| 1. |
- Corbet, Brian P., et al.
(författare)
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Peptide Conjugated Dihydroazulene/Vinylheptafulvene Photoswitches in Aqueous Environment
- 2023
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Ingår i: European Journal of Organic Chemistry. - : John Wiley & Sons. - 1434-193X .- 1099-0690. ; 26:1
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Tidskriftsartikel (refereegranskat)abstract
- Light-responsive molecules have seen a major advance in modulating biological functions in recent years. Especially photoswitches are highly attractive building blocks due to the reversible nature of their light-mediated reactivity. They are frequently used to affect both the properties of small bioactive compounds and biomacromolecules if incorporated suitably. Despite their success in a plethora of applications, only a limited set of photochromic core structures is routinely employed and a large number of photochromic couples are under-investigated in biological context. Broadening the toolbox of photoswitches available to modulate biological activity would open new avenues and unlock the full potential of photoswitchable molecules for biological studies. In this work, we explore the photochemical and thermal properties of the dihydroazulene/vinylheptafulvene photochromic couple as peptide conjugates in aqueous environment.
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| 2. |
- Cybularczyk-Cecotka, Martyna, et al.
(författare)
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Photocatalysis in Aqueous Micellar Media Enables Divergent C-H Arylation and N-Dealkylation of Benzamides
- 2022
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 12:6, s. 3543-3549
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Tidskriftsartikel (refereegranskat)abstract
- Photocatalysis in aqueous micellar media has recently opened wide avenues to activate strong carbon-halide bonds. So far, however, it has mainly explored strongly reducing conditions, restricting the available chemical space to radical or anionic reactivity. Here, we demonstrate a controllable, photocatalytic strategy that channels the reaction of chlorinated benzamides via either a radical or a cationic pathway, enabling a chemodivergent C-H arylation or N-dealkylation. The catalytic system operates under mild conditions with methylene blue as a photocatalyst and blue LEDs as the light source. Factors determining the reactivity of substrates, their selectivity, and preliminary mechanistic studies are presented.
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| 3. |
- Doellerer, Daniel, et al.
(författare)
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Highly Efficient Oxindole-Based Molecular Photoswitches
- 2023
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Ingår i: Chemistry - A European Journal. - : Wiley-VCH Verlagsgesellschaft. - 0947-6539 .- 1521-3765. ; 29:55
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Tidskriftsartikel (refereegranskat)abstract
- 3-Benzylidene-indoline-2-ones play a prominent role in the pharmaceutical industry due to the diverse biomedical applications of oxindole heterocycles. Despite the extensive reports on their biological properties, these compounds have hardly been studied for their photochemical activity. Here, we present 3-benzylidene-indoline-2-ones as a promising class of photoswitches with high yields, robust photochemical switching with quantum yields reaching up to 50 % and potential for biological applications. 3-Benzylidene-indoline-2-ones are of great importance for the pharmaceutical industry. These compounds have been extensively reported for their biological properties, but have hardly been studied concerning their photochemical activity. Here, we present 3-benzylidene-indoline-2-ones as a promising class of photoswitches with high yields, robust photochemical switching, and quantum yields reaching up to 50 %.image
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| 4. |
- Jurberg, Igor D., et al.
(författare)
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Visible Light-Enhanced C-H Amination of Cyclic Ethers with Iminoiodinanes
- 2022
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Ingår i: Advanced Synthesis and Catalysis. - : John Wiley & Sons. - 1615-4150 .- 1615-4169. ; 364:23, s. 4061-4068
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Tidskriftsartikel (refereegranskat)abstract
- A two-step protocol allowing the C-H amination of cyclic ethers with iminoiodinanes, followed by the reduction of the resulting intermediate has been developed for the preparation of amino alcohols. The initial C-H functionalization is accelerated by visible light, improving the reactivity compared to the thermal process performed in the dark. The effect of different substituents on the photochemical reactivity of iminoiodinanes has been studied both experimentally and computationally. Photophysical measurements and DFT calculations were performed to better understand the observed reactivities and corroborate the proposed mechanistic proposal.
