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1.
Int J Mol Sci ; 24(23)2023 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-38069142

RESUMO

Legume plants have the ability to establish a symbiotic relationship with soil bacteria known as rhizobia. The legume-rhizobium symbiosis results in the formation of symbiotic root nodules, where rhizobia fix atmospheric nitrogen. A host plant controls the number of symbiotic nodules to meet its nitrogen demands. CLE (CLAVATA3/EMBRYO SURROUNDING REGION) peptides produced in the root in response to rhizobial inoculation and/or nitrate have been shown to control the number of symbiotic nodules. Previously, the MtCLE35 gene was found to be upregulated by rhizobia and nitrate treatment in Medicago truncatula, which systemically inhibited nodulation when overexpressed. In this study, we obtained several knock-out lines in which the MtCLE35 gene was mutated using the CRISPR/Cas9-mediated system. M. truncatula lines with the MtCLE35 gene knocked out produced increased numbers of nodules in the presence of nitrate in comparison to wild-type plants. Moreover, in the presence of nitrate, the expression levels of two other nodulation-related MtCLE genes, MtCLE12 and MtCLE13, were reduced in rhizobia-inoculated roots, whereas no significant difference in MtCLE35 gene expression was observed between nitrate-treated and rhizobia-inoculated control roots. Together, these findings suggest the key role of MtCLE35 in the number of nodule numbers under high-nitrate conditions, under which the expression levels of other nodulation-related MtCLE genes are reduced.


Assuntos
Medicago truncatula , Rhizobium , Nodulação/genética , Nódulos Radiculares de Plantas/metabolismo , Nitratos/metabolismo , Simbiose/genética , Sistemas CRISPR-Cas/genética , Medicago truncatula/metabolismo , Nitrogênio/metabolismo , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Rhizobium/metabolismo , Raízes de Plantas/metabolismo
2.
Int J Mol Sci ; 23(23)2022 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-36499210

RESUMO

The C-TERMINALLY ENCODED PEPTIDE(CEP) peptides play crucial roles in plant growth and response to environmental factors. These peptides were characterized as positive regulators of symbiotic nodule development in legume plants. However, little is known about the CEP peptide family in pea. Here, we discovered in pea genome 21 CEP genes (PsCEPs), among which three genes contained additional conserved motifs corresponding to the PIP (PAMP-induced secreted peptides) consensus sequences. We characterized the expression patterns of pea PsCEP genes based on transcriptomic data, and for six PsCEP genes with high expression levels in the root and symbiotic nodules the detailed expression analysis at different stages of symbiosis and in response to nitrate treatment was performed. We suggest that at least three PsCEP genes, PsCEP1, PsCEP7 and PsCEP2, could play a role in symbiotic nodule development, whereas the PsCEP1 and PsCEP13 genes, downregulated by nitrate addition, could be involved in regulation of nitrate-dependent processes in pea. Further functional studies are required to elucidate the functions of these PsCEP genes.


Assuntos
Nódulos Radiculares de Plantas , Nódulos Radiculares de Plantas/metabolismo , Fixação de Nitrogênio/genética , Nitratos/metabolismo , Simbiose/genética , Peptídeos/genética , Peptídeos/metabolismo , Raízes de Plantas/metabolismo , Regulação da Expressão Gênica de Plantas
3.
J Phys Chem Lett ; 13(6): 1578-1586, 2022 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-35138106

RESUMO

The development of patterning materials ("resists") at the nanoscale involves two distinct trends: one is toward high sensitivity and resolution for miniaturization, the other aims at functionalization of the resists to realize bottom-up construction of distinct nanoarchitectures. Patterning of carbon nanostructures, a seemingly ideal application for organic functional resists, has been highly reliant on complicated pattern transfer processes because of a lack of patternable precursors. Herein, we present a fullerene-metal coordination complex as a fabrication material for direct functional patterning of sub-10 nm metal-containing carbon structures. The attachment of one platinum atom per fullerene molecule not only leads to significant improvement of sensitivity and resolution but also enables stable atomic dispersion of the platinum ions within the carbon matrix, which may gain fundamentally new interest in functional patterning of hierarchical carbon nanostructures.

