Examinando por Autor "Pizarro, Nancy"
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Ítem Comparitive study on structural, magnetic and spectroscopic properties of four new copper(II) coordination polymers with 4′-substituted terpyridine ligands(Academic Press Inc., 2017-09) Toledo, Dominique; Vega, Andrés; Pizarro, Nancy; Baggio, Ricardo; Peña, Octavio; Roisnel, Thierry; Pivan, Jean-Yves; Moreno, YankoThe synthesis and characterization of four copper(II) complexes with different terpyridyl ligands have been carried out, their crystal and molecular structures determined and their magnetic and luminescent properties analyzed. The ligands used in the coordination reactions were 4′-(3-methyl-2-thienyl)-4,2′:6′,4''-terpyridine (4-stpy), -4′-(4-quinolinyl)-4,2′:6′,4''-terpyridine (4-qtpy), 4′-(4-quinolinyl)-3,2′:6′,3''-terpyridine (3-qtpy, unreported so far) and 4′-(4-cyanophenyl)-4,2′:6′,4''-terpyridine (4-cntpy); the reaction of these ligands with Cu(II)-hexafluoroacetylacetone (Cu(hfacac)2) gives rise to coordination polymers Cu(4-stpy)(hfacac)2 (I), Cu(4-qtpy)(hfacac)2 (II), Cu(3-qtpy)(hfacac)2 (III) and Cu(4-cntpy)(hfacac)2 (IV). The different location of the nitrogen atom of the outer ring is responsible for the different coordination modes. The emission spectra of dichloromethane solutions are consistent with dissociation of the complexes; the emission maxima simulate those of the free ligands. The emission of I, III and IV in the solid state is essentially quenched upon complexation with Cu(II), whereas for compound II an emission at 420 nm is observed. The interaction between copper centers has been related with the coplanarity of terpyridine rings. Complexes I–III exhibit a paramagnetic behavior, while compound IV, with the smallest torsion angle between pyridine moieties, shows an antiferromagnetic behavior described by a dimeric model, with J=−4.38 cm−1, g =2.06 and ρ=0.07. © 2017 Elsevier Inc.Ítem Electronic and Photophysical Properties of Re I (CO) 3 Br Complexes Modulated by Pyrazolyl-Pyridazine Ligands(ACS Omega, 2019-03-04) Saldías, Marianela; Guzmán, Nicolas; Palominos, Franco; Sandoval-Altamirano, Catalina; Gunther, German; Pizarro, Nancy; Vega, AndresThe direct reaction of a series of substituted (1H-pyrazol-1-yl)pyridazine (L I : 6-(1H-pyrazolyl)pyridazine; L II : 3-chloro-6-(1H-pyrazole-1-yl)-pyridazine; L III : 6-(1H-3,5-dimethylpyrazolyl)pyridazine-3-carboxylic acid; L IV : 3,6-bis-N-pyrazolyl-pyridazine; and L V : 3,6-bis-N-3-methylpyrazolyl-pyridazine) with the bromotricarbonyl(tetrahydrofuran)-rhenium(I) dimer leads to the monometallic complexes [(L X )Re(CO) 3 Br] (I-V), which displays a nonregular octahedral geometry around the Re I center and a fac-isomerism for the carbonyl groups, whereas pyridazine and pyrazolyl rings remain highly coplanar after coordination to rhenium. Cyclic voltammetry shows one irreversible oxidation and one irreversible reduction for each compound as measured in N,N-dimethylformamide. Oxidation ranges from 0.94 V for III to 1.04 V for I and have been attributed to the Re I /Re II couple. In contrast, the reductions are ligand centered, ranging from -1.64 V for II to -1.90 V for III and V. Density functional theory calculations on the vertical one electron oxidized and one electron reduced species, using the gas-phase optimized geometry for the neutral complex confirm this assignment. Compounds I-V show two absorption bands, one around 410 nm (metal-to-ligand charge transfer (MLCT), Re dπ → π∗) and the other at ∼300 nm (intraligand, π → π∗). Excitation at 400 nm at 77 K leads to unstructured and monoexponential emission with large Stokes shift, whose maxima vary between 570 (III) and 636 (II) nm. The quantum yields for these emissions in solution are intensified strongly going from air to argon equilibrated solution. Singlet oxygen quantum yields change from 0.03 (III) to 0.21 (IV). These data are consistent with emission from 3 MLCT. The emission undergoes a bathochromic shift when R 1 is a π-donating group (Cl or N-pyrazolyl) and a hypsochromic shift for a π-acceptor (COOH). The bimolecular emission quenching rate constant by triethylamine (TEA) for II, IV, and V is 1.09, 0.745, and 0.583 × 10 8 M -1 s -1 , respectively. Photolysis in dichloromethane-CO 2 saturated solution with TEA as a sacrificial electron donor leads in all cases to formic acid generation.