Efeito de variações estruturais sobre as propriedades magnéticas e a luminescência de complexos de lantanídeos com ligantes polidentados derivados de diaminas

Orientadora: Profa. Dra. Jaísa Fernandes SoaresCoorientadoras: Profa. Dra. Giovana Gioppo Nunes, Profa. Dra. Andreia Gerniski MacedoTese (doutorado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Programa de Pós-Graduação em Química. Defesa : Curitiba, 12/05/2023Inclui referênciasResumo: Complexos de íons Ln3+ têm ganhado destaque devido às suas propriedades magnéticas e de fotoluminescência, sendo candidatos promissores a aplicações tecnológicas como o armazenamento de informação de densidade muito alta e a fabricação de dispositivos óticos. No âmbito do magnetismo molecular, compostos de coordenação e organometálicos contendo os íons Tb3+, Dy3+ e Er3+ podem exibir anisotropia magnética alta, característica de suma importância para promover a relaxação lenta da magnetização nos denominados Single-Molecule Magnets (SMM). Por outro lado, complexos de Tb3+ e Eu3+ contendo ligantes que promovam o efeito antena e que desfavoreçam os caminhos de decaimento não radiativo podem operar como excelentes fotoemissores. Com base na distribuição de densidade dos elétrons 4f, a qual possui forte dependência angular, é possível explorar estratégias sintéticas que partem da escolha adequada dos ligantes a fim de modular tanto as propriedades magnéticas quanto óticas dos produtos. Neste sentido, num primeiro momento neste trabalho, foi realizada a síntese de quelantes polidentados N,O-doadores (ou exclusivamente N-doadores) derivados de diaminas e com estruturas análogas à do pré-ligante N,N’-bis(2-hidroxibenzil)-N,N’-bis(2-metilpiridil)-1,2-etilenodiamina (H2bbpen) já reportado na literatura. Dentre os produtos de síntese, o N,N’-bis(2- hidroxibenzil)-N,N’-bis(2-metilquinolil)-1,2-etilenodiamina (H2bbqen) e o N,N’-bis(2- hidroxibenzil)-N,N’-bis(2-metilquinolil)-1,2-propanodiamina (H2bbqpn) são inéditos. Num segundo momento, foram realizadas reações entre os pré-ligantes sintetizados e os íons de terras raras de interesse (Y3+, Eu3+, Gd3+, Tb3+, Dy3+). Todos os produtos de síntese foram caracterizados por técnicas espectroscópicas e de análise estrutural e elementar, além das análises concernentes às propriedades de interesse, como medidas de susceptometria DC e AC (na presença de campo magnético estático e oscilante, respectivamente) e de fotoemissão. Assim, dois novos SMM de desempenho magnético excelente foram sintetizados, o [Dy(bbppn)X] (X = Cl??, 1, ou Br??, 3; bbppn2- = N,N’-bis(2-oxidobenzil)-N,N’-bis(2-metilpiridil)-1,2- propanodiamina). Graças à anisotropia magnética alta e à estabilidade de 1 em solução, sua atividade potencial como agente de deslocamento químico por pseudocontato (PCS) na Ressonância Magnética Nuclear foi investigada. Nos estudos de variações estruturais nos ligantes, realizados com o objetivo de promover uma mudança do perfil de solubilidade de 1, os complexos inéditos [Dy(bbppn)(dmso)2]Cl (1-dmso, dmso = dimetilsulfóxido) e [Dy(bbppn-NO2)Cl] (1-NO2; H2bbppn- NO2 = N,N’-bis(2-hidroxi-5-nitro-benzil)-N,N’-bis(2-metilquinolil)-1,2-propano-diamina) foram sintetizados; o comportamento de SMM de 1-dmso foi confirmado. Cálculos computacionais em nível ab initio foram determinantes na racionalização dos resultados distintos de desempenho magnético dos produtos 1, 3 e 1-dmso. Nos estudos de propriedades óticas, os complexos 1, [Tb(bbppn)Cl] (4) e [Eu(bbppn)Cl] (5) foram avaliados. O complexo 4 mostrou rendimento quântico intrínseco de emissão excelente, acima de 90%. Tal resultado deve-se provavelmente à desativação de caminhos específicos para o quenching da