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2.
Clin Radiol ; 2024 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-38644074

RESUMO

AIM: To determine (a) the accuracy of ultrasound in detecting brachial plexus pathology and (b) outline the advantages and limitations of ultrasound compared to MRI for imaging the brachial plexus. MATERIAL AND METHODS: cases with clinically suspected brachial plexus pathology were evaluated first by ultrasound, followed by MRI. Patients with prior brachial plexus imaging were excluded. The final diagnosis was based on a combination of ultrasound, MRI, clinical follow-up, and surgical findings. The accuracy of the ultrasound was assessed by comparing the ultrasound and the final diagnoses. The mean clinical follow-up time following ultrasound was 1.8 ± 1.4 years. RESULTS: Ninety-two (64%) of the 143 cases had normal brachial plexus ultrasound and MRI examinations. Fifty-one (36%) of 143 cases had brachial plexus pathology on MRI, comprising post-radiation fibrosis (n=25, 49%), nerve sheath tumor (n=11, 21%), traumatic injury (n=7, 14%), inflammatory polyneuropathy (n=4, 8%), malignant infiltration (n=2, 4%), desmoid fibromatosis (n=1,2%), and neuralgic amyotrophy (n=1, 2%). Overall diagnostic accuracy of ultrasound for brachial plexus pathology was 98% (140/143), with three discordant cases (neuralgic amyotrophy n=1, inflammatory neuropathy n=1, postradiation fibrosis n=1) regarded as normal on ultrasound assessment. Sensitivity, specificity, and positive and negative predictive value of ultrasound for identifying brachial plexus pathology were 94%, 100%, 100%, and 97%, respectively. CONCLUSION: Ultrasound identifies brachial plexus pathology with high accuracy and specificity, showing comparable diagnostic efficacy to MRI. Ultrasound can serve as an effective first-line imaging investigation for suspected brachial plexus pathology.

3.
Public Health ; 218: 106-113, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-37011443

RESUMO

OBJECTIVES: The relationship between human mobility and nature of science (NOS) salience in the UK news media was examined. STUDY DESIGN: This is a mixed-method study. METHODS: A time series NOS salience data set was established from the content analysis of 1520 news articles related to non-pharmaceutical interventions of COVID-19. Data were taken from articles published between November 2021 and February 2022, which correlates with period of the change from pandemic to endemic status. Vector autoregressive model fitting with human mobility took place. RESULTS: The findings suggest that it was not the number of COVID-19 news articles nor the actual number of cases/deaths, but the specific NOS content that was associated with mobility change during the pandemic. Data indicate a Granger causal negative direction (P < 0.1) for the effect of the NOS salience represented in the news media on mobility in parks, as well as the effect of scientific practice, scientific knowledge and professional activities communicated in news media on recreational activities and grocery shopping. NOS salience was not associated with the mobility for transit, work or residential locations (P > 0.1). CONCLUSIONS: The findings of the study suggest that the ways in which the news media discuss epidemics can influence changes in human mobility. It is therefore essential that public health communicators emphasise the basis of scientific evidence to eliminate potential media bias in health and science communication for the promotion of public health policy. The present study approach, which combines time series and content analysis and uses an interdisciplinary lens from science communication, could also be adopted to other interdisciplinary health-related topics.


Assuntos
COVID-19 , Mídias Sociais , Humanos , COVID-19/epidemiologia , Pandemias , SARS-CoV-2 , Fatores de Tempo , Comunicação , Meios de Comunicação de Massa
4.
Osteoarthritis Cartilage ; 30(8): 1050-1061, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35460872

RESUMO

Joint-on-a-chip (JOC) models are powerful tools that aid in osteoarthritis (OA) research. These microfluidic devices apply emerging organ-on-a-chip technology to recapitulate a multifaceted joint tissue microenvironment. JOCs address the need for advanced, dynamic in vitro models that can mimic the in vivo tissue environment through joint-relevant biomechanical or fluidic integration, an aspect that existing in vitro OA models lack. There are existing review articles on OA models that focus on animal, tissue explant, and two-dimensional and three-dimensional (3D) culture systems, including microbioreactors and 3D printing technology, but there has been limited discussion of JOC models. The aim of this article is to review recent developments in human JOC technology and identify gaps for future advancements. Specifically, mechanical stimulation systems that mimic articular movement, multi-joint tissue cultures that enable crosstalk, and systems that aim to capture aspects of OA inflammation by incorporating immune cells are covered. The development of an advanced JOC model that captures the dynamic joint microenvironment will improve testing and translation of potential OA therapeutics.


