New phenoxyl radical complexes of manganese, gallium, indium and iron based on an H2bbpen ligand derivative

Anjos, Ademir dos; Bortoluzzi, Adaílton J.; Miguel, Sara; Peralta, Rosely A.; Friedermann, Geraldo R.; Mangrich, Antônio S.; Neves, Ademir

doi:10.1590/s0103-50532006000800009

Cited by 19 publications

(7 citation statements)

References 25 publications

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“…In this context, considerable effort has been made in the development of heterofunctional ligands containing (soft and hard) N, O, and S binding sites, suitable for the coordination of a range of p-, d-, and f-block metal ions. For example, the well-known proligand H 2 bbpen ( N,N’ -bis(2-hydroxybenzyl)- N,N’ -bis(pyridin-2-ylmethyl)ethylenediamine) and its derivatives have been used to prepare complexes with first-row transition-metal ions as models for metalloenzymes, − and with Ln 3+ ions for nuclear medicine and magnetic studies . This potentially hexadentate proligand presents two relatively soft nitrogen atoms on the pyridine rings and four harder donor atoms, two amine nitrogens and two oxygen atoms on the phenol groups. , A variation of H 2 bbpen, the molecule N,N′- bis(2-hydroxylbenzyl) -N,N′ -bis(pyridin-2-ylmethyl)-1,2-propanediamine), H 2 bbppn , , presents one additional methyl group attached to the ethylenediamine backbone and produces complexes with a similar coordination environment about the metal ion, but with lower symmetry in comparison to those obtained with H 2 bbpen .…”

Section: Introductionmentioning

confidence: 99%

Promoting a Significant Increase in the Photoluminescence Quantum Yield of Terbium(III) Complexes by Ligand Modification

et al. 2019

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Two discrete mononuclear complexes, [Tb(bbpen)(NO 3 )] (I) and [Tb(bbppn)(NO 3 )] (II), for which H 2 bbpen = N,N′-bis(2-hydroxybenzyl)-N,N′-bis(pyridin-2-ylmethyl)ethylenediamine and H 2 bbppn = N,N′-bis(2-hydroxylbenzyl)-N,N'-bis(pyridin-2-ylmethyl)-1,2-propanediamine, were synthesized and characterized by FTIR, Raman, and photoluminescence (PL, steady-state and time-resolved modes) spectroscopy. The attachment of a methyl group to the ethylenediamine portion of the ligand backbone differentiates II from I and acts as a determining feature to both the structural and optical properties of the former. The single-crystal X-ray structure of H 2 bbppn is described here for the first time, while that of complex II has been redetermined in the monoclinic C2 space group in light of new diffraction data. In II, selective crystallization leads to spontaneous resolution of enantiomeric molecules in different crystals. Absolute emission quantum yields (ϕ) and luminescence excited-state lifetimes (at room temperature and 11 K) were measured for both complexes. Despite their similar molecular structures, I and II exhibit remarkably different ϕ values of 21 ± 2% and 67 ± 7%, respectively, under UV excitation at room temperature. Results of quantum-mechanical (DFT and TD-DFT) calculations and experimental PL measurements also performed for H 2 bbpen and H 2 bbppn confirmed that both ligands are suitable to work as "antennas" for Tb III . Considering the 5 D 4 lifetime profiles and the significantly higher absolute quantum yield of II, it appears that thermally active nonradiative pathways present in I are minimized in II due to differences in the conformation of the ethylenediamine bridge.

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Section: Introductionmentioning

confidence: 99%

Promoting a Significant Increase in the Photoluminescence Quantum Yield of Terbium(III) Complexes by Ligand Modification

et al. 2019

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“…At t = 0 (red line), a peak at 580 nm is associated with the dark yellow solution of 2 . This peak has been found in other Mn(III) complexes 54 and has been shown to be attributed to the ligand-to-metal charge transfer that occurs between the amide nitrogen p-orbital and the d-orbital of the Mn(III) metal center 55 . When t = 0 and t = 5 scans were compared, no significant changes in this peak were observed.…”

Section: Resultsmentioning

confidence: 59%

Polydopamine-Coated Manganese Complex/Graphene Nanocomposite for Enhanced Electrocatalytic Activity Towards Oxygen Reduction

Parnell

Chhetri

Brandt

et al. 2016

Sci Rep

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Platinum electrodes are commonly used electrocatalysts for oxygen reduction reactions (ORR) in fuel cells. However, this material is not economical due to its high cost and scarcity. We prepared an Mn(III) catalyst supported on graphene and further coated with polydopamine, resulting in superior ORR activity compared to the uncoated PDA structures. During ORR, a peak potential at 0.433 V was recorded, which is a significant shift compared to the uncoated material’s −0.303 V (both versus SHE). All the materials reduced oxygen in a wide pH range via a four-electron pathway. Rotating disk electrode and rotating ring disk electrode studies of the polydopamine-coated material revealed ORR occurring via 4.14 and 4.00 electrons, respectively. A rate constant of 6.33 × 106 mol−1s−1 was observed for the polydopamine-coated material–over 4.5 times greater than the uncoated nanocomposite and superior to those reported for similar carbon-supported metal catalysts. Simply integrating an inexpensive bioinspired polymer coating onto the Mn-graphene nanocomposite increased ORR performance significantly, with a peak potential shift of over +730 mV. This indicates that the material can reduce oxygen at a higher rate but with lower energy usage, revealing its excellent potential as an ORR electrocatalyst in fuel cells.

