Polypyridyl Sensitizers Research Articles

Correction to “Fundamental Factors Impacting the Stability of Phosphonate-Derivatized Ruthenium Polypyridyl Sensitizers Adsorbed on Metal Oxide Surfaces”

Correction to “Fundamental Factors Impacting the Stability of Phosphonate-Derivatized Ruthenium Polypyridyl Sensitizers Adsorbed on Metal Oxide Surfaces”

Fundamental Factors Impacting the Stability of Phosphonate-Derivatized Ruthenium Polypyridyl Sensitizers Adsorbed on Metal Oxide Surfaces.

A series of 18 ruthenium(II) polypyridyl complexes were synthesized and evaluated under electrochemically oxidative conditions, which generates the Ru(III) oxidation state and mimics the harsh conditions experienced during the kinetically limited regime that can occur in dye-sensitized solar cells (DSSCs) and dye-sensitized photo-electrosynthesis cells, to further develop fundamental insights into the factors governing molecular sensitizer surface stability in aqueous 0.1 M HClO4. Both desorption and oxidatively induced ligand substitution were observed on planar fluorine-doped tin oxide (FTO) electrodes, with a dependence on the E1/2 Ru(III/II) redox potential dictating the comparative ratios of the processes. Complexes such as RuP4OMe ( E1/2 = 0.91 vs Ag/AgCl) displayed virtually only desorption, while complexes such as RuPbpz ( E1/2 > 1.62 V vs Ag/AgCl) displayed only chemical decomposition. Comparing isomers of 4,4'- and 5,5'-disubstituted-2,2'-bipyridine ancillary ligands, a dramatic increase in the rate of desorption of the Ru(III) complexes was observed for the 5,5'-ligands. Nanoscopic indium-doped tin oxide thin films (nanoITO) were also sensitized and analyzed with cyclic voltammetry, UV-vis absorption spectroscopy, and X-ray photoelectron spectroscopy, allowing for further distinction of desorption versus ligand-substitution processes. Desorption loss to bulk solution associated with the planar surface of FTO is essentially non-existent on nanoITO, where both desorption and ligand substitution are shut down with RuP4OMe. These results revealed that minimizing time spent in the oxidized form, incorporating electron-donating groups, maximizing hydrophobicity, and minimizing molecular bulk near the adsorbed ligand are critical to optimizing the performance of ruthenium(II) polypyridyl complexes in dye-sensitized devices.

Theoretical study on spin-forbidden transitions of osmium complexes by two-component relativistic time-dependent density functional theory

We study spin-forbidden transitions of Os polypyridyl sensitizers by two-component relativistic time-dependent density functional theory with the spin–orbit interaction based on Tamm–Dancoff approximation. The absorption spectra, including spin-forbidden-transition peaks, for the Os complexes are reasonably reproduced in comparison with the experimental ones. The extension of the conjugated lengths in the Os complexes is investigated and found to be effective to enhance photo absorption for spin-allowed transitions as well as spin-forbidden ones. This study provides fruitful information for a design of new dyes in terms of conjugation lengths.

Two-component relativistic time-dependent density functional theory study on spin-forbidden transitions for metal polypyridyl complexes

Spin-forbidden transitions of metal polypyridyl sensitizers are studied by the two-component relativistic time-dependent density functional theory with spin–orbit interaction based on Tamm–Dancoff approximation. The spin-forbidden transitions for a phosphine-coordinated Ru(II), DX1, as well as the modified DX1 complexes whose Ru is replaced with Fe and Os, are calculated. The role of the central metals in spin-forbidden transitions is discussed toward the exploration for new efficient sensitizers.

Advances in high efficiency dye sensitized solar cells based on Ru(ii) free sensitizers and a liquid redox electrolyte

Dye sensitized solar cells (DSCs) are one of the most promising cost effective emerging technologies for clean energy generation using solar radiation. Though many of the highest efficiencies have been associated with Ru(II) polypyridyl sensitizers, Ru(II) free sensitizers have made great progress recently and are now serious alternatives. Indeed the highest efficiency recorded in the literature of 12.05% under standard 100 mW cm−2 illumination was obtained using Ru(II) free sensitizers. In this highlight, recent progress in DSCs based on sensitizers such as porphyrins, phthalocyanines, squarines, indolenes, perylenes and donor–(π bridge)–acceptor (D–π–A) dyes is discussed.

