bpy)(py)]2+ Complexes

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New Ru(II) Complexes for Dual Photoreactivity: Ligand Exchange and ¹O₂ Generation

DFT Investigation of Ligand Photodissociation in [Ru^II(tpy)(bpy)(py)]²⁺ and [Ru^II(tpy)(Me₂bpy)(py)]²⁺ Complexes