| 1. |
- Adranno, Brando, et al.
(författare)
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Broadband white-light-emitting electrochemical cells
- 2023
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Ingår i: Advanced Photonics Research. - : John Wiley & Sons. - 2699-9293. ; 4:5
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Tidskriftsartikel (refereegranskat)abstract
- Emerging organic light-emitting devices, such as light-emitting electrochemical cells (LECs), offer a multitude of advantages but currently suffer from that most efficient phosphorescent emitters are based on expensive and rare metals. Herein, it is demonstrated that a rare metal-free salt, bis(benzyltriphenylphosphonium)tetrabromidomanganate(II) ([Ph3PBn]2[MnBr4]), can function as the phosphorescent emitter in an LEC, and that a careful device design results in the fact that such a rare metal-free phosphorescent LEC delivers broadband white emission with a high color rendering index (CRI) of 89. It is further shown that broadband emission is effectuated by an electric-field-driven structural transformation of the original green-light emitter structure into a red-emitting structure.
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| 2. |
- Adranno, Brando, et al.
(författare)
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The 8-hydroxyquinolinium cation as a lead structure for efficient color-tunable ionic small molecule emitting materials
- 2023
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Ingår i: Advanced Photonics Research. - : John Wiley & Sons. - 2699-9293. ; 4:3
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Tidskriftsartikel (refereegranskat)abstract
- Albeit tris(8-hydroxyquinolinato) aluminum (Alq3) and its derivatives are prominent emitter materials for organic lighting devices, and the optical transitions occur among ligand-centered states, the use of metal-free 8-hydroxyquinoline is impractical as it suffers from strong nonradiative quenching, mainly through fast proton transfer. Herein, it is shown that the problem of rapid proton exchange and vibration quenching of light emission can be overcome not only by complexation, but also by organization of the 8-hydroxyquinolinium cations into a solid rigid network with appropriate counter-anions (here bis(trifluoromethanesulfonyl)imide). The resulting structure is stiffened by secondary bonding interactions such as pi-stacking and hydrogen bonds, which efficiently block rapid proton transfer quenching and reduce vibrational deactivation. Additionally, the optical properties are tuned through methyl substitution from deep blue (455 nm) to blue-green (488 nm). Time-dependent density functional theory (TDFT) calculations reveal the emission to occur from which an unexpectedly long-lived S-1 level, unusual for organic fluorophores. All compounds show comparable, even superior photoluminescence compared to Alq3 and related materials, both as solids and thin films with quantum yields (QYs) up to 40-50%. In addition, all compounds show appreciable thermal stability with decomposition temperatures above 310 °C.
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| 3. |
- Bousrez, Guillaume, et al.
(författare)
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Ionic Liquid-Based Dye-Sensitized Solar Cells-Insights into Electrolyte and Redox Mediator Design
- 2021
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 9:24, s. 8107-8114
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Tidskriftsartikel (refereegranskat)abstract
- A series of asymmetric and symmetric 1,3-dialkyltriazolium iodides were studied with hindsight to their application as electrolytes and redox mediators in dye-sensitized solar cells (DSSCs). Compounds with an alkyl chain length from C4 to C10 present the characteristics of ionic liquids (ILs), whilst those with longer chains exhibit liquid crystallinity. All compounds show an appreciable chemical and thermal stability with decomposition temperatures around 185–195 °C. Testing these compounds as electrolytes and redox mediators in DSSCs reveals significant changes in the properties of the electrolyte upon addition of the redox couple. Addition of iodine generally leads to a depression of the melting point and an enhancement of conductivity. These changes in the electrolyte, which are significant, have so far been largely overlooked in DSSC optimization. Furthermore, in comparison to frequently employed imidazolium iodides, 1-alkyl-3-methyltriazolium iodides show both an improved superior efficiency and an extended cell lifetime. This is attributed to the fact that, unlike the imidazolium salts, the triazolium counterparts are not hygroscopic. The nonhygroscopic nature of the salts also renders device fabrication easier. In addition, electrode passivation, which is commonly observed with imidazolium iodides, could not be noticed for the triazolium analogues, making these materials overall extremely attractive.
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| 4. |
- Bousrez, Guillaume, et al.
(författare)
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Magnetic, Photo- and Electroluminescent : Multifunctional Ionic Tb Complexes
- 2021
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 60:23, s. 17487-17497
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Tidskriftsartikel (refereegranskat)abstract
- In the search for new multifunctional materials, particularly for application in solid-state lighting, a set of terbium salicylato (Sal) complexes of general composition [Cat][Tb(Sal)4] with the commonly ionic liquid-forming (IL) cations [Cat] = (2-hydroxyethyl)trimethylammonium (choline) (Chol+), diallyldimethylammonium (DADMA+), 1-ethyl-3-methylimidazolium (C2C1Im+), 1-butyl-3-methylimidazolium (C4C1Im+), 1-ethyl-3-vinylimidazolium (C2Vim+), and tetrabutylphosphonium (P4444+) were synthesized. All Tb compounds exhibit strong green photoluminescence of high color purity by energy transfer from the ligand in comparison with what the analogous La compounds show, and quantum yields can reach up to 63% upon ligand excitation. When excited with an HF generator, the compounds show strong green electroluminescence with the same features of mission. The findings promise a high potential of application as emitter materials in solid-state lighting. As an additional feature, the Tb compounds show a strong response to applied external fields, rendering them multifunctional materials.
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| 5. |
- Bousrez, Guillaume, et al.
(författare)
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Ready Access to Anhydrous Anionic Lanthanide Acetates by Using Imidazolium Acetate Ionic Liquids as the Reaction Medium
- 2021
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 27:52, s. 13181-13189
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Tidskriftsartikel (refereegranskat)abstract
- Access to lanthanide acetate coordination compounds is challenged by the tendency of lanthanides to coordinate water and the plethora of acetate coordination modes. A straightforward, reproducible synthetic procedure by treating lanthanide chloride hydrates with defined ratios of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C(2)mim][OAc]) has been developed. This reaction pathway leads to two isostructural crystalline anhydrous coordination complexes, the polymeric [C(2)mim](n)[{Ln(2)(OAc)(7)}(n)] and the dimeric [C(2)mim](2)[Ln(2)(OAc)(8)], based on the ion size and the ratio of IL used. A reaction with an IL : Ln-salt ratio of 5 : 1, where Ln=Nd, Sm, and Gd, led exclusively to the polymer, whilst for the heaviest lanthanides (Dy-Lu) the dimer was observed. Reaction with Eu and Tb resulted in a mixture of both polymeric and dimeric forms. When the amount of IL and/or the size of the cation was increased, the reaction led to only the dimeric compound for all the lanthanide series. Crystallographic analyses of the resulting salts revealed three different types of metal-acetate coordination modes where eta(2)mu kappa(2) is the most represented in both structure types.
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| 6. |
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| 7. |
- Renier, Olivier, et al.
(författare)
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Developing design tools for introducing and tuning structural order in ionic liquids
- 2021
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 23:8, s. 1785-1795
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Tidskriftsartikel (refereegranskat)abstract
- Ionic liquids (ILs) are receiving growing interest as highly tunable, multifunctional materials. Remarkably for liquids, they tend to display a high level of structural order. This structural order may even lead to the formation of mesophases such as liquid crystals (LCs). Imidazolium compounds are by far the most popular ILs, because they offer a widely versatile platform for property tuning. To investigate what is driving structural order in imidazolium-based ILs a series of asymmetrical 1-dodecyl-2-methyl-3-alkylimidazolium bromides, [C(12)C(1)C(n)im][Br] with n = 0-12 have been synthesized, fully characterized and their structures and properties compared with the analogous 1-dodecyl-3-alkylimidazolium as well as the 1,2,3-triazolium bromides. The aim is to examine the influence of the replacement of the most acidic 2-H proton on the imidazolium head group by methylation on the properties and structure of ILs. For all compounds, except for compounds with butyl- and hexyl-chains as well as the protonated species, mesophase formation can be observed. Obviously, the simple presence of long alkyl chains such as dodecyl (a design concept frequently put forward in the literature) is not sufficient to support mesophase formation alone. Rather, for the formation of a liquid crystalline phase, a balance between attractive van der Waals forces, hydrogen bonds, and electrostatic interactions is required. Data from temperature-dependent small-angle X-ray scattering (SAXS) and polarizing optical microscopy (POM) suggest three different cation conformations for the studied [C(12)C(1)C(n)im][Br]: cations with 0 <= n <= 4 exhibit a near-linear conformation; for 5 <= n <= 10 a V-shape is adopted, and for n = 11 or 12 a U-shape is found. We demonstrated that the structural possibility for an interdigitation of the long chains is an influential factor for the formation of a mesophase.