Ítem Fatty Acid Conjugates of Toluidine Blue O as Amphiphilic Photosensitizers: Synthesis, Solubility, Photophysics and Photochemical Properties(Blackwell Publishing Inc., 2021-01) Robinson-Duggon, José; Pizarro, Nancy; Gunther, Germán; Zúñiga-Núñez, Daniel; Edwards, Ana María; Greer, Alexander; Fuentealba, DenisToluidine blue O (TBO) is a water-soluble photosensitizer that has been used in photodynamic antimicrobial and anticancer treatments, but suffers from limited solubility in hydrophobic media. In an effort to incrementally increase TBO’s hydrophobicity, we describe the synthesis of hexanoic (TBOC6) and myristic (TBOC14) fatty acid derivatives of TBO formed in low to moderate percent yields by condensation with the free amine site. Covalently linking 6 and 14 carbon chains led to modifications of not only TBO’s solubility, but also its photophysical and photochemical properties. TBOC6 and TBOC14 derivatives were more soluble in organic solvents and showed hypsochromic shifts in their absorption and emission bands. The solubility in phosphate buffer solution was low for both TBOC6 and TBOC14, but unexpectedly slightly greater in the latter. Both TBOC6 and TBOC14 showed decreased triplet excited-state lifetimes and singlet oxygen quantum yields in acetonitrile, which was attributed to heightened aggregation of these conjugates particularly at high concentrations due to the hydrophobic “tails.” While in diluted aqueous buffer solution, indirect measurements showed similar efficiency in singlet oxygen generation for TBOC14 compared to TBO. This work demonstrates a facile synthesis of fatty acid TBO derivatives leading to amphiphilic compounds with a delocalized cationic “head” group and hydrophobic “tails” for potential to accumulate into biological membranes or membrane/aqueous interfaces in PDT applications.Ítem Flavonoids in microheterogeneous media, relationship between their relative location and their reactivity towards singlet oxygen(Public Library of Science, 2015-06) Günther, Germán; Berrîos, Eduardo; Pizarro, Nancy; Valdés, Karina; Montero, Guillermo; Arriagada, Francisco; Morales, JavierIn this work, the relationship between the molecular structure of three flavonoids (kaempferol, quercetin and morin), their relative location in microheterogeneous media (liposomes and erythrocyte membranes) and their reactivity against singlet oxygen was studied. The changes observed in membrane fluidity induced by the presence of these flavonoids and the influence of their lipophilicity/hydrophilicity on the antioxidant activity in lipid membranes were evaluated by means of fluorescent probes such as Laurdan and diphenylhexatriene (DPH). The small differences observed for the value of generalized polarization of Laurdan (GP) curves in function of the concentration of flavonoids, indicate that these three compounds promote similar alterations in liposomes and erythrocyte membranes. In addition, these compounds do not produce changes in fluorescence anisotropy of DPH, discarding their location in deeper regions of the lipid bilayer. The determined chemical reactivity sequence is similar in all the studied media (kaempferol < quercetin < morin). Morin is approximately 10 times more reactive than quercetin and 20 to 30 times greater than kaempferol, depending on the medium. Copyright: © 2015 Günther et al.Ítem New Light-Green Thermally Activated Delayed Fluorescence Polymer Based on Dimethylacridine-Triphenyltriazine Light-Emitting Unit and Tetraphenylsilane Moiety as Non-Conjugated Backbone(MDPI, 2023-01) Hauyon, René A.; Fuentealba, Denis; Pizarro, Nancy; Ortega-Alfaro, María C.; Ugalde-Saldívar, Víctor M.; Sobarzo, Patricio A.; Medina, Jean; García, Luis; Jessop, Ignacio A.; González-Henríquez, Carmen M.; Tundidor-Camba, Alain; Terraza, Claudio A.In the search for solution-processable TADF materials as a light emitting layer for OLED devices, polymers have attracted considerable attention due to their better thermal and morphological properties in the film state with respect to small molecules. In this work, a new polymer (p-TPS-DMAC-TRZ) with thermally activated delayed fluorescence (TADF) light-emitting characteristics was prepared from a conjugation-break unit (TPS) and a well-known TADF core (DAMC-TRZ). This material was designed to preserve the photophysical properties of DAMC-TRZ, while improving other properties, such as thermal stability, promoted by its polymerization with a TPS core. Along with excellent solubility