4.
ACS Nano ; 14(9): 11160-11168, 2020 09 22.
Artigo em Inglês | MEDLINE | ID: mdl-32790332

RESUMO

Studying dynamic self-assembling systems in their native environment is essential for understanding the mechanisms of self-assembly and thereby exerting full control over these processes. Traditional ensemble-based analysis methods often struggle to reveal critical features of the self-assembly that occur at the single particle level. Here, we describe a label-free single-particle assay to visualize real-time self-assembly in aqueous solutions by interferometric scattering microscopy. We demonstrate how the assay can be applied to biphasic reactions yielding micellar or vesicular aggregates, detecting the onset of aggregate formation, quantifying the kinetics at the single particle level, and distinguishing sigmoidal and exponential growth of aggregate populations. Furthermore, we can follow the evolution in aggregate size in real time, visualizing the nucleation stages of the self-assembly processes and record phenomena such as incorporation of oily components into the micelle or vesicle lumen.


Assuntos
Interferometria , Microscopia , Cinética , Micelas , Água
5.
Angew Chem Int Ed Engl ; 59(46): 20361-20366, 2020 11 09.
Artigo em Inglês | MEDLINE | ID: mdl-32706135

RESUMO

We report chemically fuelled out-of-equilibrium self-replicating vesicles based on surfactant formation. We studied the vesicles' autocatalytic formation using UPLC to determine monomer concentration and interferometric scattering microscopy at the nanoparticle level. Unlike related reports of chemically fuelled self-replicating micelles, our vesicular system was too stable to surfactant degradation to be maintained out of equilibrium. The introduction of a catalyst, which introduces a second catalytic cycle into the metabolic network, was used to close the first cycle. This shows how coupled catalytic cycles can create a metabolic network that allows the creation and perseverance of fuel-driven, out-of-equilibrium self-replicating vesicles.

6.
PLoS One ; 15(4): e0232352, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32353031

RESUMO

Cytokinin is an important regulator of symbiotic nodule development. Recently, KNOTTED1-LIKE HOMEOBOX 3 transcription factor (TF) was shown to regulate symbiotic nodule development possibly via the activation of cytokinin biosynthesis genes. However, the direct interaction between the KNOX3 TF and its target genes has not been investigated up to date. Here, using EMSA analysis and SPR-based assay, we found that MtKNOX3 homeodomain directly binds to the regulatory sequences of the MtLOG1, MtLOG2, and MtIPT3 genes involved in nodulation in Medicago truncatula. Moreover, we showed that MtLOG2 and MtIPT3 expression patterns partially overlap with MtKNOX3 expression in developing nodules as it was shown by promoter:GUS analysis. Our data suggest that MtKNOX3 TF may directly activate the MtLOG1, MtLOG2, and MtIPT3 genes during nodulation thereby increasing cytokinin biosynthesis in developing nodules.


Assuntos
Citocininas/biossíntese , Regulação da Expressão Gênica de Plantas , Proteínas de Homeodomínio/metabolismo , Medicago truncatula/genética , Proteínas de Plantas/metabolismo , Fatores de Transcrição/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Homeodomínio/genética , Medicago truncatula/crescimento & desenvolvimento , Proteínas de Plantas/genética , Regiões Promotoras Genéticas , Fatores de Transcrição/genética
7.
Planta ; 251(4): 82, 2020 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-32189080

RESUMO

MAIN CONCLUSION: The review provides information on the mechanisms underlying the development of spontaneous and pathogen-induced tumors in higher plants. The activation of meristem-specific regulators in plant tumors of various origins suggests the meristem-like nature of abnormal plant hyperplasia. Plant tumor formation has more than a century of research history. The study of this phenomenon has led to a number of important discoveries, including the development of the Agrobacterium-mediated transformation technique and the discovery of horizontal gene transfer from bacteria to plants. There are two main groups of plant tumors: pathogen-induced tumors (e.g., tumors induced by bacteria, viruses, fungi, insects, etc.), and spontaneous ones, which are formed in the absence of any pathogen in plants with certain genotypes (e.g., interspecific hybrids, inbred lines, and mutants). The causes of the transition of plant cells to tumor growth are different from those in animals, and they include the disturbance of phytohormonal balance and the acquisition of meristematic characteristics by differentiated cells. The aim of this review is to discuss the mechanisms underlying the development of most known examples of plant tumors.