emissão em resposta à substituição na região alifática da diamina. Em resumo, este trabalho contribui para o entendimento da correlação entre as propriedades estruturais, óticas e magnéticas de complexos de Ln3+ com ligantes polidentados derivados de diaminas.Abstract: Ln3+ complexes have gained prominence due to their magnetic and photoluminescent properties, being promising candidates for technological applications such as very high-density information storage and the manufacture of optical devices. In molecular magnetism, coordination and organometallic compounds containing Dy3+, Er3+ and Tb3+ can exhibit high magnetic anisotropy, a characteristic of paramount importance to promote the slow relaxation of magnetization in the so-called Single-Molecule Magnets (SMM). On the other hand, Tb3+ and Eu3+ complexes containing ligands that promote the antenna effect and disfavor non-radiative decay pathways can operate as excellent photoemitters. Based on the electron density distribution of the 4f orbitals, which has a strong angular dependence, it is possible to explore synthetic strategies starting from the adequate choice of ligands to modulate the products' magnetic and optical properties. In this sense, in the first step of this work, we synthesized N,O-donor polydentate ligands (or exclusively N-donors) derived from diamines whose structures are similar to that of the proligand N,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-methylpyridyl)- 1,2-ethylenediamine (H2bbpen) already reported in the literature. Among the synthesis products, N,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-methylquinolyl)-1,2-ethylenediamine (H2bbqen) and N,N'-bis(2- hydroxybenzyl)-N,N'-bis(2-methylquinolyl)-1,2- propanediamine (H2bbqpn) are unprecedented. In a second step, reactions were carried out between the proligands and the rare-earth ions of interest (Y3+, Eu3+, Gd3+, Tb3+, Dy3+). All synthesis products were characterized by spectroscopic techniques, structural and elemental analysis, and analyses concerning the properties of interest, such as DC and AC susceptometry measurements (in the presence of static and oscillating magnetic fields, respectively) and photoemission. Thus, two new SMM with excellent magnetic performance were synthesized, the [Dy(bbppn)X] (X = Cl??, 1, or Br??, 3; H2bbppn = N,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-methylpyridyl)-1,2- propanediamine). Thanks to the high magnetic anisotropy and the stability of 1 in solution, its potential activity as a pseudocontact chemical shift agent (PCS) in Nuclear Magnetic Resonance was investigated. In studies of structural variations in ligands, which were carried out to promote a change in the solubility profile of 1, the unpublished complexes [Dy(bbppn)(dmso)2]Cl (1-dmso, dmso = dimethylsulfoxide) and [Dy(bbppn-NO2)Cl] (1-NO2; H2bbppn-NO2 = N,N'-bis(2-hydroxy-5-nitro-benzyl)- N,N'-bis(2-methylquinolyl)-1,2-propanediamine) were synthesized; for 1-dmso, SMM behavior has been confirmed. Computational calculations at the ab initio level were instrumental in rationalizing the magnetic performance results of 1, 3 and 1-dmso. Additionally, the optical properties of complexes 1, 4, [Tb(bbppn)Cl], and 5, [Eu(bbppn)Cl], were evaluated. Complex 4 showed excellent photoemission, with an intrinsic emission quantum yield above 90%. This result is probably due to the deactivation of specific pathways for emission quenching in response to substitution in the diamine aliphatic region. In summary, this work contributes to understanding the correlation between the structural, optical and magnetic properties of Ln3+ complexes with polydentate ligands derived from diamines

