Thermal and Photoinduced Electron Transfer in Directional Bis(terpyridine)ruthenium(II)–(Bipyridine)platinum(II) Complexes

Dietrich, Jan; Leupoldt, Anica Wünsche von; Grabolle, Markus; Resch‐Genger, Ute; Heinze, Katja

doi:10.1002/ejic.201201531

Cited by 16 publications

(24 citation statements)

References 66 publications

(170 reference statements)

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“…Spectral changes of similar shape have been observed previously with dinuclear amide conjugates in our group upon addition of decamethylcobaltocene as reductant. 39,40 The results obtained in the current study suggest that also in those cases the bridging amide is deprotonated in the presence of H 2 O (UV−vis) after initial reduction of the complexes (rapid-freeze EPR). The same process, namely, deprotonation of 3 4+ , is observed when monitoring the addition of CoCp* 2 via NMR spectroscopy (slow time scale).…”

Section: Inorganic Chemistrymentioning

confidence: 70%

Dual Emission and Excited-State Mixed-Valence in a Quasi-Symmetric Dinuclear Ru–Ru Complex

et al. 2014

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The synthesis and characterization of the new dinuclear dipeptide [(EtOOC-tpy)Ru(tpy-NHCO-tpy)Ru(tpy-NHCOCH3)](4+) 3(4+) of the bis(terpyridine)ruthenium amino acid [(HOOC-tpy)Ru(tpy-NH2)](2+) 1(2+) are described, and the properties of the dipeptide are compared to those of the mononuclear complex [(EtOOC-tpy)Ru(tpy-NHCOCH3)](2+) 4(2+) carrying the same functional groups. 3(4+) is designed to serve a high electronic similarity of the two ruthenium sites despite the intrinsic asymmetry arising from the amide bridge. This is confirmed via UV-vis absorption and NMR spectroscopy as well as cyclic voltammetry. 4(2+) and 3(4+) are emissive at room temperature, as expected. Moreover, 3(4+) exhibits dual emission from two different triplet states with different energies and lifetimes at room temperature. This is ascribed to the presence of a unique thermal equilibrium between coexisting [Ru(II)(tpy-NHCO-tpy(·-))Ru(III)] and [Ru(III)(tpy-NHCO-tpy(·-))Ru(II)] states leading to an unprecedented excited-state Ru(II)Ru(III) mixed-valent system via the radical anion bridge tpy-NHCO-tpy(·-). The mixed-valent cation 3(5+), on the other hand, shows no measurable interaction of the Ru(II)Ru(III) centers via the neutral bridge tpy-NHCO-tpy (Robin-Day class I). Reduction of 3(4+) to the radical cation 3(3+) by decamethylcobaltocene is bridge-centered as evidenced by rapid-freeze electron paramagnetic resonance spectroscopy. Interestingly, all attempts to observe 3(3+) via NMR and UV-vis absorption spectroscopy only led to the detection of the diamagnetic complex 3-H(3+) in which the bridging amide is deprotonated. Hence 3-H(3+) (and 4-H(+)) appear to reduce protons to dihydrogen. The ease of single and double deprotonation of 4(2+) and 3(4+) to 4-H(+), 3-H(3+), and 3-2H(2+) was demonstrated using a strong base and was studied using NMR and UV-vis absorption spectroscopies. The equilibrating excited triplet states of 3(4+) are reductively quenched by N,N-dimethylaniline assisted by hydrogen bonding to the bridging amide.

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Section: Inorganic Chemistrymentioning

confidence: 70%

Dual Emission and Excited-State Mixed-Valence in a Quasi-Symmetric Dinuclear Ru–Ru Complex

et al. 2014

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“…This is an important finding, as Re(bpy)(L) 3 X complexes and chromophore-appended derivatives, for example [56] 3+ in Figure 20, have been reported to photocatalytically reduce CO 2 to CO via [Re(bpy)] · active sites. [78] In addition to the expected tpy-CO reductions at E 1/2 = -1.47 and -1.45 V and Ru II /Ru III oxidation waves at E 1/2 = +0. Heterometallic Ru/M reference compounds (M = Re, Pt).…”

Section: Mixed-valence and Mixed-metal Complexesmentioning

confidence: 87%

“…Then, even comparably mild coupling conditions, for example PfpOH/DCC, are sufficient to overcome the Coulomb repulsion between two positively charged complex fragments to yield dinuclear quadruply charged species (see below). [18,25,61,77,78] Amino acid [5] 2+ ( Figure 2) has even been employed as building block in solid-phase peptide synthesis (SPPS) by our group. [18,25,61,77,78] Amino acid [5] 2+ ( Figure 2) has even been employed as building block in solid-phase peptide synthesis (SPPS) by our group.…”

Section: Amide Bond Formation and Solid-phase Peptide Synthesismentioning

confidence: 99%

“…Electrochemical studies reveal a reversible Ru II /Ru III redox process at E 1/2 = 0.68 V for amines [50] [77,78] The optical and redox data of bpy derivatives [49] 2+ - [52] 2+ suggest that these complexes can be considered as chromophore-and redox-switch-functionalized metallo ligands. Hence, typical bpy coordination chemistry is possible with these phosphorescent, redox-active metallo ligands.…”

Section: Mixed-valence and Mixed-metal Complexesmentioning

confidence: 99%

“…[77] While the first oxidation of [53] 3 Cl/[Re(bpy)(CO) 3 Cl]redox couple resulting density from the bridging bpy-CO to the terminal tpy-CO ligand both in radical [53] + and in the triplet excited state of [53] 2+ . [78] Upon coordination of the PtCl 2 fragment, new absorption bands appear at λ max = 408 nm ([57] 2+ ) and at λ max = 364 nm ([58] 2+ ), assigned to platinum to bpy-CO and platinum to bpy-NH MLCT bands [ 1 MLCT(Pt/bpy)], respectively. [125,126] Figure 20.…”

Section: Mixed-valence and Mixed-metal Complexesmentioning

confidence: 99%

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Redox and Photochemistry of Bis(terpyridine)ruthenium(II) Amino Acids and Their Amide Conjugates – from Understanding to Applications

2014

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The push-pull-substituted bis(terpyridine)ruthenium(II) amino acid [Ru(4Ј-tpy-COOH)(4Ј-tpy-NH 2 )] 2+ ([5] 2+ ; tpy = 2,2Ј;6Ј,2ЈЈ-terpyridine) with carboxylic acid and amino substituents features exceptional chemical and photophysical properties. Its interaction with photons, electrons, and/or protons results in room-temperature phosphorescence, reversible oxidative and reductive redox chemistry, reversible acid/ base chemistry, proton-coupled electron transfer, photoinduced reductive and oxidative electron transfer, excited-state proton transfer and energy transfer reactions. These properties can be fine-tuned by variations of the bis(terpyridine) amino acid motif, namely extension of the π system and ex-[a] Institute www.eurjic.org MICROREVIEW curs. [1] The long excited-state lifetime (τ ≈ 1 μs) of the 3 MLCT state at room temperature in solution renders [Ru(bpy) 3 ] 2+ exceptionally suitable as a photoredox catalyst (Table 1). [38,45,46] The 3 MLCT state is emissive with a high phosphorescence quantum yield (Φ ≈ 10 %), which favors applications in light-emitting devices as luminescent sensors or as imaging agents. [46] The properties of [Ru(bpy) 3 ] 2+ can easily be tailored by modifications of the bpy ligand. However, the intrinsic Δ, Λ chirality of [Ru(bpy) 3 ] 2+ is a serious drawback when more than one bpy ligand is substituted or when more than one [Ru(bpy) 3 ] 2+ -type complexes are combined to form di-or oligonuclear complexes, because diastereomeric complexes (e.g. rac-Δ,Δ/Λ,Λ and meso-Δ,Λ) have to be separated or avoided by complicated synthetic procedures. [47][48][49] It is obvious that interaction with chiral molecules, such as DNA or proteins, will even modify the individual properties of Δ, Λ enantiomers, and any interaction with chiral biomolecules is complicated when using racemates, for example as anticancer drugs. [48d] Bis(tridentate) meridional coordination as in [Ru(tpy) 2 ] 2+ ([1] 2+ , Figure 2) avoids the formation of diastereomers even in the case of heteroleptic [Ru(tpy-R 1 )(tpy-R 2 )] 2+[50] and dinuclear complexes (tpy-R 1 , tpy-R 2 = 4Ј-substituted 2,2Ј;6Ј,2ЈЈ-terpyridine). [25,51,52] Furthermore, the stronger Aaron Breivogel received his diploma in chemistry at the Johannes Gutenberg University of Mainz, Germany, in 2009, and he is currently finishing his Ph.D. Thesis in the research group of Prof. Dr. Katja Heinze in inorganic chemistry. During his studies he spent one semester (2007/2008) at the University of Valencia, Spain, in the Department of Analytical Chemistry in the group of Prof. Dr. Miguel de la Guardia working on the quantitative determination of glycolic acid in cosmetics by online liquid chromatography and Fourier transform infrared spectroscopy. Currently he is working on the synthesis of bis(tridentate) complexes of ruthenium(II) and their applications in dye-sensitized solar cells and lightemitting electrochemical cells. He received a grant from the "International Research Training Group (IRTG) 1404 -Self-organized Materials for Optoelectronics" funded by t...

