Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 30
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Phys Chem Chem Phys ; 22(22): 12373-12381, 2020 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-32309827

RESUMO

In spite of their remarkable luminescence properties, benzothioxanthene imide (BTXI, an imide containing rylene chromophores) derivatives have been largely overlooked compared to their perylene bisimide and naphthalene bisimide counterparts. Thus, their detailed photophysics are much less understood. In this paper, we show how relatively simple structural modifications of the backbone of BTXIs can lead to impressive variations in their inter-system crossing kinetics. Thus, through rational engineering of their structure, it is possible to obtain a triplet formation quantum yield that reaches unity, making BTXI a promising class of compounds for triplet-based applications (photodynamic therapy, electroluminescence, etc.).

2.
Artigo em Inglês | MEDLINE | ID: mdl-32336084

RESUMO

While magnetic supports have been widely used to immobilize homogeneous catalysts in organic chemistry, this strategy has so far found very little application in photocatalysis. Indeed, magnetic supports are dark colored, and thus compete for photon absorption with photocatalysts themselves. We have developed a series of core-shell Fe(0)-silica nanoparticles as supports for immobilizing the photosensitizer Ru(bpy)32+, featuring various silica shell thicknesses-16-34 nm SiO2-on 9 nm Fe cores. The supports and the resulting photocatalytic systems were studied for their magnetic, optical, and catalytic properties in the context of the photooxidation of citronellol, and we found that thicker silica shells lead to higher catalytic activity. We correlated this effect as well as Ru(bpy)32+ fluorescence and singlet oxygen generation to the absorption properties of the supports. We were able to reuse our optimal system three times with minimal loss of activity and achieved turnover numbers largely surpassing the performance of homogeneous Ru(bpy)32+. This work highlights the role of material design in the conception of new supports for applications in heterogeneous photocatalysis.

3.
Molecules ; 25(5)2020 Mar 03.
Artigo em Inglês | MEDLINE | ID: mdl-32138280

RESUMO

A current trend within photo-dynamic therapy (PDT) is the development of molecular systems targeting hypoxic tumors. Thus, type I PDT sensitizers could here overcome traditional type II molecular systems that rely on the photo-initiated production of toxic singlet oxygen. Here, we investigate the cell localization properties and toxicity of two polymeric anthracene-based fluorescent probes (neutral Ant-PHEA and cationic Ant-PIm). The cell death and DNA damage of Chinese hamster ovary cancer cells (CHO-K1) were characterized as combining PDT, cell survival studies (MTT-assay), and comet assay. Confocal microscopy was utilized on samples incubated together with either DRAQ5, Lyso Tracker Red, or Mito Tracker Deep Red in order to map the localization of the sensitizer into the nucleus and other cell compartments. While Ant-PHEA did not cause significant damage to the cell, Ant-PIm showed increased cell death upon illumination, at the cost of a significant dark toxicity. Both anthracene chromophores localized in cell compartments of the cytosol. Ant-PIm showed a markedly improved selectivity toward lysosomes and mitochondria, two important biological compartments for the cell's survival. None of the two anthracene chromophores showed singlet oxygen formation upon excitation in solvents such as deuterium oxide or methanol. Conclusively, the significant photo-induced cell death that could be observed with Ant-PIm suggests a possible type I PDT mechanism rather than the usual type II mechanism.

4.
Inorg Chem ; 58(12): 7730-7745, 2019 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-31140791

RESUMO

Three new copper(I) complexes [Cu(LX)2]+(PF6-) (where LX stands for 2,9-dihalo-1,10-phenanthroline and X = Cl, Br, and I) have been synthesized in order to study the impact of halogen substituents tethered in the α position of the chelating nitrogen atoms on their physical properties. The photophysical properties of these new complexes (hereafter named Cu-X) were characterized in both their ground and excited states. Femtosecond ultrafast spectroscopy revealed that early photoinduced processes are faster for Cu-I than for Cu-Cl or Cu-Br, both showing similar behaviors. Their electronic absorption and electrochemical properties are comparable to benchmark [Cu(dmp)2]+ (where dmp stands for 2,9-dimethyl-1,10-phenanthroline); furthermore, their optical features were fully reproduced by time-dependent density functional theory and ab initio molecular dynamics calculations. All three complexes are luminescent at room temperature, showing that halogen atoms bound to positions 2 and 9 of phenanthroline are sufficiently bulky to prevent strong interactions between the excited Cu complexes and solvent molecules in the coordination sphere. Their behavior in the excited state, more specifically the extent of the photoluminescence efficiency and its dependence on the temperature, is, however, strongly dependent on the nature of the halogen. A combination of ultrafast transient absorption spectroscopy, temperature-dependent steady-state fluorescence spectroscopy, and computational chemistry allows one to gain a deeper understanding of the behavior of all three complexes in their excited state.

