| 1. |
- Franchi, Daniele, et al.
(författare)
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Applications of Sensitized Semiconductors as Heterogeneous Visible-Light Photocatalysts in Organic Synthesis
- 2020
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 8:41, s. 15405-15429
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Tidskriftsartikel (refereegranskat)abstract
- The industrial transition to more-sustainable chemical manufacturing requires the development of a variety of high-performance heterogeneous catalysts. Recently, new classes of heterogeneous and recyclable catalysts that exploit visible-light activation have emerged in the field of organic synthesis. Among these systems, sensitized semiconductors occupy a strategic place as they are able to initiate single electron transfer processes under heterogeneous conditions and using medium-to-low energy light activation. This technology can promote a range of synthetically useful reactions, such as oxidations, reductions, or additions, including C-C bond formation, under very mild conditions and with high selectivity. Sensitized semiconductors have been known for decades in solar cell technologies (the so-called "Dye-Sensitized Solar Cells") but applications in organic synthesis are only very recent. This Review provides a comprehensive overview of the mechanisms, reactivity, and scope of this technology, with a focus on their new and promising synthetic applications.
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| 2. |
- Franchi, Daniele, et al.
(författare)
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Effect of the Ancillary Ligand on the Performance of Heteroleptic Cu(I) Diimine Complexes as Dyes in Dye-Sensitized Solar Cells
- 2022
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 5:2, s. 1460-1470
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Tidskriftsartikel (refereegranskat)abstract
- A series of heteroleptic Cu(I) diimine complexes with different ancillary ligands and 6,6'-dimethyl-2,2'-bipyridine-4,4'-dibenzoic acid (dbda) as the anchoring ligand were selfassembled on TiO2 surfaces and used as dyes for dye-sensitized solar cells (DSSCs). The binding to the TiO2 surface was studied by hard X-ray photoelectron spectroscopy for a brominecontaining complex, confirming the complex formation. The performance of all complexes was assessed and rationalized on the basis of their respective ancillary ligand. The DSSC photocurrent-voltage characteristics, incident photon-to-current conversion efficiency (IPCE) spectra, and calculated lowest unoccupied molecular orbital (LUMO) distributions collectively show a push-pull structural dye design, in which the ancillary ligand exhibits an electron-donating effect that can lead to improved solar cell performance. By analyzing the optical properties of the dyes and their solar cell performance, we can conclude that the presence of ancillary ligands with bulky substituents protects the Cu(I) metal center from solvent coordination constituting a critical factor in the design of efficient Cu(I)-based dyes. Moreover, we have identified some components in the I-/I-3(-)-based electrolyte that causes dissociation of the ancillary ligand, i.e., TiO2 photoelectrode bleaching. Finally, the detailed studies on one of the dyes revealed an electrolyte-dye interaction, leading to a dramatic change of the dye properties when adsorbed on the TiO2 surface.
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| 3. |
- Franchi, Daniele, et al.
(författare)
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Synthesis and Characterization of New Organic Dyes Containing the Indigo Core
- 2020
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Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 25:15, s. 3377-
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Tidskriftsartikel (refereegranskat)abstract
- A new series of symmetrical organic dyes containing an indigo central core decorated with different electron donor groups have been prepared, starting from Tyrian Purple and using the Pd-catalyzed Stille-Migita coupling process. The effect of substituents on the spectroscopic properties of the dyes has been investigated theoretically and experimentally. In general, all dyes presented intense light absorption bands, both in the blue and red regions of the visible spectrum, conferring them a bright green color in solution. Using the same approach, an asymmetrically substituted D-A-pi-A green dye, bearing a triarylamine electron donor and the cyanoacrylate acceptor/anchoring group, has been synthesized for the first time and fully characterized, confirming that spectroscopic and electrochemical properties are consistent with a possible application in dye-sensitized solar cells (DSSC).
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| 4. |
- Leandri, Valentina, et al.
(författare)
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Exploring the Optical and Electrochemical Properties of Homoleptic versus Heteroleptic Diimine Copper(I) Complexes
- 2019
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Ingår i: Inorganic Chemistry. - : AMER CHEMICAL SOC. - 0020-1669 .- 1520-510X. ; 58:18, s. 12167-12177
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Tidskriftsartikel (refereegranskat)abstract
- Due to ligand scrambling, the synthesis and investigation of the properties of heteroleptic Cu(I) complexes can be a challenging task. In this work, we have studied the optical and electrochemical properties of a series of homoleptic complexes, such as [Cu(dbda)(2)](+), [Cu(dmp)(2)](+), [Cu(Br-dmp)(2)](+), [Cu(bcp)(2)](+), [Cu(dsbtmp)(2)](+), [Cu(biq)(2)](+), and [Cu(dap)(2)](+) in solution, and those of their heteroleptics [Cu(dbda)(dmp)](+), [Cu(dbda)(Br-dmp)](+), [Cu(dbda)(bcp)](+), [Cu(dbda)(dsbtmp))(+), [Cu(dbda)(biq)](+), [Cu(dbda)(dap)](+) adsorbed on the surface of anatase TiO2 (dbda = 6,6'-dimethyl-2,2'-bipyridine-4,4'-dibenzoic acid; dmp = 2,9-dimethyl-1,10-phenanthroline; Br-dmp = 5-bromo 2,9-dimethyl-1,10-phenanthroline; bcp = bathocuproine or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline; dsbtmp = 2,9-di(sec-butyl)-3,4,7,8-tetramethyl-1,10-phenanthroline; biq = 2,2'-biquinoline; dap = 2,9-dianisyl-1,10-phenanthroline). We show that the maximum absorption wavelengths of the heteroleptic complexes on TiO2 can be reasonably predicted from those of the homoleptic complexes in solution through a simple linear relation, whereas the prediction of their redox properties is less trivial. In the latter case, two different linear patterns emerge: one including the ligands bcp, biq, and dap and another one including the ligands dmp, Br-dmp, and dsbtmp. We offer an interpretation of the data based on the chemical structure of the ligands. On one hand, ligands bcp, biq, and dap possess a more extended pi-conjugated system, which gives a more prominent contribution to the overall redox properties of the ligand dbda. On the other hand, the ligands dmp, Br-dmp, and dsbtmp are all phenanthroline-based containing alkyl substituents and contribute less than dbda to the overall redox properties.