Assuntos
Tumores de Planta/microbiologia , Animais , Bactérias/metabolismo , Fungos/metabolismo , Interações Hospedeiro-Patógeno , Insetos/metabolismo , Meristema/crescimento & desenvolvimento , Meristema/microbiologia , Células Vegetais/metabolismo , Desenvolvimento Vegetal , Reguladores de Crescimento de Plantas/metabolismo , Vírus/metabolismo
8.
J Am Chem Soc ; 142(1): 349-364, 2020 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-31778308

RESUMO

The powerful electron accepting ability of fullerenes makes them ubiquitous components in biomimetic donor-acceptor systems that model the intermolecular electron transfer processes of Nature's photosynthetic center. Exploiting perylene diimides (PDIs) as components in cyclic host systems for the noncovalent recognition of fullerenes is unprecedented, in part because archetypal PDIs are also electron deficient, making dyad assembly formation electronically unfavorable. To address this, we report the strategic design and synthesis of a novel large, macrocyclic receptor composed of two covalently strapped electron-rich bis-pyrrolidine PDI panels, nicknamed the "Green Box" due to its color. Through the principle of electronic complementarity, the Green Box exhibits strong recognition of pristine fullerenes (C60/70), with the noncovalent ground and excited state interactions that occur upon fullerene guest encapsulation characterized by a range of techniques including electronic absorption, fluorescence emission, NMR and time-resolved EPR spectroscopies, cyclic voltammetry, mass spectrometry, and DFT calculations. While relatively low polarity solvents result in partial charge transfer in the host donor-guest acceptor complex, increasing the polarity of the solvent medium facilitates rare, thermally allowed full electron transfer from the Green Box to fullerene in the ground state. The ensuing charge separated radical ion paired complex is spectroscopically characterized, with thermodynamic reversibility and kinetic stability also demonstrated. Importantly, the Green Box represents a seminal type of C60/70 host where electron-rich PDI motifs are utilized as recognition motifs for fullerenes, facilitating novel intermolecular, solvent tunable ground state electronic communication with these guests. The ability to switch between extremes of the charge transfer energy continuum is without precedent in synthetic fullerene-based dyads.

9.
Front Plant Sci ; 9: 304, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29593763

RESUMO

Cytokinins are essential for legume plants to establish a nitrogen-fixing symbiosis with rhizobia. Recently, the expression level of cytokinin biosynthesis IPTs (ISOPENTENYLTRANSFERASES) genes was shown to be increased in response to rhizobial inoculation in Lotus japonicus, Medicago truncatula and Pisum sativum. In addition to its well-established positive role in nodule primordium initiation in root cortex, cytokinin negatively regulates infection processes in the epidermis. Moreover, it was reported that shoot-derived cytokinin inhibits the subsequent nodule formation through AON (autoregulation of nodulation) pathway. In L. japonicus, LjIPT3 gene was shown to be activated in the shoot phloem via the components of AON system, negatively affecting nodulation. However, in M. truncatula, the detailed analysis of MtIPTs expression, both in roots and shoots, in response to nodulation has not been performed yet, and the link between IPTs and AON has not been studied so far. In this study, we performed an extensive analysis of MtIPTs expression levels in different organs, focusing on the possible role of MtIPTs in nodule development. MtIPTs expression dynamics in inoculated roots suggest that besides its early established role in the nodule primordia development, cytokinin may be also important for later stages of nodulation. According to expression analysis, MtIPT3, MtIPT4, and MtIPT5 are activated in the shoots in response to inoculation. Among these genes, MtIPT3 is the only one the induction of which was not observed in leaves of the sunn-3 mutant defective in CLV1-like kinase, the key component of AON, suggesting that MtIPT3 is activated in the shoots in an AON-dependent manner. Taken together, our findings suggest that MtIPTs are involved in the nodule development at different stages, both locally in inoculated roots and systemically in shoots, where their expression can be activated in an AON-dependent manner.