in common organic solvents such as toluene, chloroform and THF, the polymer (Mn = 9500; Mw = 15200) showed high thermal stability (TDT5% = 481 °C), and a Tg value of 265 °C, parameters higher than the reference small molecule DMAC-TRZ (TDT5% = 305 °C; Tg = 91 °C). The photoluminescence maximum of the polymer was centered at 508 nm in the solid state, showing a low redshift compared to DMAC-TRZ (500 nm), while also showing a redshift in solution with solvents of increasing polarity. Time-resolved photoluminescence of p-TPS-DMAC-TRZ at 298 K, showed considerable delayed emission in solid state, with two relatively long lifetimes, 0.290 s (0.14) and 2.06 s (0.50), and a short lifetime of 23.6 ns, while at 77 K, the delayed emission was considerably quenched, and two lifetimes in total were observed, 24.6 ns (0.80) and 180 ns (0.20), which was expected from the slower RISC process at lower temperatures, decreasing the efficiency of the delayed emission and demonstrating that p-TPS-DMAC-TRZ has a TADF emission. This is in agreement with room temperature TRPL measurements in solution, where a decrease in both lifetime and delayed contribution to total photoluminescence was observed when oxygen was present. The PLQY of the mCP blend films with 1% p-TPS-DMAC-DMAC-TRZ as a dopant was determined to be equal to 0.62, while in the pure film, it was equal to 0.29, which is lower than that observed for DMAC-TRZ (0.81). Cyclic voltammetry experiments showed similarities between p-TPS-DMAC-TRZ and DAMC-TRZ with HOMO and LUMO energies of −5.14 eV and −2.76 eV, respectively, establishing an electrochemical bandgap value of 2.38 eV. The thin film morphology of p-TPS-DMAC-TRZ and DMAC-TRZ was compared by AFM and FE-SEM, and the results showed that p-TPS-DMAC-TRZ has a smoother surface with fewer defects, such as aggregations. These results show that the design strategy succeeded in improving the thermal and morphological properties in the polymeric material compared to the reference small molecule, while the photophysical properties were mostly maintained, except for the PLQY determined in the pure films. Still, these results show that p-TPS-DMAC-TRZ is a good candidate for use as a light-emitting layer in OLED devices, especially when used as a host-guest mixture in suitable materials such as mCP. © 2022 by the authors.Ítem Photochemistry of P,N-bidentate rhenium(i) tricarbonyl complexes: Reactive species generation and potential application for antibacterial photodynamic therapy(Royal Society of Chemistry, 2021-09) Acosta, Alison; Antipán, Javier; Fernández, Mariano; Prado, Gaspar; Sandoval-Altamirano, Catalina; Günther, Germán; Gutiérrez-Urrutia, Izabook; Poblete-Castro, Ignacio; Vega, Andrés; Pizarro, NancyIn this work, we describe the photoisomerization of facial rhenium(i) tricarbonyl complexes bearing P,N-bidentate pyridyl/phosphine ligands with different chelating rings and anions: RePNBr, RePNTfO, and RePNNBr, which are triggered under irradiation at 365 nm in solutions. The apparent photodegradation rate constants (kapp) depend on the coordinating ability of the solvent, being lowest in acetonitrile. The kapp value increases as the temperature rises, suggesting a reactive IL excited state thermally populated from the MLCT excited state involved. Using the Eyring equation, positive activation enthalpies (ΔH≠) accompanied by high negative values for the activation entropy (ΔS≠) were obtained. These results suggest whatever the P,N-ligand or anion, the reaction proceeds through a strongly solvated or a compact transition state, which is compatible with an associative mechanism for the photoisomerization. A 100-fold decrease in the log10 CFU value is observed for E. coli and S. aureus in irradiated solutions of the compounds, which follows the same tendency as their singlet oxygen generation quantum yield: RePNBr > RePNTfO > RePNNBr, while no antibacterial activity is observed in the darkness. This result indicates that the generation of singlet oxygen plays a key role in the antibacterial capacity of these complexes. © The Royal Society of Chemistry.