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| 5. |
- Saavedra, Valeria, 1985, et al.
(författare)
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Ionic Liquid-Induced Local Charge Compensation: Effects on Back Electron-Transfer Rates in Dye-Sensitized TiO2 Thin Films
- 2016
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:36, s. 20016-20023
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Tidskriftsartikel (refereegranskat)abstract
- The effect of ionic liquid electrolytes on back electron-transfer rates for dye-sensitized TiO2 thin films was investigated using microsecond millisecond transient absorption. For D35/TiO2 and [Ru(dcb)(3)](2+)/TiO2 in electrolytes based on 1-alkyl-3-methyl-imidazolium hexafluorophosphate, significantly slower back electron-transfer rates, compared to those observed in neat acetonitrile (CH3CN) and LiClO4/CH3CN, were found. Surprisingly, no such trends were observed for N3/TiO2 under the same conditions. This inconsistency points to the need for mechanistic understanding of how the structure and properties of dyes affect the electrolyte dye interface interactions in ionic liquid (IL) based dye-sensitized solar cells (DSSCs). To explain the observed behavior we propose an electrostatic effect at the TiO2 electrolyte interface, where the bulky IL cations rearrange at the TiO2 surface, locally compensating the charge. This would be consistent with N3 behaving differently because of its negatively charged SCN-ligands. This accumulation of cations at the interface affects the interaction between conduction band TiO2 electrons and the oxidized dye. As a result, slower back electron-transfer rates are observed when charge is effectively compensated. Therefore, here, the study of back electron-transfer kinetics was used as an indirect probe of local charge compensation at the dye semiconductor electrolyte interfaces. The results show that the mechanism of local charge compensation is dependent on dye structure.
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| 6. |
- Yao, Zhaoyang, et al.
(författare)
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Energy-Loss Reduction as a Strategy to Improve the Efficiency of Dye-Sensitized Solar Cells
- 2019
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Ingår i: Solar RRL. - : WILEY-V C H VERLAG GMBH. - 2367-198X. ; 3:10
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Tidskriftsartikel (refereegranskat)abstract
- Four weak donor backbones (BT, BTP, BT2, and BT3), featuring stepwise enhanced electron-donating capacities, are designed and synthesized. The sp(3) type carbons introduced are tethered with auxiliary groups to generate a better electron-blocking stereoscopic structure. A series of NB dyes are subsequently synthesized from these central cores by end-capping a strong diphenylamine donor and a planar heterocyclic acceptor 4-(benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic acid. The fine-tuning of steric configurations and energy levels of the resulting dye molecules reduces the energy losses significantly when applied in dye-sensitized solar cells. These devices offer one of the highest open-circuit voltages (approximate to 1.03 V) reported so far, and high power conversion efficiencies of 9.6%-12.1% using the NB dyes in combination with a well-developed cobalt-tris(4-methoxyphenyl)amine-based tandem electrolyte.
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| 7. |
- Zani, Lorenzo, et al.
(författare)
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Transition metal-catalyzed cross-coupling methodologies for the engineering of small molecules with applications in organic electronics and photovoltaics
- 2019
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Ingår i: Coordination chemistry reviews. - : Elsevier. - 0010-8545 .- 1873-3840. ; 392, s. 177-236
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Forskningsöversikt (refereegranskat)abstract
- Cross-coupling reactions have played a key role in producing numerous types of it-conjugated small molecules having appealing properties for practical applications in organic electronics, especially in the field of photovoltaics. The main advantages of such synthetic methodology are the compatibility with many types of functional groups and the flexibility which allows an easy way to introduce diversity and tune the electronic and photophysical properties of the target molecules. As a result, many semiconducting and photoactive organic compounds have been synthesized using this powerful tool. In this paper we will highlight a number of selected syntheses and optimized C-C bond formation processes described in the years 2000-2018 and related to this specific field, choosing those examples which can demonstrate the enormous power of the cross-coupling processes, but also the room for improvements of these methodologies.
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