10.
J Am Chem Soc ; 140(5): 1924-1936, 2018 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-29337535

RESUMO

By addressing the challenge of controlling molecular motion, mechanically interlocked molecular machines are primed for a variety of applications in the field of nanotechnology. Specifically, the designed manipulation of communication pathways between electron donor and acceptor moieties that are strategically integrated into dynamic photoactive rotaxanes and catenanes may lead to efficient artificial photosynthetic devices. In this pursuit, a novel [3]rotaxane molecular shuttle consisting of a four-station bis-naphthalene diimide (NDI) and central C60 fullerene bis-triazolium axle component and two mechanically bonded ferrocenyl-functionalized isophthalamide anion binding site-containing macrocycles is constructed using an anion template synthetic methodology. Dynamic coconformational anion recognition-mediated shuttling, which alters the relative positions of the electron donor and acceptor motifs of the [3]rotaxane's macrocycle and axle components, is demonstrated initially by 1H NMR spectroscopy. Detailed steady-state and time-resolved UV-vis-IR absorption and emission spectroscopies as well as electrochemical studies are employed to further probe the anion-dependent positional macrocycle-axle station state of the molecular shuttle, revealing a striking on/off switchable emission response induced by anion binding. Specifically, the [3]rotaxane chloride coconformation, where the ferrocenyl-functionalized macrocycles reside at the center of the axle component, precludes electron transfer to NDI, resulting in the switching-on of emission from the NDI fluorophore and concomitant formation of a C60 fullerene-based charge-separated state. By stark contrast, in the absence of chloride as the hexafluorophosphate salt, the ferrocenyl-functionalized macrocycles shuttle to the peripheral NDI axle stations, quenching the NDI emission via formation of a NDI-containing charge-separated state. Such anion-mediated control of the photophysical behavior of a rotaxane through molecular motion is unprecedented.

11.
J Am Chem Soc ; 140(1): 401-405, 2018 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-29232117

RESUMO

Redox flow batteries have the potential to revolutionize our use of intermittent sustainable energy sources such as solar and wind power by storing the energy in liquid electrolytes. Our concept study utilizes a novel electrolyte system, exploiting derivatized fullerenes as both anolyte and catholyte species in a series of battery cells, including a symmetric, single species system which alleviates the common problem of membrane crossover. The prototype multielectron system, utilizing molecular based charge carriers, made from inexpensive, abundant, and sustainable materials, principally, C and Fe, demonstrates remarkable current and energy densities and promising long-term cycling stability.

12.
J Am Chem Soc ; 140(2): 710-718, 2018 01 17.
Artigo em Inglês | MEDLINE | ID: mdl-29260871

RESUMO

We have employed the scanning tunneling microscope break-junction technique to investigate the single-molecule conductance of a family of 5,15-diaryl porphyrins bearing thioacetyl (SAc) or methylsulfide (SMe) binding groups at the ortho position of the phenyl rings (S2 compounds). These ortho substituents lead to two atropisomers, cis and trans, for each compound, which do not interconvert in solution under ambient conditions; even at high temperatures, isomerization takes several hours (half-life 15 h at 140 °C for SAc in C2Cl4D2). All the S2 compounds exhibit two conductance groups, and comparison with a monothiolated (S1) compound shows the higher group arises from a direct Au-porphyrin interaction. The lower conductance group is associated with the S-to-S pathway. When the binding group is SMe, the difference in junction length distribution reflects the difference in S-S distance (0.3 nm) between the two isomers. In the case of SAc, there are no significant differences between the plateau length distributions of the two isomers, and both show maximal stretching distances well exceeding their calculated junction lengths. Contact deformation accounts for part of the extra length, but the results indicate that cis-to-trans conversion takes place in the junction for the cis isomer. The barrier to atropisomerization is lower than the strength of the thiolate Au-S and Au-Au bonds, but higher than that of the Au-SMe bond, which explains why the strain in the junction only induces isomerization in the SAc compound.