Assuntos
Dispositivos Lab-On-A-Chip , Osteoartrite , Animais , Humanos , Engenharia Tecidual/métodos
7.
J Wound Care ; 24(11): 519, 522-4, 526-8, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26551644

RESUMO

OBJECTIVE: Material testing system is a conventional but destructive method for measuring the biomechanical properties of wound tissues in basic research. The recently developed optical coherence tomography-based air-jet indentation system is a non-destructive method for measuring these properties of soft tissues in a non-contact manner. The aim of the study was to examine the correlation between the biomechanical properties of wound tissues measured by the two systems. METHOD: Young male Sprague-Dawley rats with streptozotocin-induced diabetic were wounded by a 6 mm biopsy punch on their hind limbs. The biomechanical properties of wound tissues were assessed with the two systems on post-wounding days 3, 7, 10, 14, and 21. Wound sections were stained with picro-sirius red for analysis on the collagen fibres. Data obtained on the different days were charted to obtain the change in biomechanical properties across the time points, and then pooled to examine the correlation between measurements made by the two devices. Qualitative analysis to determine any correlation between indentation stiffness measured by the air-jet indentation system and the orientation of collagen fibres. RESULTS: The indentation stiffness is significantly negatively correlated to the maximum load, maximum tensile stress, and Young's modulus by the material testing system (all p<0.05). The orientation of collagen changes with the indentation stiffness over time. CONCLUSION: Our findings support the use of optical coherence tomography-based air-jet indentation system to evaluate the biomechanical properties of wounds in a non-contact manner. It is a potential clinical device to examine the biomechanical properties of chronic wounds in vivo in a repeatable manner.


Assuntos
Membro Posterior/lesões , Úlcera Cutânea/patologia , Ar , Animais , Fenômenos Biomecânicos , Diabetes Mellitus Experimental , Masculino , Teste de Materiais/métodos , Ratos , Ratos Sprague-Dawley , Úlcera Cutânea/enfermagem , Úlcera Cutânea/prevenção & controle , Tomografia de Coerência Óptica , Cicatrização
8.
Aliment Pharmacol Ther ; 37(5): 517-26, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23305043

RESUMO

BACKGROUND: A meta-analysis on the risk of hepatocellular carcinoma (HCC) among hepatitis B virus (HBV) genotypes is warranted as the current data are conflicting. AIM: To investigate the relative risk of HCC among the four major HBV genotypes (A-D). METHODS: A meta-analysis was performed based on literature search from electronic databases and bibliography between 1950 and 2012. All abstracts with keywords 'hepatitis B', 'hepatocellular carcinoma' and 'genotype' were screened. Studies were included if they reported HBV genotype as an exposure and HCC as an outcome. RESULTS: Nine hundred and eighty-eight abstracts were found through literature search, among them 43 studies were eligible for this meta-analysis. A total of 14,545 patients with an average age of 43 years were included; 71% were male patients and 17% had cirrhosis. In 33 studies, HCC was found in 1541/6060 (25%) genotype C vs. 550/4417 (12%) genotype B HBV-infected patients [odds ratio (OR) = 2.05, 95% confidence interval (CI) = 1.52-2.76, P < 0.001]. No difference in the risk of HCC was found among genotype A (71/517, 14%) vs. genotype D (170/1506, 11%) HBV-infected patients in 14 studies (OR = 0.94, 95% CI = 0.67-1.32). In 10 studies, the risk of HCC was also found higher among genotype C (498/1659, 30%) than genotype A&D (103/1403, 7%) HBV-infected patients (OR = 2.34, 95% CI = 1.63-3.34, P < 0.001). Subgenotype Ce and Cs HBV-infected patients had similar risk on HCC (OR = 1.13, 95% CI = 0.76-1.67, P = 0.54). On funnel plot analysis, there was no significant publication bias in all comparisons. CONCLUSION: Genotype C hepatitis B virus is associated with a higher risk of hepatocellular carcinoma than other major hepatitis B virus genotypes.