Crystal Structures of 3-halo-2-organochalcogenylbenzo[b]chalcogenophenes

The structure of the title compounds 3-bromo-2-(phenyl­sulfan­yl)benzo[b]thiophene (C(14)H(9)BrS(2); 1), 3-iodo-2-(phenyl­sulfan­yl)benzo[b]thio­phene (C(14)H(9)IS(2); 2), 3-bromo-2-(phenyl­selan­yl)benzo[b]seleno­phene (C(14)H(9)BrSe(2); 3), and 3-iodo-2-(phenyl­selan­yl)benzo[b]seleno­phene (C(14)H(9)ISe(2); 4) were determined by single-crystal X-ray diffraction; all structures presented monoclinic (P2(1)/c) symmetry. The phenyl group is distant from the halogen atom to minimize the steric hindrance repulsion for all structures. Moreover, the structures of 3 and 4 show an almost linear alignment of halogen–selenium–carbon atoms arising from the intra­molecular orbital inter­action between a lone pair of electrons on the halogen atom and the anti­bonding σ*(Se–C) orbital (n (halogen)→σ*(Se–C)). This inter­action leads to significant differences in the three-dimensional packing of the mol­ecules, which are assembled through π–π and C—H⋯π inter­actions. These data provide a better comprehension of the inter­molecular packing in benzo[b]chalcogenophenes, which is relevant for optoelectronic applications

Accessing decavanadate chemistry with tris(hydroxymethyl)aminomethane, and evaluation of methylene blue bleaching

Two decavanadates (trisH)4[H2V10O28]·10H2O ( 1 ) and (trisH)6[V10O28] ( 2 ) have been synthesised from NaVO3 or V2O5 in an aqueous solution of tris(hydroxymethyl)aminomethane (tris). Bimetallic derivatives [Cu(OH2)5(trisH)]2[V10O28]·6H2O ( 3 ) and [Cu(OH2)3(2–amp)]2(trisH)2 [V10O28]·2H2O ( 4 ) were obtained by the addition of CuCl2 or CuCl2 / 2–amp (2–(aminomethyl)pyridine) to the route that gave 2 . The products were characterised by single-crystal X-ray diffractometry, thermogravimetric analysis, FTIR, Raman and EPR spectroscopies. Moreover, 4 was effective in bleaching a methylene blue (MB) solution under natural light in acidic media by either degradation of the dye or precipitation of a MB-decavanadate salt depending on the experimental conditions

An oxalate-bridged oxidovanadium(iv) binuclear complex that improves the in vitro cell uptake of a fluorescent glucose analog

The centrosymmetric oxidovanadium(IV) complex (Et 3NH) 2[{VO(OH 2)(ox)} 2(μ–ox)] (I), where ox 2− = oxalate, was synthesized and characterized by X-ray diffraction (single-crystal and powder, PXRD), thermogravimetric (TGA), magnetic susceptibility (at room temperature) and spectroscopic analyses (infrared, Raman and electron paramagnetic resonance, EPR, spectroscopies). In the solid state, each vanadium center is coordinated by the oxygen atoms of a bis-bidentate oxalate bridging ligand, a terminal oxalate, an oxo group and one water molecule. The electronic structure of the binuclear complex was investigated by density functional theory (DFT) calculations, both in vacuum and in a simulated aqueous environment, employing the ωB97XD functional and the def2TZVP basis set. The cytotoxicity of I was evaluated in vitro in the human hepatocellular carcinoma cell line HepG2, giving an IC 50 value of 15.67 µmol L −1 after incubation for 24 h. The EPR analysis of I in aqueous solution suggested the maintenance of the binuclear structure, while in the hyperglycemic medium DMEM the complex suffers dissociation to give a mononuclear oxidovanadium(IV) species. HepG2 cell treatment with 0.10 and 0.50 µmol L −1 of I in DMEM increased 2-NBDG (2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-D-glucose) uptake significantly (up to 91% as compared to HepG2 in hyperglycemic condition, 59%). These results indicate a promising activity of I to be investigated further in additional antidiabetic studies

Seven-coordinate Tb3+ complexes with 90% quantum yields: High-performance examples of combined singlet- and triplet-to-Tb3+ energy-transfer pathways

