- Efficient panchromatic sensitization of nanocrystalline TiO2 films by a black dye based on a trithiocyanato-ruthenium complex
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A black trithiocyanato-ruthenium(II) terpyridyl complex where the terpyridyl ligand is substituted by three carboxyl groups in 4,4′,4″-positions achieves very efficient panchromatic sensitization of nanocrystalline TiO2 solar cells over the whole visible range extending into the near-IR region up to 920 nm.
- Nazeeruddin,Pechy,Graetzel
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- Engineering of efficient panchromatic sensitizers for nanocrystalline TiO2-based solar cells
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A new series of panchromatic ruthenium(II) sensitizers derived from carboxylated terpyridyl complexes of tris-thiocyanato Ru(II) have been developed. Black dye containing different degrees of protonation {(C2H5)3NH}[Ru(H3tcterpy)(NCS) 3] 1, {(C4H9)4N}2[Ru(H2 tcterpy)(NCS)3] 2, {(C4H9)4N}3[Ru(Htcterpy)(NCS) 3] 3, and {(C4H9)4N}4[Ru(tcterpy)(NCS) 3] 4 (tcterpy = 4,4′,4″-tricarboxy-2,2′:6′,2″-terpyridine) have been synthesized and fully characterized by UV-vis, emission. IR, Raman, NMR, cyclic voltammetry, and X-ray diffraction studies. The crystal structure of complex 2 confirms the presence of a RuIIN6 central core derived from the terpyridine ligand and three N-bonded thiocyanates. Intermolecular H-bonding between carboxylates on neighboring terpyridines gives rise to 2-D H-bonded arrays. The absorption and emission maxima of the black dye show a bathochromic shift with decreasing pH and exhibit pH-dependent excited-state lifetimes. The red-shift of the emission maxima is due to better π-acceptor properties of the acid form that lowers the energy of the CT excited state. The low-energy metal-to-ligand charge-transfer absorption band showed marked solvatochromism due to the presence of thiocyanate ligands. The Ru(II)/(III) oxidation potential of the black dye and the ligand-based reduction potential shifted cathodically with decreasing number of protons and showed more reversible character. The adsorption of complex 3 from methoxyacetonitrile solution onto transparent TiO2 films was interpreted by a Langmuir isotherm yielding an adsorption equilibrium constant, Kads, of (1.0 ± 0.3) × 105 M-1. The amount of dye adsorbed at monolayer saturation was (na = 6.9 ± 0.3) × 10-8 mol/mg of TiO2, which is around 30% less than that of the cis-di(thiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylate) ruthenium(II) complex. The black dye, when anchored to nanocrystalline TiO2 films achieves very efficient sensitization over the whole visible range extending into the near-IR region up to 920 nm, yielding over 80% incident photon-to-current efficiencies (IPCE). Solar cells containing the black dye were subjected to analysis by a photovoltaic calibration laboratory (NREL, U.S.A.) to determine their solar-to-electric conversion efficiency under standard AM 1.5 sunlight. A short circuit photocurrent density obtained was 20.5 mA/cm2, and the open circuit voltage was 0.72 V corresponding to an overall conversion efficiency of 10.4%.
- Nazeeruddin,Pechy,Renouard,Zakeeruddin,Humphry-Baker,Cointe,Liska,Cevey,Costa,Shklover,Spiccia,Deacon,Bignozzi,Graetzel
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- A more efficient synthesis of 4,4′,4″-tricarboxy-2,2′: 6′,2″-terpyridine
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We report in this paper a new route for the synthesis of 4,4′,4″-tricarboxy-2,2′:6′,2″-terpyridine. This synthetic pathway has a lower ecological impact with respect to yield, atom economy, solvent and chemicals used and wastes generated when compared to a previously reported method. In addition it uses furfural, which can be obtained from renewable sources. The title compound can be used to prepare complexes that are valuable for applications in Dye Sensitized Solar Cells.