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| 5. |
- Kathan, Michael, et al.
(författare)
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The Influence of Strain on the Rotation of an Artificial Molecular Motor
- 2022
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Ingår i: Angewandte Chemie International Edition. - : Wiley-VCH Verlagsgesellschaft. - 1433-7851 .- 1521-3773. ; 61:34
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Tidskriftsartikel (refereegranskat)abstract
- In artificial small-molecule machines, molecular motors can be used to perform work on coupled systems by applying a mechanical load-such as strain-that allows for energy transduction. Here, we report how ring strain influences the rotation of a rotary molecular motor. Bridging the two halves of the motor with alkyl tethers of varying sizes yields macrocycles that constrain the motor's movement. Increasing the ring size by two methylene increments increases the mobility of the motor stepwise and allows for fine-tuning of strain in the system. Small macrocycles (8-14 methylene units) only undergo a photochemical E/Z isomerization. Larger macrocycles (16-22 methylene units) can perform a full rotational cycle, but thermal helix inversion is strongly dependent on the ring size. This study provides systematic and quantitative insight into the behavior of molecular motors under a mechanical load, paving the way for the development of complex coupled nanomachinery.
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| 6. |
- Korzun, Andre, et al.
(författare)
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Replacing the BO in BODIPY : unlocking the path to SBDIPY and BIDIPY chromophores
- 2023
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Ingår i: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 14:24, s. 6579-6584
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Tidskriftsartikel (refereegranskat)abstract
- Boron-based dipyrrin chromophores (BODIPY) have found widespread application over the last twenty years in fields as diverse as medicine and materials. Thus, several efforts have been placed to exchange boron with other elements, with the aim of developing materials with complementary luminescent properties. However, despite these attempts, the incorporation of other main-group elements in dipyrrin scaffolds remains still rare. We have successfully synthesized and characterized novel chromophores based on antimony and bismuth, SBDIPY and BIDIPY. Solution stabilities have been investigated by VT-UV/vis spectroscopy and the fluorescence emission studied and supported by computational analysis. We were also able to isolate the first direct analogue of BODIPY containing fluoride handles, disclosing preliminary luminescent features.
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| 7. |
- Kuntze, Kim, et al.
(författare)
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A visible-light-driven molecular motor based on barbituric acid
- 2023
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Ingår i: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 14:32, s. 8458-8465
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Tidskriftsartikel (refereegranskat)abstract
- We present a class of visible-light-driven molecular motors based on barbituric acid. Due to a serendipitous reactivity we observed during their synthesis, these motors possess a tertiary stereogenic centre on the upper half, characterised by a hydroxy group. Using a combination of femto- and nanosecond transient absorption spectroscopy, molecular dynamics simulations and low-temperature H-1 NMR experiments we found that these motors operate similarly to push-pull second-generation overcrowded alkene-based molecular motors. Interestingly, the hydroxy group at the stereocentre enables a hydrogen bond with the carbonyl groups of the barbituric acid lower half, which drives a sub-picosecond excited-state isomerisation, as observed spectroscopically. Computational simulations predict an excited state "lasso" mechanism where the intramolecular hydrogen bond pulls the molecule towards the formation of the metastable state, with a high predicted quantum yield of isomerisation (68%) in gas phase.
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| 8. |
- Marcon, Michela, et al.
(författare)
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A dinuclear copper(ii) complex with photoswitchable catechol oxidation activity
- 2023
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Ingår i: Chemical Communications. - : Royal Society of Chemistry. - 1359-7345 .- 1364-548X. ; 59:7, s. 948-951
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we report the first example of a photoswitchable copper complex with catechol oxidase activity. The distance between the two copper centres is optimal for catalytic catechol oxidation in the Z-configuration. Thus, the activity of the catalyst is increased compared to its E-configuration.
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| 9. |
- Nitu, Cristina, et al.