Assuntos
Carcinoma Hepatocelular/genética , Vírus da Hepatite B/genética , Neoplasias Hepáticas/genética , Adulto , DNA Viral/genética , Feminino , Genótipo , Humanos , Masculino , Fatores de Risco
9.
Opt Express ; 18(3): 1909-15, 2010 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-20174019

RESUMO

We report the first Fourier domain modelocked (FDML) laser constructed using optical parametric amplifier (OPA) in conjunction with an erbium-doped fiber amplifier (EDFA), centered at approximately 1555 nm, to the best of our knowledge. We utilize a one-pump OPA and a C-band EDFA in serial configuration with a tunable Fabry-Perot interferometer to generate a hybrid FDML spectrum. Results demonstrate a substantially better spectral shape, output power and stability than individual configurations, with decreased sensitivity to polarization changes. We believe this technique has the potential to enable several amplifiers to complement individual deficiencies resulting in improved spectral shapes and power generation for imaging applications such as optical coherence tomography (OCT).

10.
Neuroscience ; 133(4): 937-45, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-15964486

RESUMO

Extracellular ATP is well known as a neurotransmitter and neuromodulator in the CNS of adults. However, little is known about the involvement of ATP during the development of mammalian brain. In the present study, we have examined the expression pattern of P2X receptor subtype mRNA and protein during perinatal rat brain development (from embryonic day (E) 10 to postnatal day (P) 16 brain). While P2X3 receptors appeared early at E11, they declined in the stages that follow. P2X2 and P2X7 receptors were expressed from E14 onwards, while P2X4, P2X5 and P2X6 receptors were expressed from P1 onwards. P2X1 receptor expression was not observed in any of the developmental ages examined. We investigated the effect of 100 microM ATP and alpha,beta-methylene ATP (alpha,beta-meATP; selective agonist for P2X1, P2X2/3 and P2X3 receptors) on motor axon outgrowth in collagen-embedded neural tube explant cultures. Both ATP- and alpha,beta-meATP-treated neural tubes showed a significant reduction in neurite outgrowth compared with the control explants. This inhibitory effect could not be reproduced by uridine triphosphate. In conclusion, all P2X receptor subtypes, except for P2X1, were strongly represented in the developing rat brain. ATP was shown to inhibit motor axon outgrowth during early embryonic neurogenesis, most likely via the P2X3 receptor. It is speculated that P2X7 receptors may be involved in programmed cell death during embryogenesis and that P2X4, P2X(5) and P2X6 receptors might be involved in postnatal neurogenesis.


Assuntos
Axônios/fisiologia , Encéfalo/fisiologia , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Neurônios Motores/citologia , Receptores Purinérgicos P2/metabolismo , Trifosfato de Adenosina/análogos & derivados , Trifosfato de Adenosina/farmacologia , Análise de Variância , Animais , Animais Recém-Nascidos , Axônios/efeitos dos fármacos , Northern Blotting/métodos , Embrião de Mamíferos , Imuno-Histoquímica/métodos , Neurônios Motores/efeitos dos fármacos , Moléculas de Adesão de Célula Nervosa/metabolismo , Neuritos/efeitos dos fármacos , Neuritos/fisiologia , Técnicas de Cultura de Órgãos , RNA Mensageiro/biossíntese , Ratos , Receptores Purinérgicos P2/classificação , Receptores Purinérgicos P2/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodos
11.
Br J Radiol ; 75(891): 207-14, 2002 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-11932212

RESUMO

Diffusion weighted MRI was performed on patients with acute vertebral body compression. The usefulness of the apparent diffusion coefficient (ADC) in differentiating between benign and malignant fractures was evaluated. A total of 49 acute vertebral body compression fractures were found in 32 patients. 25 fractures in 18 patients were due to osteoporosis, 18 fractures in 12 patients were histologically proven to be due to malignancy, and 6 fractures in 2 patients were due to tuberculosis. Signal intensities on T(1) weighted, short tau inversion recovery (STIR) and diffusion weighted images were compared. ADC values of normal and abnormal vertebral bodies were calculated. Except for two patients with sclerotic metastases, benign acute vertebral fractures were hypointense and malignant acute vertebral fractures were hyperintense with respect to normal bone marrow on diffusion weighted images. Mean combined ADCs (ADC(cmb); average of the combined ADCs in the x, y and z diffusion directions) were 0.23 x 10(-3) mm(2) s(-1) in normal vertebrae, 0.82 x 10(-3) mm(2) s(-1) in malignant acute vertebral fractures and 1.94 x 10(-3) mm(2) s(-1) in benign acute vertebral fractures. The differences between ADC(cmb) values were statistically significant (p<0.001). The ADC is useful in differentiating benign from malignant acute vertebral body compression fractures, but there may be overlapping ADC values between malignant fractures and tuberculous spondylitis.