5.
Chemistry ; 25(38): 9026-9034, 2019 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-30972809

RESUMO

Two trispicolinate 1,4,7-triazacyclonane (TACN)-based ligands bearing three picolinate biphotonic antennae were synthetized and their Yb3+ and Gd3+ complexes isolated. One series differs from the other by the absence (L1 )/presence (L2 ) of bromine atoms on the antenna backbone, offering respectively improved optical and singlet-oxygen generation properties. Photophysical properties of the ligands, complexes and micellar Pluronic suspensions were investigated. Complexes exhibit high two-photon absorption cross-section combined either with NIR emission (Yb) or excellent 1 O2 generation (Gd). The very large intersystem crossing efficiency induced by the combination of bromine atom and heavy rare-earth element was corroborated with theoretical calculations. The 1 O2 generation properties of L2 Gd micellar suspension under two-photon activation leads to tumour cell death, suggesting the potential of such structures for theranostic applications.

6.
Chem Commun (Camb) ; 54(71): 9909-9912, 2018 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-30105319

RESUMO

The reactivity of fluoroalkylselenotoluenesulfonates with unsaturated substrates is explored herein. The direct activation of these shelf-stable reagents under visible light allows the double functionalisation of alkenes or alkynes efficiently, leading to a wide range of ß-fluoroalkylselenolated sulfones. Mechanistic investigations have been undertaken supporting the formation of radical intermediates.

7.
Angew Chem Int Ed Engl ; 57(36): 11781-11785, 2018 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-29985549

RESUMO

The first visible-light-mediated synthesis of trifluoromethylselenolated arenes under metal-free conditions is reported. The use of an organic photocatalyst enables the trifluoromethylselenolation of arene diazonium salts using the shelf-stable reagent trifluoromethyl tolueneselenosulfonate at room temperature. The reaction does not require the presence of any additives and shows high functional-group tolerance, covering a very broad range of starting materials. Mechanistic investigations, including EPR spectroscopy, luminescence investigations, and cyclic voltammetry allow rationalization of the reaction mechanism.

8.
J Phys Chem Lett ; 8(23): 5915-5920, 2017 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-29148817

RESUMO

The implication of guanine-rich DNA sequences in biologically important roles such as telomerase dysfunction and the regulation of gene expression has prompted the search for structure-specific G-quadruplex agents for targeted diagnostic and therapeutic applications. Herein, we report on a near-infrared (NIR) two-photon poly(cationic) anthracene-based macromolecule able to selectively target G-quadruplexes (G4s) over genomic double-stranded DNA. In particular, the striking changes in its linear and third-order nonlinear optical properties, combined with the emergence of a strong induced electronic circular dichroism (ECD) signal upon binding to canonical and noncanonical DNA secondary structures allowed for a highly specific detection of several different G4s. Furthermore, through a detailed computational analysis we bring compelling evidence that our probe intercalation within G4s is a thermodynamically favored event, and we fully rationalize the spectroscopic evolution resulting from this complexation event by providing a reasonable explanation regarding the origin of the peculiar ECD effect that accompanies it.