Ítem Photodegradation of nimodipine and felodipine in microheterogeneous systems(Sociedad Chilena de Química, 2012) Brito, Julio; Pozo, Andrés; García, Cristóbal; Núñez-Vergara, Luis J.; Morales, Javier; Günther, Germán; Pizarro, NancyThe photochemical behavior of nimodipine (NIMO) and felodipine (FELO), photolabile drugs widely used as antihypertensive calcium channel blockers, is studied in constrained media. Specifically, we are interested in the kinetic analysis of 4-aryl-1,4-dihydropyridine photodegradation processes when they are incorporated in biological-mimicking systems like micelles or liposomes. In order to establish if the nature of the head of surfactant (ionic or nonionic) could be important modulating the photo-reactivity of these drugs, we studied the photodegradation of NIMO and FELO incorporated in micelles formed with sodium dodecyl sulfate (SDS, anionic), dodecyl-pyridinium chloride (DPC, cationic) and mono lauryl sucrose ester (MLS, nonionic) as surfactants. Additionally, the results of the photodegradation of these compounds in liposomes were also included. The results clearly indicate that both dihydropyridines studied, NIMO and FELO, are located near to the interface, but the surface charge of micelles does not affect neither, the photodegradation rate constant nor the photodegradation products profile. The absence of singlet oxygen generation in micellar media is consistent with the proposition of these 4-aryl-1,4-dihidropyridines located near to the interface of the micelle, where a polar environment is sensed. In addition, the ethanol preferential location on membranes and dihydropyridine enhanced photodegradation by alcohol presence are interesting results to consider in future research.Ítem Rhenium(I) bromo tricarbonyl complexes from anthracenyl derivatized ligands(2023-07) Muñoz, José; Rojas, Xavier; Palominos, Franco; Arce, Roxana; Cañas, Francisco; Pizarro, Nancy; Vega, AndrésThe ligand 2-(1H-pyrazol-1-yl)pyrazine (pypyr) was prepared by reaction of 2-bromopyrazine with N-lithium pyrazolate with 92.5% yield, while the anthracenyl derivatives 2-(anthracen-9-yl)-5-(1H-pyrazol-1-yl)pyrazine (pypyr-anthra) and 9,10-bis(5-(1H-pyrazol-1-yl)pyrazin-2-yl)anthracene (pypyr-anthra-pypyr) were prepared by reaction of the 9-anthraceneboronic or bis-boronic acid pinacol ester with 2-bromo-5-(1H-pyrazol-1-yl)pyrazine with medium yields (49.6 and 31.5 % respectively). The respective ReI(CO)3Br complexes: [(pypyr)Re(CO)3Br], [(pypyr-anthra)Re(CO)3Br] and [Br(CO)3Re(pypyr-anthra-pypyr)Re(CO)3Br] were prepared in high yields (94, 84 and 78 % respectively) by reaction with bromotricarbonyl(tetrahydrofuran)rhenium(I) dimer. DFT modelling suggests the anthracenyl moiety is not coplanar with the pyrazolyl-pyrazine fragment, defining a dihedral angle of 65° and 67° for [(pypyr-anthra)Re(CO)3Br] and [Br(CO)3Re(pypyr-anthra-pypyr)Re(CO)3Br] respectively. Each one of the three rhenium(I) molecules shows a quasi-reversible reduction wave around − 1.10 V, assigned by comparison with the uncoordinated ligand, the pypyr fragment, while additional reductions waves related to this core or the anthryl arms are present. UV–Vis spectra show absorption bands and/or shoulders around 400–450 nm for the series of compounds in solution. The respective extinction coefficients (∼4 × 103 M−1cm−1), the sensitivity to solvent polarity and DFT modelling suggest they corresponds to MLCT Redπ → π(pyr)* transitions. Despite their high emissivity, the uncoordinated ligands completely lose their emission upon coordinated to ReI(CO)3Br. The rhenium(I) complexes emit around 650 nm upon excitation, although [(pypyr)Re(CO)3Br] is a moderate emissive molecule, while [(pypyr-anthra)Re(CO)3Br] and [Br(CO)3Re(pypyr-anthra-pypyr)Re(CO)3Br] are very weak ones. In contrast these two last molecules showed a remarkably high yield as singlet oxygen sensitizers. © 2023 Elsevier LtdÍtem Synthesis and Optical Properties of a Novel Hybrid Nanosystem Based on Covalently Modified nSiO2 Nanoparticles with a Curcuminoid Molecule(Multidisciplinary Digital Publishing Institute (MDPI), 2024-06) Parra-Muñoz, Nicole; López-Monsalves, Valentina; Espinoza-González, Rodrigo; Aravena, Daniel; Pizarro, Nancy; Soler, MonicaA new curcuminoid molecule (3) has been designed and synthesized, containing a central -(CH2)2-COOH chain at the α carbon of the keto-enol moiety in the structure. The carboxylic acid group is added to react with exposed amino groups on silica oxide nanoparticles (nSiO2), forming an amide bond to attach the curcuminoid moiety to the nSiO2 covalently. The Kaiser test quantifies the functionalization degree, yielding 222 μmol of curcuminoid per gram of nanoparticles. The synthesized hybrid nanosystem, nSiO2-NHCO-CCM, displays