13.
ACS Nano ; 11(3): 2509-2520, 2017 03 28.
Artigo em Inglês | MEDLINE | ID: mdl-28191929

RESUMO

We report an approach, named chemTEM, to follow chemical transformations at the single-molecule level with the electron beam of a transmission electron microscope (TEM) applied as both a tunable source of energy and a sub-angstrom imaging probe. Deposited on graphene, disk-shaped perchlorocoronene molecules are precluded from intermolecular interactions. This allows monomolecular transformations to be studied at the single-molecule level in real time and reveals chlorine elimination and reactive aryne formation as a key initial stage of multistep reactions initiated by the 80 keV e-beam. Under the same conditions, perchlorocoronene confined within a nanotube cavity, where the molecules are situated in very close proximity to each other, enables imaging of intermolecular reactions, starting with the Diels-Alder cycloaddition of a generated aryne, followed by rearrangement of the angular adduct to a planar polyaromatic structure and the formation of a perchlorinated zigzag nanoribbon of graphene as the final product. ChemTEM enables the entire process of polycondensation, including the formation of metastable intermediates, to be captured in a one-shot "movie". A molecule with a similar size and shape but with a different chemical composition, octathio[8]circulene, under the same conditions undergoes another type of polycondensation via thiyl biradical generation and subsequent reaction leading to polythiophene nanoribbons with irregular edges incorporating bridging sulfur atoms. Graphene or carbon nanotubes supporting the individual molecules during chemTEM studies ensure that the elastic interactions of the molecules with the e-beam are the dominant forces that initiate and drive the reactions we image. Our ab initio DFT calculations explicitly incorporating the e-beam in the theoretical model correlate with the chemTEM observations and give a mechanism for direct control not only of the type of the reaction but also of the reaction rate. Selection of the appropriate e-beam energy and control of the dose rate in chemTEM enabled imaging of reactions on a time frame commensurate with TEM image capture rates, revealing atomistic mechanisms of previously unknown processes.

14.
Chemistry ; 22(38): 13540-9, 2016 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-27466153

RESUMO

Electron-transfer processes play a significant role in host-guest interactions and determine physicochemical phenomena emerging at the nanoscale that can be harnessed in electronic or optical devices, as well as biochemical and catalytic systems. A novel method for qualifying and quantifying the electronic doping of single walled carbon nanotubes (SWNTs) using electrochemistry has been developed that establishes a direct link between these experimental measurements and ab initio DFT calculations. Metallocenes such as cobaltocene and methylated ferrocene derivatives were encapsulated inside SWNTs (1.4 nm diameter) and cyclic voltammetry (CV) was performed on the resultant host-guest systems. The electron transfer between the guest molecules and the host SWNTs is measured as a function of shift in the redox potential (E1/2 ) of Co(II) /Co(I) , Co(III) /Co(II) and Fe(III) /Fe(II) . Furthermore, the shift in E1/2 is inversely proportional to the nanotube diameter. To quantify the amount of electron transfer from the guest molecules to the SWNTs, a novel method using coulometry was developed, allowing the mapping of the density of states and the Fermi level of the SWNTs. Correlated with theoretical calculations, coulometry provides an accurate indication of n/p-doping of the SWNTs.