Assuntos
DNA/química , Quadruplex G , Substâncias Macromoleculares , Sequência de Bases , Dicroísmo Circular , Corantes Fluorescentes/química , Guanina/química , Conformação de Ácido Nucleico , Fótons , Termodinâmica
9.
Biomacromolecules ; 18(12): 4022-4033, 2017 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-29020442

RESUMO

One of the challenges of photodynamic therapy is to increase the penetration depth of light irradiation in the tumor tissues. Although two-photon excitation strategies have been developed, the two-photon absorption cross sections of clinically used photosensitizers are generally low (below 300 GM). Besides, photosensitizers with high cross section values are often non-water-soluble. In this research work, a whole family of photosensitizer-polymer conjugates was synthesized via the covalent binding of a photosensitizer with a relatively high cross section along a biocompatible copolymer chain. The resulting photosensitizer-polymer conjugates were water-soluble and could be imaged in cellulo by two-photon microscopy thanks to their high two-photon absorption cross sections (up to 2600 GM in water, in the NIR range). In order to explore the structure/photodynamic activity relationship of such macromolecular photosensitizers, the influence of the polymer size, photosensitizer density, and presence of charges along the polymer backbone was investigated (neutral, anionic, cationic, and zwitterionic conjugates were compared). The macromolecular photosensitizers were not cytotoxic in the absence of light irradiation. Their kinetics of cellular uptake in the B16-F10 melanoma cell line were followed by flow cytometry over 24 h. The efficiency of cell death upon photoactivation was found to be highly correlated to the cellular uptake in turn correlated to the global charge of the macromolecular photosensitizer which appeared as the determining structural parameter.


Assuntos
Morte Celular/efeitos dos fármacos , Neoplasias/tratamento farmacológico , Fármacos Fotossensibilizantes/química , Fármacos Fotossensibilizantes/farmacologia , Polímeros/química , Polímeros/farmacologia , Animais , Linhagem Celular Tumoral , Fluorescência , Substâncias Macromoleculares/farmacologia , Melanoma/tratamento farmacológico , Camundongos , Estrutura Molecular , Tamanho da Partícula , Fotoquimioterapia/métodos , Fótons , Relação Estrutura-Atividade
10.
Chem Commun (Camb) ; 53(41): 5653-5656, 2017 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-28484756

RESUMO

A variety of unprecedented scaffolds containing a difluoroacyl moiety were obtained in moderate to good yields, with excellent diastereoselectivity, via electrochemical or photochemical activation of difluoroacyl heteroaryles with a series of olefinic substrates.

11.
Chem Sci ; 8(1): 381-394, 2017 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-28451183

RESUMO

The synthesis of keto-heptamethine derivatives has been expanded to various new symmetrical and asymmetrical structures, including an unprecedented di-anionic keto-polymethine. The spectroscopic behavior of these new dyes has been systematically and thoroughly investigated, revealing that the formation of hydrogen bond interactions with protic solvents is responsible for a dramatic enhancement of the fluorescence quantum yield in the far-red spectral region. The existence of these strong hydrogen-bond interactions was further confirmed by molecular dynamics simulations. These bis-dipolar polymethines exhibit large two-photon absorption (TPA) cross-sections (σ2 in GM) in the near-infrared, making them ideal candidates for NIR-to-NIR two-photon microscopy imaging applications. We demonstrate that the molecular engineering of the hydrophilic/hydrophobic balance enables targeting of different cellular components, such as cytoplasm or cell membranes. Addition of appropriate substituents provides the molecule with high-water-solubility, affording efficient two-photon probes for angiography.

12.
ACS Omega ; 2(9): 5715-5725, 2017 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-30023750

RESUMO

The binding interaction of a biocompatible water-soluble polycationic two-photon fluorophore (Ant-PIm) toward human serum albumin (HSA) was thoroughly investigated under simulated physiological conditions using a combination of steady-state, time-resolved, and two-photon excited fluorescence techniques. The emission properties of both Ant-PIm and the fluorescent amino acid residues in HSA undergo remarkable changes upon complexation allowing the thermodynamic profile associated with Ant-PIm-HSA complexation to be accurately established. The marked increase in Ant-PIm fluorescence intensity and quantum yield in the proteinous environment seems to be the outcome of the attenuation of radiationless decay pathways resulting from motional restriction imposed on the fluorophore. Fluorescence resonance energy transfer and site-marker competitive experiments provide conclusive evidence that the binding of Ant-PIm preferentially occurs within the subdomain IIA. The pronounced hypsochromic effect and increased fluorescence enhancement upon association with HSA, compared to that of bovine serum albumin (BSA) and other biological interferents, makes the polymeric Ant-PIm probe a valuable sensing agent in rather complex biological environments, allowing facile discrimination between the closely related HSA and BSA. Furthermore, the strong two-photon absorption (TPA) with a maximum located at 820 nm along with a TPA cross section σ2 > 800 GM, and the marked changes in the position and intensity of the band upon complexation definitely make Ant-PIm a promising probe for two-photon excited fluorescence-based discrimination of HSA from BSA.

