Expanding the Coordination Cage: A Ruthenium(II)−Polypyridine Complex Exhibiting High Quantum Yields under Ambient Conditions

Schramm, Frank; Meded, Velimir; Fliegl, Heike; Fink, Karin; Fuhr, Olaf; Qu, Zhi‐Rong; Klopper, Wim; Finn, S.; Keyes, Tia E.; Rüben, Mario

doi:10.1021/ic802040v

Cited by 73 publications

(87 citation statements)

References 112 publications

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“…43 The emissive excited state of Ir III complexes is a linear combination of a mixed 3 MLCT/ 3 LL′CT state (LL′CT = Scheme 1. Bis(tridentate)ruthenium(II) and Iridium(III) Polypyridine Complexes a a By Constable (A 2+ ), 15 van Koten (B 2+ , I + , J + , K + ), 20 Heinze (C 2+ , D 2+ , E 2+ ), 21−23 Hammarstrom (F 2+ ), 24 Ruben (G 2+ ), 25 Williams (H 2+ ), 26 and from this work (1 + and 2 + ).…”

Section: ■ Introductionmentioning

confidence: 99%

Understanding the Excited State Behavior of Cyclometalated Bis(tridentate)ruthenium(II) Complexes: A Combined Experimental and Theoretical Study

et al. 2015

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The synthesis and characterization of the donor-acceptor substituted cyclometalated ruthenium(II) polypyridine complex isomers [Ru(dpb-NHCOMe)(tpy-COOEt)](PF6) 1(PF6) and [Ru(dpb-COOEt)(tpy-NHCOMe)](PF6) 2(PF6) (dpbH = 1,3-dipyridin-2-ylbenzene, tpy = 2,2';6,2"-terpyridine) with inverted functional group pattern are described. A combination of resonance Raman spectroscopic and computational techniques shows that all intense visible range absorption bands arise from mixed Ru → tpy/Ru → dpb metal-to-ligand charge transfer (MLCT) excitations. 2(PF6) is weakly phosphorescent at room temperature in fluid solution and strongly emissive at 77 K in solid butyronitrile matrix, which is typical for ruthenium(II) polypyridine complexes. Density functional theory calculations revealed that the weak emission of 2(PF6) arises from a (3)MLCT state that is efficiently thermally depopulated via metal-centered ((3)MC) excited states. The activation barrier for the deactivation process was estimated experimentally from variable-temperature emission spectroscopic measurements as 11 kJ mol(-1). In contrast, 1(PF6) is nonemissive at room temperature in fluid solution and at 77 K in solid butyronitrile matrix. Examination of the electronic excited states of 1(PF6) revealed a ligand-to-ligand charge-transfer ((3)LL'CT) as lowest-energy triplet state due to the very strong push-pull effect across the metal center. Because of the orthogonality of the participating ligands, emission from the (3)LL'CT is symmetry-forbidden. Hence, in this type of complex a stronger push-pull effect does not increase the phosphorescence quantum yields but completely quenches the emission.

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Section: ■ Introductionmentioning

confidence: 99%

Understanding the Excited State Behavior of Cyclometalated Bis(tridentate)ruthenium(II) Complexes: A Combined Experimental and Theoretical Study

et al. 2015

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“…In addition, homoleptic meridional bis-tridentate complexes incorporated are Ru(TPy) 2 , 41 Ru(PzPyPz) 2 (PzPyPz = 2,6-di(pyrazol-1-yl)pyridine, sometimes called bpp), 42 Ru(DBPzP) 2 (DBPzP = 2,6-dibenzopyrazolyl-pyridine), 43 Ru(DQP) 2 , 23 and its 4-substituted analogs Ru(DQPCOOH) 2 , 44 Ru(DQPFur) 2 , and Ru(DQPNH 2 ) 2 . 44 These are combined with other expanded cage compounds that employ both saturated, Ru(PzbPybPz) 2 (PzbPybPz = 2,6-di(pyrazol-1-ylmethyl)pyridine) 45 and Ru(DCpP) 2 (DCpP = 6- bis (2-carboxypyridyl)pyridine), 46 and aromatic, Ru(DNinP) 2 (DQinP = 2,6-di(N-7-azaindol-1-yl)pyridine), 26 extensions between the central and terminal rings. In addition, the strain in ligands can be reduced by reducing some of the aromatic rings from six-membered rings to five like in Ru(DQxP) 2 (DQxP = 2,6-di(quinoxalin-5-yl)pyridine), 26 Ru(DQPz) 2 (DQPz = 1,3- bis (8-quinolinyl)-pyrazole), 47 and in Ru(DQPl) 2 (DQPl = 1,3- bis (8-quinolinyl)-pyrrole).…”

