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1.
Spectrochim Acta A Mol Biomol Spectrosc ; 215: 327-333, 2019 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-30852279

RESUMEN

The changing of the electronic and vibronic states due to the insertion of Zn(II), Cu(II), Ni(II) or Co(II) ions in the meso-tetrakis(4-pyridyl)porphyrin ring center is investigated. The combination of absorption, photoluminescence, Raman and infrared spectroscopies with second-derivative-based spectral deconvolution analysis reveals that the structuration of both B- and Q-bands is very sensitive to the decorating ion. Similar to free base porphyrins, metal(II) meso-tetra(4-pyridyl)porphyrins also present their Q-band constituted of multiple electronic transitions, where the central ion plays an important role in the selection of vibration modes that mediate the vibronic transitions. Our novel results will expand and reinterpret current assignments for metal(II) meso-tetra(4-pyridyl)porphyrins vibrational modes available in the literature.

2.
Photochem Photobiol Sci ; 13(8): 1213-24, 2014 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-24967638

RESUMEN

The influence of the polypyridyl ligand on the photophysics of fac-[Re(CO)3(NN)(bpa)](+), bpa = 1,2-bis-(4-pyridyl)ethane and NN = 1,10-phenanthroline (phen), pyrazino[2,3-f][1,10]-phenanthroline (dpq), and dipyrido[3,2-a:2'3'-c]phenazine (dppz) has been investigated by steady state and time-resolved emission spectroscopy combined with theoretical calculations using time-dependent density functional theory (TD-DFT). The fac-[Re(CO)3(phen)(bpa)](+) is a typical MLCT emitter in acetonitrile with ϕ = 0.11 and τ = 970 ns. The emission lifetime and quantum yield decrease significantly in fac-[Re(CO)3(dpq)(bpa)](+) (ϕ = 0.05; τ = 375 ns) due to the presence of a close lying dark charge transfer state located at the pyrazine ring of dpq, as indicated by TD-DFT data. The luminescence of these complexes is quenched by hydroquinone with kq = (2.9 ± 0.1) × 10(9) and (2.6 ± 0.1) × 10(9) L mol(-1) s(-1), respectively, for NN = phen or dpq. These values are increased respectively to (4.6 ± 0.1) × 10(9) and (4.2 ± 0.1) × 10(9) L mol(-1) s(-1) in the 1 : 1 H2O-CH3CN mixture. In this medium Stern-Volmer constants determined by steady-state and time-resolved measurements differ from each other, which is indicative of static quenching, i.e. the pre-association of hydroquinone and the complexes through hydrogen bonding between the remote N-atom in the bpa ligand (KA ≅ 1-2 × 10(1) L mol(-1)), followed by a concerted proton-electron transfer. In contrast to other investigated complexes, fac-[Re(CO)3(dppz)(bpa)](+) is weakly emissive in acetonitrile at room temperature (ϕ ≅ 10(-4)) and does not exhibit a rigidochromic effect. This photophysical behaviour as well as TD-DFT data indicate that the lowest lying triplet excited state can be described as (3)ILdppz. The results provide additional insight into the influence of the polypyridyl ligand on the photophysical properties of Re(I) complexes.


Asunto(s)
Compuestos Organometálicos/química , Renio/química , Ligandos , Luminiscencia , Modelos Moleculares , Estructura Molecular , Fenantrolinas/química , Procesos Fotoquímicos , Pirazinas/química , Piridinas/química , Teoría Cuántica , Espectrofotometría
3.
J Phys Chem A ; 116(1): 18-26, 2012 Jan 12.
Artículo en Inglés | MEDLINE | ID: mdl-22168904

RESUMEN

The present work employs a set of complementary techniques to investigate the influence of outlying Ru(II) groups on the ground- and excited-state photophysical properties of free-base tetrapyridyl porphyrin (H(2)TPyP). Single pulse and pulse train Z-scan techniques used in association with laser flash photolysis, absorbance and fluorescence spectroscopy, and fluorescence decay measurements, allowed us to conclude that the presence of outlying Ru(II) groups causes significant changes on both electronic structure and vibrational properties of porphyrin. Such modifications take place mainly due to the activation of nonradiative decay channels responsible for the emission quenching, as well as by favoring some vibrational modes in the light absorption process. It is also observed that, differently from what happens when the Ru(II) is placed at the center of the macrocycle, the peripheral groups cause an increase of the intersystem crossing processes, probably due to the structural distortion of the ring that implies a worse spin-orbit coupling, responsible for the intersystem crossing mechanism.

4.
Int J Pharm ; 332(1-2): 153-60, 2007 Mar 06.
Artículo en Inglés | MEDLINE | ID: mdl-17056212

RESUMEN

Psoralens are widely used for the treatment of hyperproliferative skin disease. In this work, we prepared nanoparticles (NP) containing a benzopsoralen (3-ethoxy carbonyl-2H-benzofuro[3,2-f]-1-benzopiran-2-one) by the solvent evaporation technique. We evaluated important NP parameters such as particle size, drug encapsulation efficiency, effect of the encapsulation process over the drug's photochemistry, zeta potential, external morphology, and in vitro release behavior. We also investigated the nanoparticle as a drug delivery system (DDS), as well as its target delivery to the action site, which is a very important parameter to increase the therapeutic use of psoralens and to reduce their side effects. The uptake of benzopsoralen-loaded PLGA nanoparticles by different kinds of cells found in rat peritoneal exudates was also studied. The photodamage promoted by irradiation with UV light revealed morphological characteristics of cell damage such as cytoplasmic vesiculation, mitochondrial damage, and swelling of both the granular endoplasmatic reticulum and nuclear membrane. This encapsulation method maintained the drug's properties and improved drug delivery to the target cell.


Asunto(s)
Líquido Ascítico/metabolismo , Fármacos Dermatológicos/metabolismo , Portadores de Fármacos , Furocumarinas/metabolismo , Ácido Láctico/química , Nanopartículas , Terapia PUVA , Fármacos Fotosensibilizantes/metabolismo , Ácido Poliglicólico/química , Polímeros/química , Animales , Líquido Ascítico/citología , Líquido Ascítico/efectos de los fármacos , Química Farmacéutica , Fármacos Dermatológicos/química , Fármacos Dermatológicos/farmacología , Fármacos Dermatológicos/efectos de la radiación , Composición de Medicamentos , Endocitosis , Furocumarinas/química , Furocumarinas/farmacología , Furocumarinas/efectos de la radiación , Técnicas In Vitro , Cinética , Masculino , Tamaño de la Partícula , Fármacos Fotosensibilizantes/química , Fármacos Fotosensibilizantes/farmacología , Fármacos Fotosensibilizantes/efectos de la radiación , Copolímero de Ácido Poliláctico-Ácido Poliglicólico , Ratas , Ratas Wistar , Solubilidad , Propiedades de Superficie , Tecnología Farmacéutica/métodos , Rayos Ultravioleta
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