Seven-coordinate, pentagonal-bipyramidal (PBP) complexes [Ln(bbpen)Cl] and [Ln(bbppn)Cl], in which Ln = Tb3+ (products I and II), Eu3+ (III and IV), and Gd3+ (V and VI), with bbpen2- = N,N′-bis(2-oxidobenzyl)-N,N′-bis(pyridin-2-ylmethyl)ethylenediamine and bbppn2- = N,N′-bis(2-oxidobenzyl)-N,N′-bis(pyridin-2-ylmethyl)-1,2-propanediamine, were synthesized and characterized by single-crystal X-ray diffraction analysis, alternating-current magnetic susceptibility measurements, and photoluminescence (steady-state and time-resolved) spectroscopy. Under a static magnetic field of 0.1 T, the Tb3+ complexes I and II revealed single-ion-magnet behavior. Also, upon excitation at 320 nm at 300 K, I and II presented very high absolute emission quantum yields (0.90 ± 0.09 and 0.92 ± 0.09, respectively), while the corresponding Eu3+ complexes III and IV showed no photoluminescence. Detailed theoretical calculations on the intramolecular energy-transfer rates for the Tb3+ products indicated that both singlet and triplet ligand excited states contribute efficiently to the overall emission performance. The expressive quantum yields, QLnL, measured for I and II in the solid state and a dichloromethane solution depend on the excitation wavelength, being higher at 320 nm. Such a dependence was rationalized by computing the intersystem crossing rates (WISC) and singlet fluorescence lifetimes (τS) related to the population dynamics of the S1 and T1 levels. Thin films of product II showed high air stability and photostability upon continuous UV illumination, which allowed their use as downshifting layers in a green light-emitting device (LED). The prototypes presented a luminous efficacy comparable with those found in commercial LED coatings, without requiring encapsulation or dispersion of II in host matrixes. The results indicate that the PBP environment determined by the ethylenediamine (en)-based ligands investigated in this work favors the outstanding optical properties in Tb3+ complexes. This work presents a comprehensive structural, chemical, and spectroscopic characterization of two Tb3+ complexes of mixed-donor, en-based ligands, focusing on their outstanding optical properties. They constitute good molecular examples in which both triplet and singlet excited states provide energy to the Tb3+ ion and lead to high values of QLnL

Rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART): Study protocol for a randomized controlled trial

Background: Acute respiratory distress syndrome (ARDS) is associated with high in-hospital mortality. Alveolar recruitment followed by ventilation at optimal titrated PEEP may reduce ventilator-induced lung injury and improve oxygenation in patients with ARDS, but the effects on mortality and other clinical outcomes remain unknown. This article reports the rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART). Methods/Design: ART is a pragmatic, multicenter, randomized (concealed), controlled trial, which aims to determine if maximum stepwise alveolar recruitment associated with PEEP titration is able to increase 28-day survival in patients with ARDS compared to conventional treatment (ARDSNet strategy). We will enroll adult patients with ARDS of less than 72 h duration. The intervention group will receive an alveolar recruitment maneuver, with stepwise increases of PEEP achieving 45 cmH(2)O and peak pressure of 60 cmH2O, followed by ventilation with optimal PEEP titrated according to the static compliance of the respiratory system. In the control group, mechanical ventilation will follow a conventional protocol (ARDSNet). In both groups, we will use controlled volume mode with low tidal volumes (4 to 6 mL/kg of predicted body weight) and targeting plateau pressure <= 30 cmH2O. The primary outcome is 28-day survival, and the secondary outcomes are: length of ICU stay; length of hospital stay; pneumothorax requiring chest tube during first 7 days; barotrauma during first 7 days; mechanical ventilation-free days from days 1 to 28; ICU, in-hospital, and 6-month survival. ART is an event-guided trial planned to last until 520 events (deaths within 28 days) are observed. These events allow detection of a hazard ratio of 0.75, with 90% power and two-tailed type I error of 5%. All analysis will follow the intention-to-treat principle. Discussion: If the ART strategy with maximum recruitment and PEEP titration improves 28-day survival, this will represent a notable advance to the care of ARDS patients. Conversely, if the ART strategy is similar or inferior to the current evidence-based strategy (ARDSNet), this should also change current practice as many institutions routinely employ recruitment maneuvers and set PEEP levels according to some titration method.Hospital do Coracao (HCor) as part of the Program 'Hospitais de Excelencia a Servico do SUS (PROADI-SUS)'Brazilian Ministry of Healt