Assuntos
Fraturas Espontâneas/etiologia , Fraturas da Coluna Vertebral/etiologia , Neoplasias da Coluna Vertebral/diagnóstico , Neoplasias da Coluna Vertebral/secundário , Doença Aguda , Idoso , Diagnóstico Diferencial , Feminino , Fraturas Espontâneas/diagnóstico , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Osteoporose/complicações , Osteoporose/diagnóstico , Fraturas da Coluna Vertebral/diagnóstico , Tuberculose da Coluna Vertebral/complicações , Tuberculose da Coluna Vertebral/diagnóstico
12.
Inorg Chem ; 40(26): 6699-704, 2001 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-11735481

RESUMO

Reaction of [M(L-L)Cl(2)] [M = Pd, Pt; L-L = 4,4'-di-tert-butyl-2,2'-bipyridine ((t)Bu(2)bpy), 4,4'-dimethylcarboxylate-2,2'-bipyridine ((CO(2)Me)(2)bpy), bis(diphenylphosphino)methane (dppm)] with Na(2)S in refluxing methanol afforded [M(3)((t)Bu(2)bpy)(3)(mu(3)-S)(2)](2+) [M = Pd (1a), Pt (2a)], [M(3)((CO(2)Me)(2)bpy)(3)(mu(3)-S)(2)](2+) [M = Pd (1b), Pt (2b)], and [Pt(3)(dppm)(3)(mu(3)-S)(2)](2+) (3) as perchlorate salts. X-ray crystal analysis revealed that 1a, 1b, 2a, and 3 have triangular M(3)S(2) core structures. The three metal atoms in 1a, 2a, and 3 form virtual equilateral triangles with intramolecular Pd-Pd and Pt-Pt separations of 3.027(1)-3.065(1) and 3.104(1)-3.154(1) A, respectively. An isosceles triangle of Pd(3) atoms is observed in the molecular structure of 1b. The (1)MLCT absorption of 2a and 2b appears at 415 and 448 nm, respectively, in dichloromethane and is significantly red-shifted from the lowest energy absorption band of the Pd(3) analogues. Complex 1a exhibits weak photoluminescence in the solid state at 77 and 298 K (uncorrected lambda(max) 760 and 730 nm, respectively) while the 77 K solid-state emission of 1b (uncorrected lambda(max) 760 nm) is also weak. At 77 K, complexes 2a, 2b, and 3 display broad unstructured emissions at lambda(max) 616-630 nm in the solid state. Ligand-field excited states are tentatively assigned for these emissions.

13.
Phytochemistry ; 58(8): 1277-80, 2001 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-11738422

RESUMO

The 18-(13-->12 beta)-abeo-lanostene triterpenoid acid, ananosic acid A (1), and the dibenzocyclooctadiene lignan, ananosin A (2), were isolated from the stem bark of Kadsura ananosma. Their structures were elucidated by extensive spectral studies and the structure of 1 was confirmed by single crystal X-ray diffraction analysis.


Assuntos
Lignanas/química , Schisandraceae/química , Triterpenos/química , Cristalografia por Raios X , Lignanas/isolamento & purificação , Conformação Molecular , Triterpenos/isolamento & purificação
14.
Chemistry ; 7(19): 4180-90, 2001 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-11686597

RESUMO

We present the synthesis and photophysical and electroluminescent properties for a series of platinum(II) alpha-diimine bis(arylacetylide) complexes. The molecular structures of five derivatives have been elucidated by X-ray crystallography. Intermolecular pi-pi interactions (between aromatic diimine and phenylacetylide moieties) are apparent in the crystal lattices of two of these. All bis(phenylacetylide) derivatives exhibit intense triplet metal-to-ligand charge transfer (MLCT) photoluminescence in the solid state and in fluid solutions at room temperature. The impact of different solvents, substituents on the diimine ligands, and complex concentrations upon their emissive behavior have been examined and demonstrates that their emission energies can be systematically modified. Application of the 3MLCT excited state of the [Pt(alpha-diimine) (C(triple bond)CPh)2] materials in single- and double-layer organic light-emitting devices are described. The bis(butadiynyl) complex [Pt(4,4'-dtbpy)(C(triple bond)C-C(triple bond)CPh)2] (dtbpy = 4,4'-di-tert-butyl-2,2'-bipyridine) displays strong solid-state and solution phosphorescence at 77 and 298 K; the associated excited state is proposed to arise from both acetylenic 3pi pi*(C(triple bond)C-C(triple bond)CPh) and 3MLCT [Pt --> pi*(diimine)] transitions.

