- Turn-off mode fluorescent norbornadiene-based photoswitches
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Single-molecule fluorescence emission of certain positive photochromic systems such as diarylethenes have been exploited for biological imaging and optical memory storage applications. However, there is a lack of understanding if negative photochromic sys
- Tebikachew, Behabitu Ergette,Edhborg, Fredrik,Kann, Nina,Albinsson, Bo,Moth-Poulsen, Kasper
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p. 23195 - 23201
(2018/09/29)
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- Donor–acceptor–acceptor-based non-fullerene acceptors comprising terminal chromen-2-one functionality for efficient bulk-heterojunction devices
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Two simple semiconducting donor–acceptor–acceptor (D–A1–A) modular, small molecule, non-fullerene electron acceptors, 2-(4-(diphenylamino)phenyl)-3-(4-((2-oxo-2H-chromen-3-yl)ethynyl)phenyl)buta-1,3-diene-1,1,4,4-tetracarbonitrile (P2) and 2-(4-(3,3-dicyano-1-(4-(diphenylamino)phenyl)-2-(4-((2-oxo-2H-chromen-3-yl)ethynyl)phenyl)allylidene)cyclohexa-2,5-dien-1-ylidene)malononitrile (P3), were designed, synthesized and characterized for application in solution-processable bulk-heterojunction solar cells. The optoelectronic and photovoltaic properties of P2 and P3 were directly compared with those of a structural analogue, 3-((4-((4-(diphenylamino)phenyl)ethynyl)phenyl)ethynyl)-2H-chromen-2-one (P1), which was designed based on a D–A format. All of these new materials comprised an electron rich triphenylamine (TPA) donor core (D) and electron deficient chromen-2-one terminal core (A). In the simple D–A system, TPA and chromenone were the terminal functionalities, whereas in the D–A1–A system, tetracyanoethylene (TCNE) and tetracyanoquinodimethane (TCNQ) derived functionalities were incorporated as A1 units by keeping the D/A units constant. The inclusion of A1 was primarily done to induce cross-conjugation within the molecular backbone and hence to generate low band gap targets. The physical and optoelectronic properties were characterized by ultraviolet–visible (UV–Vis), thermogravimetric analysis, photo-electron spectroscopy in air and cyclic voltammetry. These new materials exhibited broadened absorption spectra, for instance panchromatic absorbance in case of P3, excellent solubility and thermal stability, and energy levels matching those of the conventional and routinely used donor polymer poly(3-hexyl thiophene) (P3HT). Solution-processable bulk-heterojunction devices were fabricated with P1, P2 and P3 as non-fullerene electron acceptors. Studies on the photovoltaic properties revealed that the best P3HT: P3-based device showed an impressive enhanced power conversion efficiency of 4.21%, an increase of around two-fold with respect to the efficiency of the best P3HT: P1-based device (2.28%). Our results clearly demonstrate that the D–A1–A type small molecules are promising non-fullerene electron acceptors in the research field of organic solar cells.
- Srinivasa Rao, Pedada,Gupta, Akhil,Bhosale, Sidhanath V.,Bilic, Ante,Xiang, Wanchun,Evans, Richard A.,Bhosale, Sheshanath V.
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p. 502 - 511
(2017/07/28)
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- Magnetic resonance imaging/fluorescence dual modality protocol using designed phosphonate ligands coupled to superparamagnetic iron oxide nanoparticles
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A simple and versatile methodology to tailor the surface of superparamagnetic iron oxide nanoparticles (SPIONs), and render additional fluorescence capability to these contrast agents, is reported. The dual modality imaging protocol was developed by designing multi-functional scaffolds with a combination of orthogonal moieties for aqueous dispersion and stealth, to covalently link them to SPIONs, and carry out post-functionalization of nanoparticles. SPIONs stabilized with ligands incorporating surface-anchoring phosphonate groups, ethylene glycol backbone for aqueous dispersion, and free surface exposed OH moieties were coupled to near-infrared dye Cy5.5A. Our results demonstrate that design of multi-tasking ligands with desired combination and spatial distribution of functions provides an ideal platform to construct highly efficient dual imaging probes with balanced magnetic, optical and cell viability properties.