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“…2 Não há nenhum processo relacionado diretamente ao íon metálico Ga(III), uma vez que o mesmo é inerte eletroquimicamente. 51 Através de técnicas eletroanalíticas, como a voltametria cíclica, é possível determinar a atividade antioxidante de substâncias. Essas técnicas podem correlacionar potenciais de oxidação, intensidade de corrente e/ou outros parâmetros eletroquímicos com a capacidade antioxidante, sendo mais seletivas e sensíveis que os métodos espectrofotométricos.…”

Section: Avaliação Da Atividade Antioxidanteunclassified

Síntese, caracterização e estudo das propriedades de um novo complexo mononuclear contendo quercetina e íon Ga(III)

et al. 2013

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Recebido em 27/2/12; aceito em 23/10/12; publicado na web em 20/2/13 SYNTHESIS, CHARACTERIZATION AND STUDY OF THE PROPERTIES OF A NEW MONONUCLEAR QUERCETIN COMPLEX CONTAINING Ga(III) IONS. Flavonoids are one of the most important compound groups applied as medicine given their antioxidant properties, but several intrinsic properties can be improved through structural modifications to their molecules. Here, the synthesis and characterization of a new gallium (III) complex with quercetin is described. Electrochemical properties, as well as antioxidant and cytotoxic activities, were investigated and compared to the free flavonoid molecule. The mononuclear complex obtained, [Ga(C 15 INTRODUÇÃOOs flavonoides são compostos de baixa massa molar com uma estrutura base constituída por dois anéis aromáticos (A e B) ligados através de um anel pirano (C), como pode ser visualizado na Figura 1. Eles representam um dos grupos fenólicos mais importantes e diversificados entre os produtos de origem natural, sendo amplamente distribuídos no reino vegetal.1 Nos últimos anos essas moléculas têm atraído a atenção de muitos pesquisadores, pois exibem notável variedade de atividades biológicas, físicas e farmacológicas.2,3 Elas podem atuar como sequestradores de radicais livres, neutralizando espécies reativas de oxigênio, e como ligantes quelatos para íons metálicos, sendo que se atribui a essas características a responsabilidade por suas propriedades benéficas. 4,5 A quercetina (Figura 1) é um dos flavonoides mais presentes na dieta humana, pois é encontrada em grande quantidade nas frutas, verduras e chás. Possui propriedades de grande interesse, entre elas estão seus efeitos anticarcinogênicos, protetores do sistema renal, cardiovascular e hepático.6 A interação dos flavonoides com íons metálicos pode mudar as propriedades antioxidantes e alguns outros efeitos biológicos, sendo a maioria de suas propriedades muitas vezes superiores às dos compostos originais.3 Pesquisas têm mostrado que alguns complexos metálicos com a quercetina possuem resistência à atividade neoplasmática e apresentam atividades antisséptica, anti--inflamatória e/ou antioxidante. 7O gálio atua em nosso organismo em focos de inflamação e infecção particularmente nos neutrófilos granulosos e leucócitos polimorfonucleares.8 O principal interesse clínico do gálio deriva da observação de que suas propriedades metabólicas são similares às do ferro.9-11 Desde os anos 70, o gálio mostrou-se eficaz na diminuição da reabsorção óssea acelerada, redução associada aos níveis plasmáticos elevados de cálcio ou inibidores da proliferação neoplásica, tornando-se o segundo íon metálico depois da platina, a ser utilizado no tratamento de câncer.10 Entretanto, seus sais trivalentes (Ga 3+ ) são fracamente absorvidos pelo intestino e alguns derivados são susceptíveis à hidrólise, diminuindo, assim, sua eficiência biológica.11 Por isso o grande interesse na síntese de compostos de coordenação com o íon metálico, visando uma possível correção dessas deficiências. Estudos demonstr...

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New phenoxyl radical complexes of manganese, gallium, indium and iron based on an H2bbpen ligand derivative

Cited by 19 publications

References 25 publications

Promoting a Significant Increase in the Photoluminescence Quantum Yield of Terbium(III) Complexes by Ligand Modification

Promoting a Significant Increase in the Photoluminescence Quantum Yield of Terbium(III) Complexes by Ligand Modification

Polydopamine-Coated Manganese Complex/Graphene Nanocomposite for Enhanced Electrocatalytic Activity Towards Oxygen Reduction

Síntese, caracterização e estudo das propriedades de um novo complexo mononuclear contendo quercetina e íon Ga(III)

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