15.
Nanoscale ; 8(22): 11727-37, 2016 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-27222094

RESUMO

A series of explorative cross-coupling reactions have been developed to investigate the local nanoscale environment around catalytically active Pd(ii)complexes encapsulated within hollow graphitised nanofibers (GNF). Two new fullerene-containing and fullerene-free Pd(ii)Salen catalysts have been synthesised, and their activity and selectivity towards different substrates has been explored in nanoreactors. The catalysts not only show a significant increase in activity and stability upon heterogenisation at the graphitic step-edges inside the GNF channel, but also exhibit a change in selectivity affected by the confinement which alters the distribution of isomeric products of the reaction. Furthermore, the observed selectivity changes reveal unprecedented details regarding the location and orientation of the catalyst molecules inside the GNF nanoreactor, inaccessible by any spectroscopic or microscopic techniques, thus shedding light on the precise reaction environment inside the molecular catalyst-GNF nanoreactor.

16.
BMC Plant Biol ; 16 Suppl 1: 7, 2016 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-26821718

RESUMO

BACKGROUND: Radish (Raphanus sativus L.) is a widespread agricultural plant forming storage root due to extensive secondary growth which involves cambium proliferation and differentiation of secondary conductive tissues. Closely related to the model object Arabidopsis thaliana, radish is a suitable model for studying processes of secondary growth and storage root development. CLE peptides are a group of peptide phytohormones which play important role in the regulation of primary meristems such as SAM, RAM, and procambium, as well as secondary meristems. However, the role of CLE peptides in lateral growth of root during storage root formation has not been studied to date. RESULTS: In present work we studied the role of CLE peptides in the development of storage root in radish. We have identified 18 CLE genes of radish (RsCLEs) and measured their expression in various plant organs and also at different stages of root development in R. sativus and Raphanus raphanistrum-its close relative which does not form storage root. We observed significant decline of expression levels for genes RsCLE1, 2, 11, 13, and 16, and also multifold increase of expression levels for genes RsCLE19, and 41 during secondary root growth in R. sativus but not in R. raphanistrum. Expression of RsCLE 2, 19, and 41 in R. sativus root was confined to certain types of tissues while RsCLE1, 11, 13, and 16 expressed throughout the root. Experiments on overexpression of RsCLE2, 19 and 41 or treatment of radish plants with synthetic CLE peptides revealed that CLE19 and CLE2 increase the number of xylem elements, and CLE41 induces the formation of extra cambium foci in secondary xylem. Expression levels of RsCLE2 and 19 strongly decrease in response to exogenous cytokinin, while auxin causes dramatic increase of RsCLE19 expression level and decrease of RsCLE41 expression. CONCLUSIONS: Our data allow us to hypothesize about the role of RsCLE2, 19 and 41 genes in the development of storage root of Raphanus sativus, e.g. RsCLE19 may play a role in auxin-dependent processes of xylem differentiation and RsCLE41 stimulates cambium activity.


Assuntos
Genes de Plantas , Reguladores de Crescimento de Plantas/genética , Raphanus/genética , Citocininas/farmacologia , Expressão Gênica , Ácidos Indolacéticos/farmacologia , Proteínas de Plantas/genética , Proteínas de Plantas/fisiologia , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Raphanus/crescimento & desenvolvimento
17.
Chem Sci ; 7(9): 5908-5921, 2016 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-30034733