Section: Methodsmentioning

confidence: 99%

Predicting Structures of Ru-Centered Dyes: A Computational Screening Tool

Fredin

Allison

2016

J. Phys. Chem. A

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Dye-sensitized solar cells (DSCs) represent a means for harvesting solar energy to produce electrical power. Though a number of light harvesting dyes are in use, the search continues for more efficient and effective compounds to make commercially viable DSCs a reality. Computational methods have been increasingly applied to understand the dyes currently in use and to aid in the search for improved light harvesting compounds. Semiempirical quantum chemistry methods have a well-deserved reputation for giving good quality results in a very short amount of computer time. The most recent semiempirical models such as PM6 and PM7 are parameterized for a wide variety of molecule types, including organometallic complexes similar to DSC chromophores. In this article, the performance of PM6 is tested against a set of 20 molecules whose geometries were optimized using a density functional theory (DFT) method. It is found that PM6 gives geometries that are in good agreement with the optimized DFT structures. In order to reduce the differences between geometries optimized using PM6 and geometries optimized using DFT, the PM6 basis set parameters have been optimized for a subset of the molecules. It is found that it is sufficient to optimize the basis set for Ru alone to improve the agreement between the PM6 results and the DFT results. When this optimized Ru basis set is used, the mean unsigned error in Ru-ligand bond lengths is reduced from 0.043 Å to 0.017 Å in the set of 20 test molecules. Though the magnitude of these differences is small, the effect on the calculated UV/Vis spectra is significant. These results clearly demonstrate the value of using PM6 to screen DSC chromophores as well as the value of optimizing PM6 basis set parameters for a specific set of molecules.

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“…It enables a finetuning of their emissive properties by manipulation of the 3 MLCT energies via introduction of functional groups or extension of the aromatic backbone of the pyridine ligands. 75,[92][93][94][95][96] This allowed the design of specifically tailored complexes for luminescent sensing applications 97,98 and for optoelectronics. [99][100][101][102] The concept was successfully transferred to polypyridine complexes of other transition metals.…”

Section: Introductionmentioning

confidence: 99%

Excited state decay of cyclometalated polypyridine ruthenium complexes: insight from theory and experiment

Kreitner

Heinze

2016

Dalton Trans.

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Deactivation pathways of the triplet metal-to-ligand charge transfer ((3)MLCT) excited state of cyclometalated polypyridine ruthenium complexes with [RuN5C](+) coordination are discussed on the basis of the available experimental data and a series of density functional theory calculations. Three different complex classes are considered, namely with [Ru(N^N)2(N^C)](+), [Ru(N^N^N)(N^C^N)](+) and [Ru(N^N^N)(N^N^C)](+) coordination modes. Excited state deactivation in these complex types proceeds via five distinct decay channels. Vibronic coupling of the (3)MLCT state to high-energy oscillators of the singlet ground state ((1)GS) allows tunneling to the ground state followed by vibrational relaxation (path A). A ligand field excited state ((3)MC) is thermally accessible via a (3)MLCT →(3)MC transition state with the (3)MC state being strongly coupled to the (1)GS surface via a low-energy minimum energy crossing point (path B). Furthermore, a (3)MLCT →(1)GS surface crossing point directly couples the triplet and singlet potential energy surfaces (path C). Charge transfer states either with higher singlet character or with different orbital parentage and intrinsic symmetry restrictions are thermally populated which promote non-radiative decay via tunneling to the (1)GS state (path D). Finally, the excited state can decay via phosphorescence (path E). The dominant deactivation pathways differ for the three individual complex classes. The implications of these findings for isoelectronic iridium(iii) or iron(ii) complexes are discussed. Ultimately, strategies for optimizing the emission efficiencies of cyclometalated polypyridine complexes of d(6)-metal ions, especially Ru(II), are suggested.

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Expanding the Coordination Cage: A Ruthenium(II)−Polypyridine Complex Exhibiting High Quantum Yields under Ambient Conditions

Cited by 73 publications

References 112 publications

Understanding the Excited State Behavior of Cyclometalated Bis(tridentate)ruthenium(II) Complexes: A Combined Experimental and Theoretical Study

Understanding the Excited State Behavior of Cyclometalated Bis(tridentate)ruthenium(II) Complexes: A Combined Experimental and Theoretical Study

Predicting Structures of Ru-Centered Dyes: A Computational Screening Tool

Excited state decay of cyclometalated polypyridine ruthenium complexes: insight from theory and experiment

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