13.
Soft Matter ; 12(48): 9749-9758, 2016 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-27886321

RESUMO

We demonstrated recently that polyelectrolytes with cationic moieties along the chain and a single anionic head are able to form physical hydrogels due to the reversible nature of the head-to-body ionic bond. Here we generate a variety of such polyelectrolytes with various cationic moieties and counterion combinations starting from a common polymeric platform. We show that the rheological properties (shear modulus, critical strain) of the final hydrogels can be modulated over three orders of magnitude depending on the cation/anion pair. Our data fit remarkably well within a scaling model involving a supramolecular head-to-tail single file between cross-links, akin to the behaviour of pine-processionary caterpillar. This model allows the quantitative measure of the amount of counterion condensation from standard rheology procedure.

14.
Biomacromolecules ; 17(11): 3609-3618, 2016 11 14.
Artigo em Inglês | MEDLINE | ID: mdl-27696875

RESUMO

We report the synthesis, spectroscopy, and the DNA binding properties of a biocompatible, water-soluble, polycationic two-photon absorbing anthracenyl derivative (Ant-PIm) specifically designed for biorelated applications. Detailed insights into the Ant-PIm-DNA binding interaction are provided by using several spectroscopic approaches, including UV-vis absorption, circular dichroism (CD), Fourier-transform infrared spectroscopy (FTIR), steady-state, and time-resolved fluorescence techniques. Absorption and fluorescence quantitative data analysis show a strong Ant-PIm-duplex interaction with binding constants of Kf = 4.7 ± 0.2 × 105 M-1, 7.1 ± 0.3 × 105 M-1, and 1.0 ± 0.1 × 106 M-1 at 298, 304, and 310 K, respectively. Spectral changes observed upon DNA binding provide evidence for a complex formation with off-on fluorescence pattern, which can be related to two consecutive binding equilibria. Results of DNA binders displacement and iodide quenching experimental assays unambiguously point to the groove binding mode of Ant-PIm to the DNA-helicate. Thermodynamic and chemical denaturation studies suggest that long-range interactions of hydrophobic nature regulate the association of Ant-PIm with the biopolymer. The ionic strength dependence of the binding constant shows that electrostatic component has an important contribution to the overall Gibbs free energy. FTIR and CD data provide evidence of partial modification of the B-DNA secondary structure, while the increase in the melting temperature clearly indicates the enhancement of the thermal stability of the duplex. Furthermore, the two-photon absorption cross section spectrum determined using the two-photon excited fluorescence (TPEF) technique shows a strong 2PA maximum at 820 nm with a σ2 > 800 GM, which emphasizes the advantageous combination of biological and optical properties possessed by this positively charged bioprobe.


Assuntos
Antracenos/química , DNA/química , Corantes Fluorescentes/química , Cátions/química , Dicroísmo Circular , Interações Hidrofóbicas e Hidrofílicas , Concentração Osmolar , Espectrometria de Fluorescência , Espectroscopia de Infravermelho com Transformada de Fourier
15.
Inorg Chem ; 55(19): 9586-9595, 2016 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-27618579

RESUMO

A tris-cyclometalated iridium complex that bears two ligands functionalized by peripheral carbazole groups combines an intense solid state emission and a significant two-photon absorption cross section in the near-infrared. After incorporation into a physiological micellar suspension, it can be used for the intravital two-photon fluorescence microscopy of cerebral vasculature.


Assuntos
Carbazóis/química , Complexos de Coordenação/química , Corantes Fluorescentes/química , Irídio/efeitos da radiação , Animais , Encéfalo/irrigação sanguínea , Encéfalo/diagnóstico por imagem , Carbazóis/síntese química , Complexos de Coordenação/síntese química , Fluorescência , Corantes Fluorescentes/síntese química , Raios Infravermelhos , Microscopia Intravital , Irídio/química , Camundongos , Fótons
16.
Chemphyschem ; 17(14): 2128-36, 2016 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-26990918

RESUMO

Three boron diketonate chromophores with extended π-conjugated backbone were prepared and their spectroscopic features were investigated through a combined theoretical/experimental study. It was shown that these complexes, which undergo very large electronic reorganization upon photoexcitation, combine large two-photon absorption cross section with an emission energy and quantum efficiency in solution that is strongly dependent on solvent polarity. The strong positive influence of boron complexation on the magnitude of the two-photon absorption was clearly established, and it was shown that the two-photon absorption properties were dominated by the quadrupolar term. For one of the synthesized compounds, intense one- and two-photon-induced solid-state emission (fluorescence quantum yield of 0.65 with maximum wavelength of 610 nm) was obtained as a result of antiparallel J-aggregate crystal packing.