(författare)
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Computational study on the reduction and solvolysis of triplet chlorobenzenes
- 2023
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Ingår i: Journal of Physical Organic Chemistry. - : John Wiley & Sons. - 0894-3230 .- 1099-1395. ; 36:1
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Tidskriftsartikel (refereegranskat)abstract
- In this work we explored the excited state reactivity of triplet chlorobenzenes with density functional theory and a cluster-continuum approach. We modeled two competing reactions: a direct abstraction of hydrogen from a solvent molecule and solvolysis via photo-SN2Ar. Electron donating (–OMe, –CH2SiMe3, –SiMe3) and withdrawing (–CN) substituents not only have distinct effects on the triplet geometries, inducing structural distortions due to the relief of excited state antiaromaticity, but also affect the reactivity of the system. Therefore, electron-rich chlorobenzenes favor the radical reduction, while electron deficiency opens the possibility for solvolysis. Both reactions are energetically comparable to or more favorable then the dissociation of the C-Cl bond to form triplet or singlet aryl cations, the intermediates considered responsible for these reactivities. Our findings can be correlated with experimental results on similar systems available from the literature, deeming the proposed pathways as viable alternatives to established mechanisms involving aryl cations.
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| 10. |
- Nitu, Cristina, et al.
(författare)
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Meta-Ortho Effect on the Excited State Pathways of Chloroanilines
- 2024
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Ingår i: European Journal of Organic Chemistry. - : John Wiley & Sons. - 1434-193X .- 1099-0690. ; 27:1
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Tidskriftsartikel (refereegranskat)abstract
- Direct excitation of aromatic compounds grants access to high-energy intermediates that can be utilised in organic synthesis. Understanding and predicting the substituent effects at the excited state for aromatic molecules remains challenging for the synthetic photochemist. In this work, we present an experimental and computational investigation of the excited state of the isomeric chloroanilines, which promptly react by losing the chloride when the amino group is in para position, but are non-reactive and non-emissive in the meta and ortho isomers. XMS-CASPT2//CASSCF computations explain this apparent contradiction of the meta-ortho selectivity rule of Zimmerman, which originates from the substituent effects lowering to a different extent the barrier to populate the prefulvenic conical intersection that deactivates non-radiatively the singlet excited state of the chloroanilines. Computational chemistry allows to elucidate the observed selectivity in the photochemistry of chloroanilines. A meta-ortho effect of the substituents favours the population of the prefulvenic conical intersection which leads to rapid deactivation of the m- and o-isomers of chloroaniline, while the para derivative lives long enough to emit and populate the reactive triplet state which leads to C-Cl dissociation.+image
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| 11. |
- Ovalle, Marco, et al.
(författare)
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Light-Fueled Transformations of a Dynamic Cage-Based Molecular System
- 2023
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Ingår i: Angewandte Chemie International Edition. - : John Wiley & Sons. - 1433-7851 .- 1521-3773. ; 62:9
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Tidskriftsartikel (refereegranskat)abstract
- In a chemical equilibrium, the formation of high-energy species-in a closed system-is inefficient due to microscopic reversibility. Here, we demonstrate how this restriction can be circumvented by coupling a dynamic equilibrium to a light-induced E/Z isomerization of an azobenzene imine cage. The stable E-cage resists intermolecular imine exchange reactions that would "open" it. Upon switching, the strained Z-cage isomers undergo imine exchange spontaneously, thus opening the cage. Subsequent isomerization of the Z-open compounds yields a high-energy, kinetically trapped E-open species, which cannot be efficiently obtained from the initial E-cage, thus shifting an imine equilibrium energetically uphill in a closed system. Upon heating, the nucleophile is displaced back into solution and an opening/closing cycle is completed by regenerating the stable all-E-cage. Using this principle, a light-induced cage-to-cage transformation is performed by the addition of a ditopic aldehyde.
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| 12. |
- Pfeifer, L., et al.
(författare)
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Controlling forward and backward rotary molecular motion on demand
- 2022
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Synthetic molecular machines hold tremendous potential to revolutionize chemical and materials sciences. Their autonomous motion controlled by external stimuli allows to develop smart materials whose properties can be adapted on command. For the realisation of more complex molecular machines, it is crucial to design building blocks whose properties can be controlled by multiple orthogonal stimuli. A major challenge is to reversibly switch from forward to backward and again forward light-driven rotary motion using external stimuli. Here we report a push-pull substituted photo-responsive overcrowded alkene whose function can be toggled between that of a unidirectional 2(nd) generation rotary motor and a molecular switch depending on its protonation and the polarity of its environment. With its simplicity in design, easy preparation, outstanding stability and orthogonal control of distinct forward and backward motions, we believe that the present concept paves the way for creating more advanced molecular machines. Being able to control motion at the molecular level is vital for many future developments in the molecular sciences. Here, the authors report the controlled forward and backward rotation of a molecular motor guided by external stimuli.
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| 13. |
- Pfeifer, Lukas, et al.
(författare)
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Dual-function artificial molecular motors performing rotation and photoluminescence
- 2022
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:44
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Tidskriftsartikel (refereegranskat)abstract
- Molecular machines have caused one of the greatest paradigm shifts in chemistry, and by powering artificial mechanical molecular systems and enabling autonomous motion, they are expected to be at the heart of exciting new technologies. One of the biggest challenges that still needs to be addressed is designing the involved molecules to combine different orthogonally controllable functions. Here, we present a prototype of artificial molecular motors exhibiting the dual function of rotary motion and photoluminescence. Both properties are controlled by light of different wavelengths or by exploiting motors' outstanding two-photon absorption properties using low-intensity near-infrared light. This provides a noninvasive way to both locate and operate these motors in situ, essential for the application of molecular machines in complex (bio)environments.
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| 14. |
- Sheng, Jinyu, et al.
(författare)
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Designing P-type bi-stable overcrowded alkene-based chiroptical photoswitches
- 2023
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Ingår i: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 14:16, s. 4328-4336
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Tidskriftsartikel (refereegranskat)abstract
- Overcrowded alkene based molecular motors and switches constitute a unique class of photo-responsive systems due to their intrinsic chirality near the core C(sic )C bond, making them highly suitable candidates for the construction of light-switchable dynamic systems, i.e., for controlling molecular motion, modulation of material chiroptical properties and supramolecular assembly. However, the lack of general design principles, along with the challenging synthesis of these molecules, precludes full exploitation of their dynamic structures. Therefore, systematic investigations of the key parameters are crucial for the further development of these systems. Here we provide a facile alternative synthetic route, elucidate the influence of substituents on the photochemistry of overcrowded alkene-derived bistable chiroptical photoswitches, and show nearly quantitative bidirectional photoswitching. The established structure-property relationship constitutes a practical guideline for the design of these photochromes tailored to a specific application.
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| 15. |
- Stindt, Charlotte N., et al.
(författare)
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Activating a light-driven molecular motor by metal complexation
- 2023
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Ingår i: Chem. - : CELL PRESS. - 2451-9308 .- 2451-9294. ; 9:8
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Tidskriftsartikel (refereegranskat)abstract
- Designing increasingly complex, responsive, and dynamic molecular systems, whose actions can be controlled by a combination of cooperative stimuli, is a key challenge toward the development of more advanced functional molecular machines. Herein, we report new photochemically driven molecular motors based on a bis(benzoxazole) ligand. Coordination of the ligand to a metal salt leads to the selective in situ activation of a well-defined motor function, which can be deactivated in the presence of a competing ligand. The rotation speed and absorption wavelength are tuned by the choice of metal, allowing unprecedented control of the molecular system. DFT calculations show that the geometry of the metal center influences the rotational barriers and the possibility to couple the rotary motion with the wagging movement at the metal center. The approach presented here will open new avenues toward more complex, dynamic, and coupled systems.
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| 16. |
- Toyoda, Ryojun, et al.
(författare)
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Synergistic interplay between photoisomerization and photoluminescence in a light-driven rotary molecular motor
- 2022
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Photoactuators and photoluminescent dyes utilize light to perform mechanical motion and undergo spontaneous radiation emission, respectively. Combining these two functionalities in a single molecule would benefit the construction of advanced molecular machines. Due to the possible detrimental interaction between the two light-dependent functional parts, the design of hybrid systems featuring both functions in parallel remains highly challenging. Here, we develop a light-driven rotary molecular motor with an efficient photoluminescent dye chemically attached to the motor, not compromising its motor function. This molecular system shows efficient rotary motion and bright photoluminescence, and these functions can be addressed by a proper choice of excitation wavelengths and solvents. The moderate interaction between the two parts generates synergistic effects, which are beneficial for lower-energy excitation and chirality transfer from the motor to the photoluminescent dye. Our results provide prospects towards photoactive multifunctional systems capable of carrying out molecular rotary motion and tracking its location in a complex environment.
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| 17. |
- Xu, Fan, et al.
(författare)
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Mechanistic Insight into Supramolecular Polymerization in Water Tunable by Molecular Geometry
- 2022
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Ingår i: CCS Chemistry. - : Chinese Chemical Society. - 2096-5745. ; 4:7, s. 2212-2220
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Tidskriftsartikel (refereegranskat)abstract
- Supramolecular self-assembly in water based on non-covalent bonding is attracting major attention due to the potential of hydrogels and aqueous polymers in biomedical applications. Although supramolecular polymerization in organic solvents is well established, the key design features, the assembly mechanisms in water and achieving control over the aggregate structures remain challenging. Here, we present the assembly and disassembly of geometrical isomers of a stiff-stilbene bis-urea amphiphile (SA) in pure water. A remarkable feature of this system is that the (E)-isomer forms supramolecular polymers in both pure water and organic solvents. Taking advantage of this unique property, the hydrophobic effect was studied by comparing the supramolecular assembly in both systems. The assembly process in water follows an enthalpy-driven nucleation-elongation (cooperative) supramolecular polymerization mechanism with a standard Gibbs free energy (Delta G degrees = -53 kJ mol(-1)) double the value of the one found in toluene. We attributed this distinctive feature to the hydrophobic effect in water. Furthermore, we discovered an isomer-dependent assembly process, which can be used to control aggregation in aqueous media. Due to the substantial geometric difference between (E)-SA and (Z)-SA, we compared their assembly in water to study the influence of different driving forces involved in the process. The supramolecular polymerization of (E)-SA was cooperatively influenced by hydrogen bonding, pi-stacking, and hydrophobic effects, whereas the assembly of (Z)-SA was mainly driven by hydrophobic effects. As a result, the fiber length of (E)-SA in water is much longer than that of (Z)-SA, presenting opportunities for geometrical control of aggregation in aqueous media. [GRAPHICS]
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| 18. |
- Yang, Shun, et al.
(författare)
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Reversibly modulating a conformation-adaptive fluorophore in [2]catenane
- 2021
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Ingår i: Chem. - : Elsevier BV. - 2451-9308 .- 2451-9294. ; 7:6, s. 1544-1556
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Tidskriftsartikel (refereegranskat)abstract
- Tuning molecular emission by chemicalmeans has long been a fundamental topic, because the emerging methodologies and mechanisms of this topic usually bring a lot of opportunities in many multi-disciplinary applications. Here, we demonstrate the reversible switching of a conformation-adaptive fluorophore, 9,14-diphenyl-9,14-dihydrodibenzo[ a,c]phenazine (DPAC), by incorporating this fluorescent unit into a mechanically interlocked [2]catenane. Taking advantage of the mechanical bond of [2]catenane, the conformational freedom of the DPAC-macrocycle can be modulated by the co-conformational state of the [2]catenane, thus enabling the reversible switching of the fluorescent properties of DPAC. Owing to the mechanically interlocked structure, this fluorescent molecular system can be switched in a dual-mode (wavelength or intensity), visually recognizable, and highly reversible manner. This work provides a distinctmechanism of switchingmolecular emission by modulating conformation-adaptive fluorescent systems in mechanically interlocked structures.
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