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Excited State Tuning of Bis(tridentate) Ruthenium(II) Polypyridine Chromophores by Push–Pull Effects and Bite Angle Optimization: A Comprehensive Experimental and Theoretical Study

Breivogel

Meister

Förster

et al. 2013

Chemistry A European J

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The synergy of push-pull substitution and enlarged ligand bite angles has been used in functionalized heteroleptic bis(tridentate) polypyridine complexes of ruthenium(II) to shift the (1) MLCT absorption and the (3) MLCT emission to lower energy, enhance the emission quantum yield, and to prolong the (3) MLCT excited-state lifetime. In these complexes, that is, [Ru(ddpd)(EtOOC-tpy)][PF6 ]2 , [Ru(ddpd-NH2 )(EtOOC-tpy)][PF6 ]2 , [Ru(ddpd){(MeOOC)3 -tpy}][PF6 ]2 , and [Ru(ddpd-NH2 ){(EtOOC)3 -tpy}][PF6 ]2 the combination of the electron-accepting 2,2';6',2''-terpyridine (tpy) ligand equipped with one or three COOR substituents with the electron-donating N,N'-dimethyl-N,N'-dipyridin-2-ylpyridine-2,6-diamine (ddpd) ligand decorated with none or one NH2 group enforces spatially separated and orthogonal frontier orbitals with a small HOMO-LUMO gap resulting in low-energy (1) MLCT and (3) MLCT states. The extended bite angle of the ddpd ligand increases the ligand field splitting and pushes the deactivating (3) MC state to higher energy. The properties of the new isomerically pure mixed ligand complexes have been studied by using electrochemistry, UV/Vis absorption spectroscopy, static and time-resolved luminescence spectroscopy, and transient absorption spectroscopy. The experimental data were rationalized by using density functional calculations on differently charged species (charge n=0-4) and on triplet excited states ((3) MLCT and (3) MC) as well as by time-dependent density functional calculations (excited singlet states).

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Thermal and Photoinduced Electron Transfer in Directional Bis(terpyridine)ruthenium(II)–(Bipyridine)platinum(II) Complexes

Cited by 16 publications

References 66 publications

Dual Emission and Excited-State Mixed-Valence in a Quasi-Symmetric Dinuclear Ru–Ru Complex

Dual Emission and Excited-State Mixed-Valence in a Quasi-Symmetric Dinuclear Ru–Ru Complex

Redox and Photochemistry of Bis(terpyridine)ruthenium(II) Amino Acids and Their Amide Conjugates – from Understanding to Applications

Excited State Tuning of Bis(tridentate) Ruthenium(II) Polypyridine Chromophores by Push–Pull Effects and Bite Angle Optimization: A Comprehensive Experimental and Theoretical Study

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