RESUMO

Photoreduction of fullerene and the consequent stabilisation of a charge-separated state in a donor-acceptor assembly have been achieved, overcoming the common problem of a fullerene-based triplet state being an energy sink that prevents charge-separation. A route to incorporate a C60-fullerene electron acceptor moiety into a catecholate-Pt(ii)-diimine photoactive dyad, which contains an unusually strong electron donor, 3,5-di-tert-butylcatecholate, has been developed. The synthetic methodology is based on the formation of the aldehyde functionalised bipyridine-Pt(ii)-3,5-di-tert-butylcatechol dyad which is then added to the fullerene cage via a Prato cycloaddition reaction. The resultant product is the first example of a fullerene-diimine-Pt-catecholate donor-acceptor triad, C60bpy-Pt-cat. The triad exhibits an intense solvatochromic absorption band in the visible region due to catechol-to-diimine charge-transfer, which, together with fullerene-based transitions, provides efficient and tuneable light harvesting of the majority of the UV/visible spectral range. Cyclic voltammetry, EPR and UV/vis/IR spectroelectrochemistry reveal redox behaviour with a wealth of reversible reduction and oxidation processes forming multiply charged species and storing multiple redox equivalents. Ultrafast transient absorption and time resolved infrared spectroscopy, supported by molecular modelling, reveal the formation of a charge-separated state [C60˙-bpy-Pt-cat˙+] with a lifetime of ∼890 ps. The formation of cat˙+ in the excited state is evidenced directly by characteristic absorption bands in the 400-500 nm region, while the formation of C60˙- was confirmed directly by time-resolved infrared spectroscopy, TRIR. An IR-spectroelectrochemical study of the mono-reduced building block (C60-bpy)PtCl2, revealed a characteristic C60˙- vibrational feature at 1530 cm-1, which was also detected in the TRIR spectra. This combination of experiments offers the first direct IR-identification of C60˙- species in solution, and paves the way towards the application of transient infrared spectroscopy to the study of light-induced charge-separation in C60-containing assemblies, as well as fullerene films and fullerene/polymer blends in various OPV devices. Identification of the unique vibrational signature of a C60-anion provides a new way to follow photoinduced processes in fullerene-containing assemblies by means of time-resolved vibrational spectroscopy, as demonstrated for the fullerene-transition metal chromophore assembly with the lowest energy charge-separated excited state.

19.
Beilstein J Org Chem ; 10: 332-43, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24605154

RESUMO

A series of six fullerene-linker-fullerene triads have been prepared by the stepwise addition of the fullerene cages to bridging moieties thus allowing the systematic variation of fullerene cage (C60 or C70) and linker (oxalate, acetate or terephthalate) and enabling precise control over the inter-fullerene separation. The fullerene triads exhibit good solubility in common organic solvents, have linear geometries and are diastereomerically pure. Cyclic voltammetric measurements demonstrate the excellent electron accepting capacity of all triads, with up to 6 electrons taken up per molecule in the potential range between -2.3 and 0.2 V (vs Fc(+)/Fc). No significant electronic interactions between fullerene cages are observed in the ground state indicating that the individual properties of each C60 or C70 cage are retained within the triads. The electron-electron interactions in the electrochemically generated dianions of these triads, with one electron per fullerene cage were studied by EPR spectroscopy. The nature of electron-electron coupling observed at 77 K can be described as an equilibrium between doublet and triplet state biradicals which depends on the inter-fullerene spacing. The shorter oxalate-bridged triads exhibit stronger spin-spin coupling with triplet character, while in the longer terephthalate-bridged triads the intramolecular spin-spin coupling is significantly reduced.

20.
Chemistry ; 19(36): 11999-2008, 2013 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-23881673

RESUMO

A covalently-linked salen-C60 (H2L) assembly binds a range of transition metal cations in close proximity to the fullerene cage to give complexes [M(L)] (M=Mn, Co, Ni, Cu, Zn, Pd), [MCl(L)] (M=Cr, Fe) and [V(O)L]. Attaching salen covalently to the C60 cage only marginally slows down metal binding at the salen functionality compared to metal binding to free salen. Coordination of metal cations to salen-C60 introduces to these fullerene derivatives strong absorption bands across the visible spectrum from 400 to 630 nm, the optical features of which are controlled by the nature of the transition metal. The redox properties of the metal-salen-C60 complexes are determined both by the fullerene and by the nature of the transition metal, enabling the generation of a wide range of fullerene-containing charged species, some of which possess two or more unpaired electrons. The presence of the fullerene cage enhances the affinity of these complexes for carbon nanostructures, such as single-, double- and multiwalled carbon nanotubes and graphitised carbon nanofibres, without detrimental effects on the catalytic activity of the metal centre, as demonstrated in styrene oxidation catalysed by [Cu(L)]. This approach shows promise for applications of salen-C60 complexes in heterogeneous catalysis.

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