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| 8. |
- Renier, Olivier, 1995-
(författare)
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Exploring The Versatility Of Ionic Liquids : From fundamental understanding to materials inspired from ionic liquids
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ionic liquids (ILs) have gained popularity as “green” and safe replacements for conventional organic solvents. They are defined as ionic salts displaying a melting point below 100 °C. Some of their unique characteristics also include negligible vapour pressure, good electrical conductivity as well as good thermal and chemical stability. While their “green” nature has since been disputed, they can be used and applied in many additional fields, such as solar energy production, new lighting technology and much more. In this thesis, the aim is to gain fundamental knowledge on ILs, specifically their structures and behaviour, in order to design materials tailored for specific applications. We also aim to use ILs to access otherwise difficult to synthesize materials and study their properties and applications.The thermal properties of ILs are one of their most important characteristics. However, it is still poorly understood how the structural aspects of ILs influence their particular thermal behaviour. By studying different systems, we derived relationships between the structure and the thermal behaviour of ILs. Hydrogen bonding and other supramolecular interactions play a major role in controlling both the melting temperature and the IL's ability to support a liquid crystalline mesophase. This control was shown both in a series of ILs based on 1-alkyl-3-dodecylimidazolium bromide and in a series of ILs based on azobenzene-imidazolium compounds.The stability issues associated with the electrolytes used in dye-sensitized solar cells (DSSCs) present a major disadvantage. We tested using ILs as electrolytes to avoid this problem. In our study, we used 1,3-dialkyltriazolium ILs as electrolytes in combination with the iodide redox couple, and not only was the stability of the DSSC improved but also the performance of IL-based DSSCs.Efficient luminescent materials are always sought after. Using ILs in combination with lanthanides, we achieved highly luminescent compounds as well as some magnetic ones. ILs can also be used to access anhydrous forms of otherwise hydrophilic species, such as ions of the lanthanides. We have used acetate ILs to attain water free complexes of the ions from the whole lanthanide series, starting from the hydrated species. This simple process could be applied to more species of hydrophilic metals that are otherwise known to form hydrates.Finally, the ligand obtained through ILs, 1,3-diethylimidazole-2-thione was used to aid in the studying of phase transitions when combined with zinc chloride (ZnCl2). It helped to reveal a yet unseen amorphous step in the solid-solid phase transition from a single crystal into another one, where morphology of the particle was preserved. I forsee that more fundamental structural studies can be conducted by forcing the coordination of the soft-donor nitrogen onto lanthanides by using dicyanamide ILs in the future.
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| 9. |
- Renier, Olivier, et al.
(författare)
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Investigation of the role of hydrogen bonding in ionic liquid-like salts with both N- and S-soft donors
- 2023
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 25:4, s. 530-540
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Tidskriftsartikel (refereegranskat)abstract
- In search of ionic liquids (ILs) with multiple types of soft donor atoms capable of preferentially complexing a range of soft metal ions over harder ions, we investigated structural clues to the role of hydrogen bonding in IL behavior through a series of salts with anions containing both N- and S-donor atoms based on azole thiolates. Reaction of equimolar amounts of triethylamine (Et3N) or diisobutylamine (DBA) with 1-phenyl-1H-tetrazole-5-thiol (PhTzSH), 1-methyl-1H-tetrazole-5-thiol (MeTzSH), or 5-methyl-1,3,4-dithiazole-2-thiol (MeDiTSH) yielded [Et3NH][MeTzS] (1), a yellow liquid, and the low melting yellow solids [DBAH][MeTzS] (2), [Et3NH][PhTzS] (3), [DBAH][PhTzS] (4), [Et3NH][MeDiTS] (5), and [DBAH][MeDiTS] (6). Thermal analysis revealed that all of them qualify as ILs with melting points below 100 °C. Single crystal X-ray structure analysis of 2–6 revealed the presence of an extensive H-bonding network that includes the rare N–H⋯S hydrogen bonds in 3, 4, and 6. These weaker interactions appear to significantly influence thermal behavior, where strong bonding leads to higher melting temperatures and lower decomposition points.
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| 10. |
- Renier, Olivier, et al.
(författare)
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Photoisomerization and Mesophase Formation in Azo-Ionic Liquids
- 2020
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 20:1, s. 214-225
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Tidskriftsartikel (refereegranskat)abstract
- Ionic liquids present a versatile, highly tunable class of soft functional materials. Aside from being low melting salts, they can be endowed with additional functionalities. In N-alkylimidazolium halides, which are a prominent class of ionic liquids (ILs), the imidazolium cation was linked via an ether-bridge to an azobenzene unit in order to obtain photoresponsive materials through photoinduced trans-cis isomerization. The azobenzene unit, in turn, was modified with electron-donating or -withdrawing groups such as methyl-, tert-butyl-, methoxy-, N,N-dimethylamino, and nitro groups to study their influence on the photoisomerization and phase behavior. Endowing the imidazolium additionally with a long alkyl chain allows the materials to potentially form liquid crystalline (LC) mesophases before melting into the isotropic liquid. All studied compounds qualify as ionic liquids, and all, except for the nitro-compound, show the formation of smectic mesophases melting to the isotropic liquid. The compounds with the bulkiest aliphatic substituent, the tert-butyl, shows the lowest melting point, the largest mesophase window, and an efficient photochemical trans-cis conversion (>90%). In summary, by tuning sterically and electronically the cationic part of ILs, a photoswitchable room temperature liquid crystal could be developed and design guidelines for photoresponsive ionic liquids could be obtained.
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