15.
Chemistry ; 7(18): 3998-4006, 2001 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-11596942

RESUMO

Reactions of MS4(2-) (M = Mo, W) with M'(PCy3)X (M'=Ag/Au, X= ClO4/Cl) and [Cu2(dcpm)2(MeCN)2](ClO4)2 (dcpm = bis(dicyclohexylphosphino)methane) afforded heterometallic sulfido clusters [M'2(PCy3)2(MS4)] (M=Mo, M'=Au: 2; M=W, M'=Ag: 3, Au: 4) and [Cu4(dcpm)4(MS4)](ClO4)2 (M=Mo: 5 x (ClO4)2, W: 6 x (ClO4)2), all of which, except 4, have been characterized by X-ray structure determination. Clusters 5 x(ClO4)2 and 6 x (ClO4)2 feature unusual 16-membered [Cu4P5C4] metallamacrocycles formed on the respective tetrathiometalate anion templates and have unusually long Cu-S bonds and Cu...M distances for metal sulfur clusters that contain a saddle-shaped [Cu4MS4] core. Low-energy absorption bands are observed in their electronic spectra at approximately 562 and 467 nm, respectively, assignable to MMCT transitions; quasireversible reduction waves are observed with E(1/2) = -1.43 (52+) and -1.78 V (62+) versus FeCp2(0/+); and they are emissive either in the solid state or in solution. The emission of 6(2+) can be quenched by both electron acceptors, such as methylviologen, or electron donors, such as aromatic amines, with the excited state reduction potential E(62+*/6+) estimated to be approximately 1.13V versus a normal hydrogen electrode.

16.
J Cell Biochem ; 83(3): 463-72, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11596114

RESUMO

Elfin (previously named CLIM1) is a protein that possesses an N-terminal PDZ domain and a C-terminal LIM domain. It belongs to the family of Enigma proteins. Enigma proteins are a family of cytoplasmic proteins that contain an N-terminal PDZ domain and a series of C-terminal LIM domains. By virtue of these two protein interacting domains, Enigma proteins are capable of protein-protein interactions. It has been proposed that Enigma proteins may act as adapters between kinases and the cytoskeleton. We have previously shown that Elfin is most abundantly expressed in the heart and it colocalizes with alpha-actinin 2 at the Z-disks of the myocardium. In this report, Elfin was shown to localize at the actin stress fibers of myoblasts, as revealed by green fluorescent protein (GFP) tagging. In situ hybridization and immunostaining showed that Elfin expression begins at an early stage in mouse development and is present throughout the developing heart. Taken together, our experimental results suggest that Elfin may play an important role in myofibrillogenesis and heart development.


Assuntos
Regulação da Expressão Gênica no Desenvolvimento , Coração/embriologia , Miocárdio/metabolismo , Fatores de Transcrição/biossíntese , Fatores de Transcrição/química , Actinina/metabolismo , Sequência de Aminoácidos , Animais , Linhagem Celular , Citoplasma/metabolismo , Citoesqueleto/metabolismo , DNA Complementar/metabolismo , Proteínas de Fluorescência Verde , Hibridização In Situ , Proteínas com Domínio LIM , Proteínas Luminescentes/metabolismo , Camundongos , Dados de Sequência Molecular , Ligação Proteica , Estrutura Terciária de Proteína , RNA Mensageiro/metabolismo , Homologia de Sequência de Aminoácidos , Fibras de Estresse/metabolismo , Fatores de Tempo , Distribuição Tecidual
17.
Am J Pathol ; 159(2): 609-22, 2001 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-11485919

RESUMO

Secreted protein acidic and rich in cysteine (SPARC) is an extracellular Ca(2+)-binding matricellular glycoprotein that associates with cell populations undergoing migration, morphogenesis, and differentiation. Studies on endothelial cells have established that its principal functions in vitro are counteradhesion and antiproliferation. The mechanism(s) underlying these antitumor effects is unknown. In this study, we showed that SPARC expression in ovarian cancer cells is inversely correlated with the degree of malignancy. The immunohistochemical data presented here confirmed the importance of diminished SPARC expression in ovarian cancer development. Treating human ovarian surface epithelial cells and ovarian cancer cells with SPARC revealed that as SPARC inhibits the proliferation of both normal and cancer cells, it induces apoptosis only in cancer cells. This observation indicates that down-regulation of SPARC is essential for ovarian carcinogenesis as cancer cells become sensitized to the apoptotic activity of SPARC during malignant transformation. We also showed here the first direct evidence that putative SPARC receptors are present on ovarian epithelial cells. Their levels are higher in human ovarian surface epithelial cells than cancer cells. Binding of SPARC to its receptor is likely to trigger tissue-specific signaling pathways that mediate its tumor suppressing functions. Decrease in ligand-receptor interaction by the down-regulation of SPARC and/or its receptor is essential for ovarian carcinogenesis.