- Lam, Tina,Avti, Pramod K.,Pouliot, Philippe,Tardif, Jean-Claude,Rhéaume, éric,Lesage, Frederic,Kakkar, Ashok
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p. 3969 - 3981
(2016/06/13)
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- Self-assembly and (hydro)gelation triggered by cooperative π-π And unconventional C-H×××X hydrogen bonding interactions
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Weak C-H×××X hydrogen bonds are important stabilizing forces in crystal engineering and anion recognition in solution. In contrast, their quantitative influence on the stabilization of supramolecular polymers or gels has thus far remained unexplored. Herein, we report an oligophenyleneethynylene (OPE)-based amphiphilic PtII complex that forms supramolecular polymeric structures in aqueous and polar media driven by π-π and different weak C-H×××X (X=Cl, O) interactions involving chlorine atoms attached to the PtII centers as well as oxygen atoms and polarized methylene groups belonging to the peripheral glycol chains. A collection of experimental techniques (UV/Vis, 1D and 2D NMR, DLS, AFM, SEM, and X-Ray diffraction) demonstrate that the interplay between different weak noncovalent interactions leads to the cooperative formation of self-assembled structures of high aspect ratio and gels in which the molecular arrangement is maintained in the crystalline state. Growing hand in hand! Multiple unconventional C-H×××X (X=O, Cl) hydrogen-bonding interactions, assisted by π-π interactions, are strong enough to drive the cooperative formation of supramolecular polymers and gels in polar and aqueous media. The aggregates consolidate themselves in the crystals, as shown by combined studies in solution and crystalline state. Copyright
- Rest, Christina,Mayoral, María José,Fucke, Katharina,Schellheimer, Jennifer,Stepanenko, Vladimir,Fernández, Gustavo
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p. 700 - 705
(2014/01/23)
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- H-aggregates of oligophenyleneethynylene (OPE)-BODIPY systems in water: Guest size-dependent encapsulation mechanism and co-aggregate morphology
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The synthesis of a new oligophenyleneethynylene (OPE)-4,4-difluoro-4-bora- 3a,4a-diaza-s-indacene (BODIPY) bolaamphiphile 1 and its aqueous self-assembly are reported. Compound 1 forms H-type aggregates in aqueous and polar media, as demonstrated by UV/Vis and fluorescence experiments. Concentration-dependent 1H NMR studies in CD3CN reveal that the BODIPY units are arranged on top of each other into π-stacks with H-type excitonic coupling, as supported by ROESY NMR and theoretical calculations and visualized by Cryo-SEM studies. A detailed analysis of the spectral changes observed in temperature-dependent UV/Vis studies reveals that 1 self-assembles in a non-cooperative (isodesmic) fashion in water. The hydrophobic interior of these self-assembled structures can be exploited to encapsulate hydrophobic dyes, such as tetracene and anthracene. Both dyes absorb in a complementary region of the UV/Vis spectrum and are small enough to interact with the hydrophobic segments of 1. Temperature-dependent UV/Vis studies reveal that the spectral changes associated to the encapsulation mechanism of tetracene can be fitted to a Boltzmann function, and the initially flexible fibres of 1 rigidify upon guest addition. In contrast, the co-assembly of 1 and anthracene is a highly cooperative process, which suggests that a different class of (more-ordered) aggregates is formed. TEM and Cryo SEM imaging show the formation of uniform spherical nanoparticles, indicating that a subtle change in the guest molecular structure induces a significant change in the encapsulation mechanism and, consequently, the aggregate morphology. Dye encapsulation: We report the aqueous self-assembly of a new oligophenyleneethynylene (OPE)-BODIPY amphiphilic derivative into H-type aggregates and its ability to encapsulate hydrophobic guest molecules. Subtle changes in the guest size induce a dramatic change of the encapsulation mechanism. Addition of tetracene leads to the non-cooperative formation of stiff fibres, whereas co-assembly with anthracene is a highly cooperative process, leading to highly organized micellar assemblies.