Stability in solution and chemoprotection by octadecavanadates(IV/V) in E. coli cultures

Two mixed-valence octadecavanadates, (NH 4) 2(Me 4N) 5[V IV 12V V 6O 42I]·Me 4NI·5H 2O (V 18I) and [{K 6(OH 2) 12V IV 11V V 7O 41(PO 4)·4H 2O} n] (V 18P), were synthesized and characterized by single-crystal X-ray diffraction analysis and FTIR, Raman, 51V NMR, EPR and UV/Vis/NIR spectroscopies. The chemoprotective activity of V 18I and V 18P towards the alkylating agent diethyl sulfate was assessed in E. coli cultures. The complex V 18I was nontoxic in concentrations up to 5.0 mmol L −1, while V 18P presented moderate toxicity in the concentration range 0.10 - 10 mmol L −1. Conversely, a ca. 35% enhancement in culture growth as compared to cells treated only with diethyl sulfate was observed upon addition of V 18I (0.10 to 2.5 mmol L −1), while the combination of diethyl sulfate with V 18P increased the cytotoxicity presented by diethyl sulfate alone. 51V NMR and EPR speciation studies showed that V 18I is stable in solution, while V 18P suffers partial breakage to give low nuclearity oxidometalates of vanadium(V) and (IV). According to the results, the chemoprotective effect depends strongly on the direct reactivity of the polyoxidovanadates (POV) towards the alkylating agent. The reaction of diethyl sulfate with V 18I apparently produces a new, rearranged POV instead of poorly-reactive breakage products, while V 18P shows the formation and subsequent consumption of low-nuclearity species. The correlation of this chemistry with that of other mixed-valence polyoxidovanadates, [H 6V IV 2V V 12O 38PO 4] 5- (V 14) and [V IV 8V V 7O 36Cl] 6- (V 15), suggests a relationship between stability in solution and chemoprotective performance

Effects of Decavanadate Salts with Organic and Inorganic Cations on Escherichia coli, Giardia intestinalis, and Vero Cells

Decavanadate salts with nicotinamide (3-pyridinecarboxamide, 3-pca) and isonicotinamide (4-pyridinecarboxamide, 4-pca) in both neutral and protonated forms, (3-Hpca) 4 [H 2 V 10 O 28 ]·2H 2 O·2(3-pca) (complex I) and (4-Hpca) 4 [H 2 V 10 O 28 ]·2(4-pca) (complex II), have been synthesized and characterized by vibrational spectroscopy (infrared and Raman), thermogravimetric analysis (TGA), 51 V NMR, and single-crystal X-ray diffraction analysis. The effects of sodium decavanadate (henceforth called NaV 10 ) and compounds I and II on Escherichia coli, Giardia intestinalis, and Vero (African green monkey epithelial kidney) cells were evaluated. Enhanced growth inhibitory activity against E. coli cultures was observed upon treatment with products I and II when compared to that with NaV 10 (GI 50 values of 2.8, 4.0, and 11 mmol L -1 , respectively), as well as lower cell viability as measured by the intake of propidium iodide (PI). Exposure of Giardia trophozoites to NaV 10 and II revealed reduction in trophozoite viability (GI 50 values of ca. 10 μmol L -1 ) and affected the parasite adherence to both polystyrene culture tubes and a monolayer of Vero cells, even at low concentrations. A lesser effect on Giardia was shown for I. Furthermore, all three compounds were significantly less toxic to Vero cells than the reference drug, albendazole, employed in the treatment of giardiasis. Toxicity reports of oxidovanadium compounds toward Giardia are unprecedented and open a path to the development of new therapeutic agents