Assuntos
Apoptose/fisiologia , Osteonectina/farmacologia , Osteonectina/fisiologia , Neoplasias Ovarianas/patologia , Ovário/citologia , Apoptose/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Células Cultivadas , Células Epiteliais/citologia , Células Epiteliais/efeitos dos fármacos , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Imuno-Histoquímica , Marcação In Situ das Extremidades Cortadas , Cinética , Osteonectina/genética , Ovário/efeitos dos fármacos , Células Tumorais Cultivadas
19.
Chemistry ; 7(11): 2306-17, 2001 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-11446633

RESUMO

The interactions between dioxoruthenium(VI) porphyrins 1 with N-phenylhydroxylamine or unsubstituted hydroxylamine are described. Reaction of complexes 1 with excess PhNHOH leads to isolation of bis(nitrosobenzene)ruthenium(II) porphyrins 3 and mono(nitrosobenzene)ruthenium(II) porphyrins 4. Both the types of ruthenium complexes are characterized by 1H NMR, IR, and UV/Vis spectroscopy, and mass spectrometry. The X-ray structure determinations on [Ru(II)(TPP)(PhNO)2] (3a), [Ru(II)(2,6-Cl-TPP)(PhNO)2] (3e), and [Ru(II)(4-MeO-TPP)(PhNO)(PhNH2)] (4d) (TPP tetraarylporphyrin) disclose a unidentate nitrosoarene coordination in all these complexes, with Ru-N(PhNO) bond lengths of 2.003(3) (3a, average), 1.991(3) (3e, average), and 2.042(2) A (4d). In the case of 4d, the Ru-N(PhNH2) bond length is found to be 2.075(3) A. Mechanistic investigations reveal the formation of intermediates [Ru(II)(Por)(PhNO)(PhNHOH)] (5; Por=porphyrin), a ruthenium complex with N-substituted hydroxylamine ligand, in the "1 + PhNHOH" system. The Ru-NH(OH)Ph moiety in 5 undergoes no rapid exchange with free PhNHOH in solution at room temperature, as revealed by 1H NMR spectroscopy. Unlike the interaction between complexes 1 and PhNHOH, reaction of such complexes with NH2OH affords nitrosylruthenium(II) porphyrins [Ru(II)(Por)(NO)(OH)] (6).


Assuntos
Hidroxilaminas/química , Metaloporfirinas/química , Compostos Nitrosos/química , Rutênio/química , Catálise , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Estrutura Molecular , Espectrofotometria Ultravioleta , Relação Estrutura-Atividade , Difração de Raios X
20.
J Am Chem Soc ; 123(21): 4985-91, 2001 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-11457326

RESUMO

The synthesis and X-ray structural and spectroscopic characterization for LAuC triple bond CAuL x 4CHCl(3) and LAuC triple bond C--C triple bond CAuL x 2CH(2)Cl(2) (1 x 4CHCl(3) and 2 x 2CH(2)Cl(2), respectively; L = PCy(3), tricyclohexylphosphine) are reported. The bridging C(n)(2-) units are structurally characterized as acetylene or diacetylene units, with C triple bond C distances of 1.19(1) and 1.199(8) A for 1 x 4CHCl(3) and 2 x 2CH(2)Cl(2), respectively. An important consequence of bonding to Au(I) for the C(n)(2-) moieties is that the lowest-energy electronic excited states, which are essentially acetylenic (3)(pi pi*) in nature, acquire sufficient allowedness via Au spin-orbit coupling to appear prominently in both electronic absorption and emission spectra. The origin lines for both complexes are well-defined and are observed at 331 and 413 nm for 1 and 2, respectively. Sharp vibronic progressions corresponding to v(C triple bond C) are observed in both emission and absorption spectra. The acetylenic (3)(pi pi) excited state of 2 has a long lifetime (tau(0) = 10.8 mus) in dichloromethane at room temperature and is a powerful reductant (E degrees [Au(2)(+)/Au(2)] < or = -1.85 V vs SSCE).

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