Amphiphilic Ruthenium(II) Terpyridine Sensitizers with Long Alkyl Chain Substituted β-Diketonato Ligands: An Efficient Coadsorbent-Free Dye-Sensitized Solar Cells

Three alkyl-substitutedβ-diketonato-ruthenium(II)-polypyridyl sensitizers with different alkyl chain lengths, [Ru(tctpy)(tfpd)(NCS)] (A1), [Ru(tctpy)(tfdd)(NCS)] (A2), and [Ru(tctpy)(tfid)(NCS)] (A3), were designed and synthesized for dye-sensitized solar cells (DSCs) to investigate the effect of bulky alkyl chain substituents on the photovoltaic performances (where tctpy = 4,4′,4′′-tricarboxy-2,2′:;6′,2′′-terpyridine, tfpd =1,1,1-trifluoropentane-2,4-dione, tfdd = 1,1,1-trifluorodecane-2,4-dione, and tfid =1,1,1-trifluoroicosane-2,4-dione). These complexes exhibit a broad metal-to-ligand charge transfer absorption band over the whole visible range extending up to 950 nm. All complexes were examined in the presence and absence of the coadsorbent deoxycholic acid (DCA) in dye-bath solutions. These sensitizers, when anchored to nanocrystalline TiO2films, achieve efficient sensitization to TiO2electrodes. Under standard AM 1.5 sunlight, the complexA3containing long alkyl chain length of C16yielded a short-circuit photocurrent density of 18.0 mA/cm2, an open-circuit voltage of 0.64 V, and a fill factor of 0.66, corresponding to an overall conversion efficiency of 7.6% in the absence of DCA. The power conversion efficiency ofA1sensitized DSCs was significantly increased upon the addition of DCA as compared to that in the absence of DCA. However, the photovoltaic performance ofA3was not dependent on DCA at all, probably due to the inherent structural nature of theA3molecule.

Synthesis and Application of New Ruthenium Complexes Containingβ-Diketonato Ligands as Sensitizers for Nanocrystalline TiO2Solar Cells

Five heteroleptic ruthenium complexes having differentβ-diketonato ligands, [Ru(tctpy)(dppd)(NCS)] (1), [Ru(tctpy)(pd)(NCS)] (2), [Ru(tctpy)(tdd)(NCS)] (3), [Ru(tctpy)(mepd)(NCS)] (4), and [Ru(tctpy)(tmhd)(NCS)] (5), where tctpy = 4,4′,4′′-tricarboxy-2,2′:6′,2′′-terpyridine, pd = pentane-2,4-dione, mepd = 3-methylpentane-2,4-dione, tmhd = 2,2,6,6-tetramethylheptane-3,5-dione, tdd = tridecane-6,8-dione, and dppd = 1,3-diphenylpropane-1,3-dione, were synthesized and characterized. These heteroleptic complexes exhibit a broad metal-to-ligand charge transfer absorption band over the whole visible range extending up to 950 nm. The low-energy absorption bands and theE (Ru3+/2+) oxidation potentials in these complexes could be tuned to about 15 nm and 110 mV, respectively, by choosing appropriateβ-diketonate ligands. Molecular orbital calculation of complex1shows that the HOMO is localized on the NCS ligand and the LUMO is localized on the tctpy ligand, which is anchored to the TiO2nanoparticles. Theβ-diketonato-ruthenium(II)-polypyridyl sensitizers, when anchored to nanocrystalline TiO2films for light to electrical energy conversion in regenerative photoelectrochemical cells, achieve efficient sensitization to TiO2electrodes with increasing activity in the order5<4<3≈2<1. Under standard AM 1.5 sunlight, the complex1yielded a short-circuit photocurrent density of 16.7 mA/cm2, an open-circuit voltage of 0.58 V, and a fill factor of 0.64, corresponding to an overall conversion efficiency of 6.2%. A systematic tuning of HOMO energy level shows that an efficient sensitizer should possess a ground-state redox potential value of >+.53 V versus SCE.

Direct Observation of Photodriven Intermolecular Hole Transfer across TiO2 Nanocrystallites: Lateral Self-Exchange Reactions and Catalyst Oxidation

Photoselection of Ru(II)-polypyridyl sensitizers with polarized pulsed-light excitation, when anchored to TiO(2) nanocrystallites interconnected in a mesoporous thin film, results in an anisotropic distribution of excited sensitizers. Under conditions where excited-state sensitizers efficiently inject electrons into TiO(2), the resulting oxidized sensitizers exhibit an initial anisotropy in their absorption difference spectra. Over the course of the charge-separated lifetime for many sensitizers, the transient absorption anisotropy signal decays to nearly zero indicative of lateral self-exchange hole-transfer reactions at the interface. When a cobalt metalloporphyrin catalyst was coanchored to the sensitized nanocrystalline TiO(2) film, excited-state injection was followed by lateral hole transfer to oxidize the surface-bound catalyst.

Synthesis and Characterization of New Efficient Tricarboxyterpyridyl (β-diketonato) Ruthenium(II) Sensitizers and Their Applications in Dye-Sensitized Solar Cells

A new series of aryl-substituted β-diketonato-ruthenium(II)-polypyridyl sensitizers, [Ru(Htctpy)(tfpbd)(NCS){(C4H9)4N}2] (1), [Ru(Htctpy)(tffpbd)(NCS){(C4H9)4N}2] (2), and [Ru(Htctpy)(tfcpbd)(NCS){(C4H9)4N}2] (3), were synthesized and fully characterized by elemental analysis, UV−visible and emission spectroscopy, NMR, ATR-FTIR, cyclic voltammetric studies, and density functional theory (DFT) calculations (where tctpy = 4,4‘4‘ ‘-tricarboxy-2,2‘:6‘,2‘ ‘-terpyridine, tfpbd = 4,4,4-trifluoro-1-(phenyl)butane-1,3-dione, tffpbd = 4,4,4-trifluoro-1- (4-fluorophenyl)butane-1,3-dione, and tfcpbd = 4,4,4-trifluoro-1-(4-chlorophenyl)butane-1,3-dione). In ethanol−methanol solution, these complexes exhibit intense visible light absorption, with low-energy MLCT band maxima above 600 nm. A distinct shoulder at around 680 nm improved red-light absorptivity beyond 680 nm. Controlled shifting of the low-energy MLCT band and Ru oxidation potential can be achieved by changing the electron donor ability of the β-diketonate ligand using various aryl substituents of the β-diketonate ligand with differing electron-donating strengths. Density functional theory (DFT) calculation of complex 2 shows that the HOMO is localized on the NCS ligand and the LUMO on the tctpy ligand, which is anchored to the TiO2 nanoparticles. The aryl-substituted β-diketonato-ruthenium(II)-polypyridyl sensitizers, when anchored to nanocrystalline TiO2 films, achieve very efficient sensitization, with greater than 80% incident photon-to-current conversion efficiency (IPCE) in the whole visible range extending up to 950 nm. Under standard AM 1.5 irradiation (100 mW cm-2) and using an electrolyte consisting of 0.6 M dimethylpropyl-imidazolium iodide, 0.05 M I2, 0.1 M LiI, and 0.07 M tert-butylpyridine in acetonitrile, a solar cell containing complex 2 yielded a short-circuit photocurrent density of 19.1 mA cm-2, an open-circuit photovoltage of 0.66 V, and a fill factor of 0.72, corresponding to an overall conversion efficiency of 9.1%.

Bimolecular electron and energy transfer reactivity of exchange-coupled dinuclear iron(III) complexes.

Bimolecular quenching between photosensitizers and exchange-coupled transition metal complexes has been studied in an effort to experimentally establish a link between Heisenberg spin exchange and chemical reactivity. The acceptors are members of the oxo/hydroxo-biscarboxylato class of dinuclear Fe(III) compounds, where protonation of the oxo bridge provides a means for modulating the magnitude of spin exchange within the cluster. Photoexcitation of solutions containing Ru(II) polypyridyl sensitizers and the Fe(III) complexes results in quenching of emission from the (3)MLCT excited state of the Ru(II) chromophores; nanosecond time-resolved absorption measurements demonstrate that quenching occurs, in part, by electron transfer. Decoupling electron transfer driving force (DeltaG(0)(ET)) from changes in the magnitude of spin exchange was achieved by varying the bridging carboxylate to afford a series of complexes of the form [Fe(2)O(H)(O(2)CR)(2)(Tp)(2)](n)(+) (n = 0, 1, 2). Electrochemical measurements reveal a greater than 500 mV shift in cluster reduction potential across the series (i.e., R = CH(3) to CF(3)), whereas variable-temperature magnetic susceptibility measurements demonstrate a corresponding invariance in spin exchange between the metal centers (J(oxo) = -119 +/- 4 cm(-1) and J(hydroxo) = -18 +/- 2 cm(-1) for H = -2JS(1).S(2)). Structural analyses suggest that reorganization energies (lambda) associated with electron transfer should be identical for all molecules within a given series (i.e., oxo or hydroxo bridged); likewise Deltalambda between the series is expected to be small. A comparison of quenching rates for the two extended series firmly establishes that neither reorganization energy nor electron transfer driving force considerations can account for differences in reactivity between oxo-bridged (large spin exchange) and hydroxo-bridged (small spin exchange) quenchers. Upon consideration of energy transfer contributions, it is determined that reactivity differences between the oxo- and hydroxo-bridged quenchers must lie in the relative rates of Dexter energy transfer and/or electron transfer, with the origin of the latter linked to something other than DeltaG(0)(ET) or lambda. Finally, the extent to which spin exchange within the dinuclear Fe(III) quenchers can be identified as the key variable influencing these reactivity patterns is discussed.

Sensitization of nanocrystalline TiO2 film by ruthenium(II) diimine dithiolate complexes

Abstract A new series of ruthenium(II) polypyridyl sensitizers with strongly electron donating dithiolate ligands Ru(dcbpy)2(L) and Ru(dcphen)2(L) where L is quinoxaline-2,3-dithiolate (qdt) or ethyl-2-cyano-3,3-dimercaptoacrylate (ecda) or 1,2-benzenedithiolate (bdt) or 3,4-toluenedithiolate (tdt), dcbpy is 4,4′-dicarboxy-2,2′-bipyridine, and dcphen is 4,7-dicarboxy-1,10-phenanthroline have been prepared for sensitization of nanocrystalline TiO2 electrodes. All the complexes exhibit a broad metal-to-ligand charge transfer absorption band over the whole visible range. The low-energy absorption bands and the Ru(II)/(III) oxidation potentials in these complexes could be tuned to about 150 nm and 600 mV, respectively, by choosing appropriate dithiolate ligands. When anchored to nanocrystalline titanium dioxide electrodes for light to electrical energy conversion in regenerative photoelectrochemical cells with I−/I3− acetonitrile electrolyte, these complexes show different sensitization to TiO2 electrodes with increasing activity in the sequence L=tdt, bdt, ecda, qdt. Both Ru(dcbpy)2(qdt) and Ru(dcphen)2(qdt) show overall cell efficiency (η) of about 3–4%, due to incident photon to current conversion efficiency of around 40–45% at 500 nm. The low cell efficiency of ecda complexes may be due to slow regeneration of the dye by electron donation from iodide following charge injection into TiO2.

Synthesis and photoelectric studies of Ru(II) polypyridyl sensitizers

New cis-Ru(3,3′-dcbpy) 2(NCS) 2 photosensitizer (where 3,3′-dcbpy is 3,3′-dicarboxy-2,2′-bipyridine) was synthesized using Ru(DMSO) 4Cl 2 as a starting material and characterized. Its photophysical and redox properties were compared with those of cis-Ru(4,4′-dcbpy) 2(NCS) 2 and cis-Ru(5,5′-dcbpy) 2(NCS) 2.The photoelectrochemical properties of the three dyes adsorbed on the surface of the nanocrystalline TiO 2 electrodes as well as on self-assembly monolayers (SAMs) were investigated. The photocurrents generated by sensitized TiO 2 electrodes were much higher than those by SAMs. And cis-Ru(4,4′-dcbpy) 2 showed a most efficient photosensitizer in both systems. The mechanism is discussed in the paper.

Reductive quenching of ruthenium polypyridyl sensitizers by cyanometalate complexes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReductive quenching of ruthenium polypyridyl sensitizers by cyanometalate complexesThomas E. Mallouk, Jonathan S. Krueger, James E. Mayer, and Christopher M. G. DymondCite this: Inorg. Chem. 1989, 28, 18, 3507–3510Publication Date (Print):September 1, 1989Publication History Published online1 May 2002Published inissue 1 September 1989https://doi.org/10.1021/ic00317a023RIGHTS & PERMISSIONSArticle Views227Altmetric-Citations18LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (576 KB) Get e-Alerts Get e-Alerts