- Allampally, Naveen Kumar,Florian, Alexander,Mayoral, Maria Jose,Rest, Christina,Stepanenko, Vladimir,Fernandez, Gustavo
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p. 10669 - 10678
(2014/11/07)
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- Cooperative supramolecular polymerization driven by metallophilic Pd?Pd interactions
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A new oligophenyleneethynylene (OPE)-based Pd(II) pyridyl complex has been synthesized, and its self-assembly has been investigated in solution, in the bulk state, and on surfaces. Detailed analysis of concentration- and temperature-dependent UV-vis studies in methylcyclohexane supported by DFT calculations demonstrate for the first time that cooperative supramolecular polymerization processes can be driven by metallophilic interactions.
- Mayoral, María José,Rest, Christina,Stepanenko, Vladimir,Schellheimer, Jennifer,Albuquerque, Rodrigo Q.,Fernández, Gustavo
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p. 2148 - 2151
(2013/03/28)
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- Alternated stacks of nonpolar oligo(p-phenyleneethynylene)-BODIPY systems
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Supramolecular chemistry: The self-assembly of an oligo(p- phenyleneethynylene)-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (OPE-BODIPY) system into alternated 1D π stacks in solution exhibited liquid-crystalline properties at room temperature. This system represents a new approach towards a controlled dye organization exclusively driven by π-π interactions (see figure). Copyright
- Florian, Alexander,Mayoral, María José,Stepanenko, Vladimir,Fernández, Gustavo
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p. 14957 - 14961
(2013/01/15)
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- Single-step electron transfer on the nanometer scale: Ultra-fast charge shift in strongly coupled zinc porphyrin-gold porphyrin dyads
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The synthesis, electrochemical properties, and photoinduced electron transfer processes of a series of three novel zinc(II)-gold(III) bisporphyrin dyads (ZnP-S-AuP+) are described. The systems studied consist of two trisaryl porphyrins connected directly in the meso position via an alkyne unit to tert-(phenylenethynylene) or penta(phenylenethynylene) spacers. In these dyads, the estimated center to center interporphyrin separation distance varies from 32 to 45 A. The absorption, emission, and electrochemical data indicate that there are strong electronic interactions between the linked elements, thanks to the direct attachment of the spacer on the porphyrin ring through the alkyne unit. At room temperature in toluene, light excitation of the zinc porphyrin results in almost quantitative formation of the charge shifted state +ZnP-S-AuP, whose lifetime is in the order of hundreds of picoseconds. In this solvent, the charge-separated state decays to the ground state through the intermediate population of the zinc porphyrin triplet excited state. Excitation of the gold porphyrin leads instead to rapid energy transfer to the triplet ZnP. In dichloromethane the charge shift reactions are even faster, with time constants down to 2 ps, and may be induced also by excitation of the gold porphyrin. In this latter solvent, the longest charge-shifted lifetime (τ = 2.3 ns) was obtained with the penta(phenylenethynylene) spacer. The charge shift reactions are discussed in terms of bridge-mediated super-exchange mechanisms as electron or hole transfer. These new bis-porphyrin arrays, with strong electronic coupling, represent interesting molecular systems in which extremely fast and efficient long-range photoinduced charge shift occurs over a long distance. The rate constants are two to three orders of magnitude larger than for corresponding ZnP-AuP+ dyads linked via mesophenyl groups to oligo-phenyleneethynylene spacers. This study demonstrates the critical impact of the attachment position of the spacer on the porphyrin on the electron transfer rate, and this strategy can represent a useful approach to develop molecular photonic devices for long-range charge separations.