significant emission properties, with a maximum emission at 538 nm in dichloromethane, similar to curcuminoid 1 (without the central chain), which emits at 565 nm in the same solvent. Solvent-induced spectral effects on the absorption and emission bands of the new hybrid nanosystem are confirmed, similar to those observed for the free curcuminoid (1). The new nanosystem is evaluated in the presence of kerosene in water, showing an emission band at 525 nm as a detection response. The ability of nSiO2-NHCO-CCM to change its fluorescence when interacting with kerosene in water is notable, as it overcomes the limitation caused by the insolubility of free curcuminoid 1 in water, allowing for the exploitation of its properties when connected to the water-stable nanosystem for future detection studies.Ítem Synthesis, Physicochemical and Photophysical Characterization of 4-(1-Pyrenyl)-butyl-α-D-mannopyranoside(Sociedade Brasileira de Química, 2016) Sandoval, Catalina; Arriagada, Franco S.; De la Fuente, Julio R.; Sanchez, Susana A.; Morales, Javier; Pizarro, Nancy; Nonelle, Santi; Gunther, GermanGlycolipids are biomolecules composed of a lipid chain (lipophilic) and a monosaccharide or oligosaccharide as hydrophilic group. Their chemical structure and biological role make them undoubtedly good candidates for a large and continuously growing number of biotechnological applications. Mannose is a carbohydrate present on membrane glycolipids of a wide number of pathogenic microorganisms (bacteria, fungi, protozoa, and viruses) and specifically recognized by several lectins. We synthesized a mannose derivative linked through a short methylene chain to a pyrene moiety which behaves as a surfactant, able to aggregate, and retains the photophysical properties of pyrene: showing comparable absorption and emission spectra, having lower fluorescence quantum yield and the ability to form excimer, and finally the ability to produce O2(1Δg) with high quantum yields. Thus, this novel molecule would open future applications for detection (fluorescence) or inactivation (singlet oxygen) of bacterial pathogens, viruses, tumor cells, or particular cells.Ítem The binuclear dual emitter [Br(CO)3Re(P⋯N)(N⋯P)Re(CO)3Br] (P⋯N): 3-chloro-6-(4-diphenylphosphinyl)butoxypyridazine, a new bridging: P, N -bidentate ligand resulting from the ring opening of tetrahydrofuran(Royal Society of Chemistry, 2017) Saldías, Marianela; Manzur, Jorge; Palacios, Rodrigo E.; Gómez, María L.; Fuente, Julio De La; Günther, Germán; Pizarro, Nancy; Vega, AndrésLithium diphenylphosphide unexpectedly provokes the ring-opening of tetrahydrofuran (THF) and by reaction with 3,6-dichloropyridazine leads to the formation of the ligand 3-chloro-6-(4-diphenylphosphinyl)butoxypyridazine (P⋯N), which was isolated. The reaction of this ligand with the (Re(CO)3(THF)Br)2 dimer yields the novel complex [Br(CO)3Re(μ-3-chloro-6-(4-diphenylphosphinyl)butoxypyridazine)2Re(CO)3Br] (BrRe(P⋯N)(N⋯P)ReBr), which was crystallized in the form of a chloroform solvate, (C46H40Br2Cl2N4O8P2Re2)·(CHCl3). The monoclinic crystal (P21/n) displays a bimetallic cage structure with a symmetry inversion centre in the middle of the rhenium to rhenium line. The molecule shows two oxidation signals occurring at +1.50 V and +1.76 V which were assigned to the ReI/ReII and ReII/ReIII metal-centered couples, respectively, while signals observed at -1.38 V and -1.68 V were assigned to ligand centered reductions. Experimental and DFT/TDDFT results indicate that the UV-Vis absorption maximum of BrRe(P⋯N)(N⋯P)ReBr occurring near 380 nm displays a metal to ligand charge transfer (MLCT) character, which is consistent with CV results. Upon excitation at this wavelength, a weak emission (Φem < 1 × 10-3) is observed around 580 nm (in dichloromethane) which decays with two distinct lifetimes τ1 and τ2 of 24 and 4.7 ns, respectively. The prevalence of non-radiative deactivation pathways is consistent with efficient internal conversion induced by the high conformational flexibility of the P⋯N ligand's long carbon chain. Measurements in a frozen solvent at 77 K, where vibrational deactivation is hindered, show intense emission associated with the 3MLCT state. These results demonstrate that BrRe(P⋯N)(N⋯P)ReBr preserves the dual emitting nature previously reported for the mononuclear complex RePNBr, with emission associated with and states. © 2017 The Royal Society of Chemistry.