- Dehaudt, Jeremy,Husson, Jerome,Guyard, Laurent
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- Near-Infrared-to-Visible Photon Upconversion Sensitized by a Metal Complex with Spin-Forbidden yet Strong S0-T1 Absorption
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Near-infrared (NIR)-to-visible (vis) photon upconversion (UC) is useful for various applications; however, it remains challenging in triplet-triplet annihilation-based UC, mainly due to the energy loss during the S1-to-T1 intersystem crossing (ISC) of molecular sensitizers. In this work, we circumvent this energy loss by employing a sensitizer with direct S0-to-T1 absorption in the NIR region. A mixed solution of an osmium complex having a strong S0-T1 absorption and rubrene emitter upconverts NIR light ( = 938 nm) to visible light ( = 570 nm). Sensitizer-doped emitter nanoparticles are prepared by re-precipitation and dispersed into an oxygen-barrier polymer. The obtained composite film shows a stable NIR-to-vis UC emission based on triplet energy migration (TEM), even in air. A high UC quantum yield of 3.1percent is observed for this TEM-UC system, expanding the scope of molecular sensitizers for NIR-to-vis UC.
- Amemori, Shogo,Sasaki, Yoichi,Yanai, Nobuhiro,Kimizuka, Nobuo
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- Electron-Equivalent Valency through Molecularly Well-Defined Multivalent DNA
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Oligonucleotide-functionalized nanoparticles (NPs), also known as "programmable atom equivalents"(PAEs), have emerged as a class of versatile building blocks for generating colloidal crystals with tailorable structures and properties. Recent studies have shown that, at small size and low DNA grafting density, PAEs can also behave as "electron equivalents"(EEs), roaming through and stabilizing a complementary PAE sublattice. However, it has been challenging to obtain a detailed understanding of EE-PAE interactions and the underlying colloidal metallicity because there is inherent polydispersity in the number of DNA strands on the surfaces of these NPs; thus, the structural uniformity and tailorability of NP-based EEs are somewhat limited. Herein, we report a strategy for synthesizing colloidal crystals where the EEs are templated by small molecules, instead of NPs, and functionalized with a precise number of DNA strands. When these molecularly precise EEs are assembled with complementary NP-based PAEs, X-ray scattering and electron microscopy reveal the formation of three distinct "metallic"phases. Importantly, we show that the thermal stability of these crystals is dependent on the number of sticky ends per EE, while lattice symmetry is controlled by the number and orientation of EE sticky ends on the PAEs. Taken together, this work introduces the notion that, unlike conventional electrons, EEs that are molecular in origin can have a defined valency that can be used to influence and guide specific phase formation.
- Cheng, Ho Fung,Wang, Shunzhi,Mirkin, Chad A.
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supporting information
p. 1752 - 1757
(2021/02/06)
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- Chromium(VI) oxide-mediated oxidation of polyalkyl-polypyridines to polypyridine-polycarboxylic acids with periodic acid
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4,4′-Dicarboxy-2,2′-bipyridine was synthesized quantitatively by chromium(VI) oxide-mediated oxidation of 4,4′-dimethyl-2,2′-bipyridine or 4,4′-diethyl-2,2′-bipyridine with periodic acid as the terminal oxidant in sulfuric acid. 5,5′-Dicarboxy-2,2′-bipyridine and 6,6’-dicarboxy-2,2′-bipyridine were also synthesized by the method from the corresponding dimethyl bipyridines in excellent yields. 4,4′,4″-Tricarboxy-2,2′:6′,2″-terpyridine was obtained in 80% yield from 4,4′,4″-triethyl-2,2′:6′,2″-terpyridine, and 4,4′,4″,4′″-tetracarboxy-2,2′:6′,2″:6″,2′″-quaterpyridine was obtained in 72% yield from 4,4′,4″,4′″-tetraethyl-2,2′:6′,2″:6″,2′″-quaterpyridine by the same procedure.
- Yamazaki, Shigekazu
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supporting information
p. 2210 - 2218
(2019/06/25)
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