- Fortage, Jerome,Boixel, Julien,Blart, Errol,Hammarstroem, Leif,Becker, Hans Christian,Odobel, Fabrice
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scheme or table
p. 3467 - 3480
(2009/04/10)
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- Geometrically homogenous series of covalently linked zinc/free-base porphyrin dimers of varying length; design, synthesis and characterization
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Singlet excitation energy transfer, SEET, can be mediated by a bridge, connecting an energy donor and acceptor, via a superexchange mechanism. The mediation efficiency depends on the energy difference between the first excited states of the donor and the bridge, ΔEDB, as well as the donor-acceptor distance, RDA. We have previously constructed a series of donor-bridge-acceptor, D-B-A, systems that allowed us to study how SEET depends on ΔEDB. To expand this study into a second dimension, the distance dependence, a new series of D-B-A systems were constructed. This series was based on the same zinc/free-base porphyrin couple as the donor-acceptor pair in the previous series. Their relative orientation was also retained. In contrast to our first series, the bridges in the latter were of varying length. The bridges were oligo(phenyleneethynylene)phenylene (OPE) structures and the length was systematically changed by increasing the number of phenyleneethynylene units from 1 to 4. To obtain high quality samples, the D-B-A systems were assembled by a building block approach where the zinc and free-base porphyrins were introduced separately using Heck alkynylations. The performance of the OPE structure as a mediator and scaffold is discussed in terms of singlet excited state energies and flexibility. For the first time, when combining the topical D-B-A systems with our previous subset, a homogeneous series of D-B-A systems has been synthesized that allows for studies of both the distance dependence and the energy difference dependence of SEET. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Ljungdahl, Thomas,Pettersson, Karin,Albinsson, Bo,Martensson, Jerker
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p. 3087 - 3096
(2007/10/03)
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- Convergent synthesis of platinum-acetylide dendrimers
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An efficient convergent route to the main chain type of organometallic dendrimers, in which platinum moieties are linked by 1,3,5-triethynylbenzene, has been developed. The synthesis of platinum-acetylide dendrons involved the use of two types of trialkylsilyl groups for protection of the terminal acetylene. The platinum-acetylide dendrimers were prepared up to the third generation by reacting dendrons with a triplatinum core and a tetraplatinum core. Spectroscopic characterization and trace experiments by gel permeation chromatography indicated that the dendrimer molecules have no structural defects. Although a π-conjugated system was used as the bridging ligand, electronic and fluorescence spectra suggested that the interaction among the platinum-acetylide moieties in the dendrimers was small.
- Onitsuka, Kiyotaka,Fujimoto, Masanori,Kitajima, Hotaka,Ohshiro, Nobuaki,Takei, Fumie,Takahashi, Shigetoshi
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p. 6433 - 6446
(2007/10/03)
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- Synthesis and Characterization of Dendritic Multichromophores Based on Rylene Dyes for Vectorial Transduction of Excitation Energy
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The synthesis of dendritic multichromophores based on a rigid polyphenylene scaffold is presented. Different rylene chromophores are incorporated into the core, the branches, and the surface of the dendrimer. In this way, two generations of dendritic dyads consisting of a terrylenediimide core, a stiff polyphenylene scaffold, and a perylenemonoimide periphery were obtained. Furthermore, the first synthetic approach to a dendritic triad is introduced. The outer sphere of this macromolecule is formed by naphthalenemonoimide chromophores, whereas perylenemonoimide groups are located in the dendritic scaffold, and the terrylenediimide chromophore serves as a core molecule. This multichromophore absorbs over the whole range of the visible spectrum and shows well-separated absorption envelopes. In the course of dendrimer synthesis new attempts towards a straightforward functionalization strategy for rylene dyes are also presented.
- Weil, Tanja,Reuther, Erik,Beer, Cornelia,Muellen, Klaus
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p. 1398 - 1414
(2007/10/03)
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- Preparation of a rigid macrocycle with two exotopic phenanthroline binding sites
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The preparation of the first rigid macrocyclic bisphenan-throline with exotopic binding sites is described using a series of Sonogashira coupling reactions.
- Schmittel, Michael,Ammon, Horst
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p. 750 - 752
(2007/10/03)
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- Sequential catalytic synthesis of rod-like conjugated poly-ynes
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Several poly-ynes X-[C ≡ C-C6H4-](n)C ≡ C-Si(i)Pr3 (X = H, SiMe3) with controlled length (n = 1, 2, 3, 4) have been prepared from the easily accessible 4-trimethylsilylethynyl iodobenzene by using iterative and convergent methods based on both Pd/Cu catalysed C-C cross-coupling and selective desilylation reactions.
- Lavastre, Olivier,Ollivier, Laurence,Dixneuf, Pierre H.,Sibandhit, Sourisak
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p. 5495 - 5504
(2007/10/03)
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