17.
Phys Chem Chem Phys ; 17(45): 30318-27, 2015 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-26506886

RESUMO

We have studied the interaction of a polymeric water soluble anthracenyl derivative () with salmon testes DNA. The results from UV-Vis, fluorescence, Fourier transform infrared (FT-IR) and circular dichroism spectroscopies indicate that the groove binding process regulates the interaction between and DNA. The binding constants, calculated by absorption spectroscopy at 298, 304 and 310 K, were equal to 3.2 × 10(5) M(-1), 4.7 × 10(5) M(-1), and 6.6 × 10(5) M(-1) respectively, proving a relatively high affinity of for salmon testes DNA. Results of Hoechst 33258 displacement assays strongly support the groove binding mode of to DNA. The association stoichiometry of the :DNA adduct was found to be 1 for every 5 base pairs. FT-IR spectra, recorded at different /DNA molar ratios, indicate the involvement of the phosphate groups and adenine and thymine DNA bases in the association process. Thermodynamic results suggest that hydrophobic forces regulate the binding of with DNA without excluding some extent of involvement of van der Waals forces and hydrogen bonding arising due to surface binding between the hydrophilic polymeric arms of the ligand and the functional groups positioned on the edge of the groove. The resulting composite biomaterial could constitute a valuable candidate for future biological and/or photonic applications.


Assuntos
Antracenos/química , Materiais Biocompatíveis/química , DNA/química , Polímeros/química , Testículo/química , Animais , Dicroísmo Circular , Masculino , Salmão , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Água/química
18.
Macromol Rapid Commun ; 36(1): 55-9, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25353390

RESUMO

Tuning the chain-end functionality of a short-chain cationic homopolymer, owing to the nature of the initiator used in the atom transfer radical polymerization (ATRP) polymerization step, can be used to mediate the formation of a gel of this poly(electrolyte) in water. While a neutral end group gives a solution of low viscosity, a highly homogeneous gel is obtained with a phosphonate anionic moiety, as characterized by rheometry and diffusion nuclear magnetic resonance (NMR). This novel type of supramolecular control over poly(electrolytic) gel formation could find potential use in a variety of applications in the field of electro-active materials.


Assuntos
Ácidos Fosforosos/síntese química , Polímeros/síntese química , Técnicas Eletroquímicas , Géis , Polimerização , Viscosidade
19.
J Phys Chem A ; 118(23): 4038-47, 2014 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-24835334

RESUMO

Although it has been reported in a few instances that the spectroscopic properties of cyanine dyes were strongly dependent on the nature of the chemical substitution of their central carbon atom, there has not been to date any systematic study specifically aimed at rationalizing this behavior. In this article, such a systematic study is carried out on an extended family of 17 polymethine dyes carrying different substituents on their central carbon, some of those being specifically synthesized for this study, some of those similar to previously reported compounds, for the sake of comparison. Their absorption properties, which spread over the whole visible to near-infrared spectral range, are seen to be dramatically dependent on the electron-donating character of this central substituent. By correlating this behavior to NMR spectroscopy and (vibronic) TD-DFT calculations, we show that it results from a profound modification of the ground state electronic configuration, namely, a progressive localization of the cationic charge on the central carbon as the electron-donating nature of the central substituent is increased.

20.
Inorg Chem ; 52(19): 10705-7, 2013 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-24020389

RESUMO

A new type of dinuclear iridium complex, based on a quadrupolar Schiff base ligand, is synthesized and its structure fully characterized. Its linear and nonlinear spectroscopic properties are investigated, evidencing a strong contribution of the metal-to-ligand transitions not only to the linear absorption but also to the two- and three-photon absorption properties.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA