Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 18 de 18
Filtrar
Mais filtros








Base de dados
Intervalo de ano de publicação
1.
Mil Med ; 185(9-10): e1590-e1595, 2020 09 18.
Artigo em Inglês | MEDLINE | ID: mdl-32495838

RESUMO

INTRODUCTION: Despite an increasing number of female service members, incidence rates of gynecologic cancers (other than cervical cancer) have not been previously documented in the U.S. active duty military population. This study sought to determine the incidence rates of all gynecologic, including peritoneal, malignancies in the U.S. Active Duty population compared to the general US population as reported in the Surveillance, Epidemiology, and End Results Program database. MATERIALS AND METHODS: Gynecologic cancers diagnosed in U.S. Active Duty women aged 20-59 between 2004 and 2013 were retrospectively ascertained. Cancer cases were identified in both the Automated Central Tumor Registry and the Military Health System Data Repository. All cases in Automated Central Tumor Registry plus cases recorded in Military Health System Data Repository, but not duplicative of Automated Central Tumor Registry cases, were included. Age-specific and age-adjusted incidence rates were calculated in military and Surveillance, Epidemiology, and End Results cases. RESULTS: In U.S. Active Duty women, 327 incident cases of gynecologic cancer were identified. There were 110 cases of cervical cancer, 40 cases of endometrial cancer, 152 cases of ovarian cancer, and 25 other gynecologic malignancies. Of the 327 cases, 154 were ascertained from the Automated Central Tumor Registry database and the remainder from Military Health System Data Repository claims data. The age-adjusted rate of all gynecologic cancers for U.S. Active Duty women was 49.17 per 105 (95%CI 37.58, 65.12), while the age-adjusted rate for Surveillance, Epidemiology, and End Results -18 was 42.09 per 105 (95%CI 41.83, 42.35). The kappa coefficient assessing the overlap between the data sources was -0.1937. Though insufficient in numbers for statistical analysis, the observed proportion of ovarian to cervical cancer cases in active duty women < 45 years of age was substantially greater than in the general population. CONCLUSIONS: U.S. Active Duty women exhibited a similar age-adjusted rate of gynecologic cancer as the general US population. There was suboptimal overlap between the Automated Central Tumor Registry and Military Health System Data Repository databases, indicating the necessity of using both databases in order to obtain reliable data in the active duty population. This study is the current best estimate of a baseline rate of gynecologic cancer in U.S. active duty military women. This rate might change over time as women's roles and exposures in recent and future military conflicts evolve.


Assuntos
Neoplasias dos Genitais Femininos , Militares , Adulto , Feminino , Neoplasias dos Genitais Femininos/epidemiologia , Humanos , Incidência , Pessoa de Meia-Idade , Sistema de Registros , Estudos Retrospectivos , Estados Unidos/epidemiologia , Adulto Jovem
2.
J Patient Saf ; 16(4): 255-258, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32217934

RESUMO

OBJECTIVES: The aim of the study was to compare retained surgical item (RSI) rates for 137 Veterans Health Administration Surgery Programs with and without surgical count technology and the root cause analysis (RCA) for soft good RSI events between October 1, 2009 and December 31, 2016. A 2017 survey identified 46 programs to have independently acquired surgical count technology. METHODS: Retained surgical item rates were calculated by the sum of events (sharp, soft good, instrument) divided by the total procedures performed. The RCAs for RSI events were analyzed using codebooks for procedure type/location and root cause characterization. RESULTS: One hundred twenty-four RSI events occurred in 2,964,472 procedures for an overall RSI rate of 1/23,908 procedures. The RSI rates for 46 programs with surgical count technology were significantly higher in comparison with 91 programs without a surgical count technology system (1/18,221 versus 1/30,593, P = 0.0026). The RSI rates before and after acquiring the surgical count technology were not significantly different (1/17,508 versus 1/18,673, P = 0.8015). Root cause analyses for 42 soft good RSI events identified multiple associated disciplines (general surgery 26, urology 5, cardiac 4, neurosurgery 3, vascular 2, thoracic 1, gynecology 1) and locations (abdomen 26, thorax 7, retroperitoneal 4, paraspinal 2, extremity 1, pelvis 1, and head/neck 1). Human factors (n = 24), failure of policy/procedure (n = 21), and communication (n = 19) accounted for 64 (65%) of the 98 root causes identified. CONCLUSIONS: Acquisition of surgical count technology did not significantly improve RSI rates. Soft good RSI events are associated with multiple disciplines and locations and the following dominant root causes: human factors, failure to follow policy/procedure, and communication.


Assuntos
Corpos Estranhos/epidemiologia , Saúde dos Veteranos , Humanos , Tecnologia
3.
Fed Pract ; 36(4): 170-175, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31138969

RESUMO

Easily implemented ordering practices in the electronic health record increased the rate of guideline-concordant testing, decreased cost, and furthered the goal of high-value medical care.

4.
Malar J ; 12: 242, 2013 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-23855778

RESUMO

BACKGROUND: Ethiopia scaled up net distribution markedly starting in 2006. Information on expected net life under field conditions (physical durability and persistence of insecticidal activity) is needed to improve planning for net replacement. Standardization of physical durability assessment methods is lacking. METHODS: Permanet®2.0 long-lasting insecticidal bed nets (LLINs), available for distribution in early 2007, were collected from households at three time intervals. The number, size and location of holes were recorded for 189 nets used for three to six months from nine sites (2007) and 220 nets used for 14 to 20 months from 11 sites (2008). In 2009, a "finger/fist" sizing method classified holes in 200 nets used for 26 to 32 months from ten sites into small (<2 cm), medium (> = 2 to < =10 cm) and large (>10 cm) sizes. A proportionate hole index based on both hole number and area was derived from these size classifications. RESULTS: After three to six months, 54.5% (95% CI 47.1-61.7%) of 189 LLINs had at least one hole 0.5 cm (in the longest axis) or larger; mean holes per net was 4.4 (SD 8.4), median was 1.0 (Inter Quartile Range [IQR] 0-5) and median size was 1 cm (IQR 1-2). At 14 to 20 months, 85.5% (95% CI 80.1-89.8%) of 220 nets had at least one hole with mean 29.1 (SD 50.1) and median 12 (IQR 3-36.5) holes per net, and median size of 1 cm (IQR 1-2). At 26 to 32 months, 92.5% of 200 nets had at least one hole with a mean of 62.2 (SD 205.4) and median of 23 (IQR 6-55.5) holes per net. The mean hole index was 24.3, 169.1 and 352.8 at the three time periods respectively. Repairs were rarely observed. The majority of holes were in the lower half of the net walls. The proportion of nets in 'poor' condition (hole index >300) increased from 0% at three to six months to 30% at 26 to 32 months. CONCLUSIONS: Net damage began quickly: more than half the nets had holes by three to six months of use, with 40% of holes being larger than 2 cm. Holes continued to accumulate until 92.5% of nets had holes by 26 to 32 months of use. An almost complete lack of repairs shows the need for promoting proper use of nets and repairs, to increase LLIN longevity. Using the hole index, almost one third of the nets were classed as unusable and ineffective after two and a half years of potential use.


Assuntos
Mosquiteiros Tratados com Inseticida/estatística & dados numéricos , Controle de Mosquitos/instrumentação , Etiópia , Humanos , Malária/prevenção & controle
5.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 9): m1264-5, 2011 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-22064868

RESUMO

The crystal structure shows that the title compound, [Ni(2)(CH(3)CO(2))(C(27)H(24)Cl(3)N(4)O(3))(CH(4)O)(2)]·CH(3)OH·H(2)O, con-tains [Ni(2)L(OAc)(CH(3)OH)(2)] mol-ecules in the unit cell {H(3)L = 5-chloro-2-{1,3-bis[2-(5-chloro-2-oxidobenzylideneimino)-ethyl]imidazolidin-2-yl}phenolate} with water and methanol as solvates. The title compound is a neutral dinuclear compound, in which the L(3-) Schiff base acts as a hepta-dentate ligand, using each one of its N(2)O compartments to coordinate a nickel atom. The acetate anion bridges the two nickel atoms via one O while the distorted octahedral coordination sphere for each nickel atom is completed by a coordinated methanol ligand. One of the coordinated methanol ligands is involved in an intra-molecular hydrogen bond to the uncoordinated O atom of the bridging acetate ligand while the other forms a hydrogen bond with the methanol solvate. The solvate water mol-ecule forms strong hydrogen bonds to both terminal phenolato O atoms. The methanol solvate mol-ecule also forms a hydrogen bond with the water solvate mol-ecule.

6.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 10): m1381-2, 2011 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-22058698

RESUMO

The crystal structure of the title compound, [Ni(2)(C(27)H(24)Br(3)N(4)O(3))(CH(3)CO(2))(CH(3)OH)(H(2)O)]·2CH(3)OH·H(2)O contains [L(OAc){(CH(3)OH)Ni}{(H(2)O)Ni}] mol-ecules {H(3)L = 2-(5-bromo-2-hy-droxy-phen-yl)-1,3-bis-[4-(5-bromo-2-hy-droxy-phen-yl)-3-aza-but-3-en-yl]-1,3-imidazolidine} with additional water and two methanol solvent mol-ecules. In this instance, one of the two Ni atoms is coordinated to a water and the other to a methanol mol-ecule. The Ni-O and Ni-N distances, as well as the angles about the metal atoms, show quite regular octa-hedra around the central ions. The Ni-O(phenol)-Ni and Ni-O(acetate)-Ni angles are not similar [95.26 (13) and 97.34 (13)°, respectively], indicating that this subtle solvate exchange induces significant differences in the conformation adopted. The coordinated methanol ligand is involved in an intra-molecular hydrogen bond to the uncoordinated O atom of the bridging acetate ligand, while the coordinated water mol-ecule forms a hydrogen bond with the one of the methanol solvent mol-ecules. The water solvent mol-ecule forms strong hydrogen bonds to both phenolate O atoms. The remaining methanol solvent mol-ecule also forms a hydrogen bond with this solvent water mol-ecule.

7.
Acta Crystallogr Sect E Struct Rep Online ; 65(Pt 8): m1007-8, 2009 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-21583306

RESUMO

In the crystal of the dinuclear title compound, [Cu(2)(C(13)H(13)N(2)O)(2)(ClO(4))(2)]·2CH(3)CN, the two bridging perchlorate ions chelate to the two Cu(II) atoms in a µ-O:O' fashion on opposite sides of the equatorial plane. The Cu(II) ions display a distorted octa-hedral coordination geometry (in the usual 4 + 2 Jahn-Teller arrangement), each being coordinated by two O atoms from the two perchlorate ligands, and two N and O atoms from the reduced Schiff base ligand. The asymmetric unit contains two acetonitrile solvent mol-ecules. In the crystal structure, in addition to N-H⋯O hydrogen bonds, there are weak C-H⋯O inter-actions between the perchlorate O atoms and the reduced Schiff base ligand. C-H⋯N inter-actions are also present.

8.
Acta Crystallogr Sect E Struct Rep Online ; 65(Pt 9): m1121-2, 2009 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-21577463

RESUMO

The centrosymmetric binuclear complex, [Cu(2)(C(13)H(13)N(2)O)(2)(NCS)(2)], formed via phenolate oxygen bridges, involves the Cu(II) atoms in a distorted square-pyramidal coordination [τ = 0.197 (1)]. A Cu⋯Cu separation of 3.2281 (3) Šis observed. The in-plane Cu-O(phenolate) distance [1.9342 (8) Å] is shorter than the axial distance [2.252 (8) Å]. The Cu-N(amine) and Cu-N(py) distances are similar [2.0095 (10) and 2.0192 (10) Å, respectively]. The Cu-N(thio-cyanate) distance [1.9678 (11) Å] is in the range found for Cu-N distances in previously determined structures containing coordinated thio-cyanate anions. There is an inter-molecular hydrogen bond between the amine H atom and the S atom of a coordinated thio-cyanate anion.

9.
Acta Crystallogr Sect E Struct Rep Online ; 65(Pt 9): o2175, 2009 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-21577581

RESUMO

In the title salt, C(15)H(17)N(2) (+)·ClO(4) (-), the isoindoline N atom is protonated and an intra-molecular N-H⋯N hydrogen bond occurs. In the crystal, N-H⋯O and numerous weak C-H⋯O inter-actions occur between the cation and anion. The O atoms of the perchlorate anion are disordered over four sets of sites with occupancies of 0.438 (4), 0.270 (9), 0.155 (8) and 0.138 (5).

10.
J Am Chem Soc ; 130(37): 12246-7, 2008 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-18714999

RESUMO

A photosensitive caged copper complex has been prepared from a tetradentate ligand (H2cage) composed of two pyridyl-amide arms connected by a photoreactive nitrophenyl group. H2cage binds Cu2+ in aqueous solution with a stability constant (log beta) of 10.8, which corresponds to a KD of 16 pM at pH 7.4. The neutral Cu2+ complex, [Cu(OH2)(cage)], crystallizes as a distorted trigonal bipyramid coordinated by two amide and two pyridyl N atoms, with a water molecule bound in the trigonal plane. Photolysis with 350 nm UV light cleaves the ligand backbone to release photoproducts with significantly diminished affinity for Cu2+, thereby uncaging the metal ion. When coordinated as the caged complex, copper has diminished reactivity to produce hydroxyl radicals from Fenton-like reaction mixtures containing hydrogen peroxide and ascorbic acid. Postphotolysis, uncaged copper promotes hydroxyl radical formation under the same conditions. The strategy of caging copper is promising for applications where light could be used to trigger release of copper as a pro-oxidant to increase oxidative stress or as a tool to release copper intracellularly to study mechanisms of copper trafficking.


Assuntos
Amidas/química , Cobre/química , Compostos Organometálicos/química , Piridinas/química , Amidas/síntese química , Cristalografia por Raios X , Concentração de Íons de Hidrogênio , Cinética , Ligantes , Compostos Organometálicos/síntese química , Oxirredução , Fotólise , Piridinas/síntese química
11.
Inorg Chem ; 47(3): 1087-95, 2008 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-18163613

RESUMO

Cysteinyldopas are naturally occurring conjugates of cysteine and dopa (3,4-dihydroxy-l-phenylalanine) that are precursors to red pheomelanin pigments. Metal ions are known to influence pheomelanogenesis in vitro and may be regulatory factors in vivo. Cydo (3-[(2-amino-ethyl)sulfanyl]-4,6-di-tert-butylbenzene-1,2-diol) and CarboxyCydo (2-amino-3-(4,6-di-tert-butyl-2,3-dihydroxyphenylsulfanyl)-propionic acid) are model compounds of cysteinyldopa that retain its metal-binding functionalities but cannot polymerize due to the presence of blocking tert-butyl groups. Cydo reacts readily with zinc(II) acetate or nickel(II) acetate to form a cyclized 1,4-benzothiazine (zine) intermediate that undergoes ring contraction to form benzothiazole (zole) unless it is stabilized by coordination to a metal ion. The crystal structure of [Ni(zine)2] is reported. The acetate counteranion is required for the zinc-promoted reactivity, as neither zinc(II) sulfate nor zinc(II) chloride alone promotes the transformation. The counterion is less important for redox-active copper and iron, which both readily promote the oxidation of Cydo to zine and zole species; Cu(II) complexes of both zine and zole have been characterized by X-ray crystallography. In the case of CarboxyCydo, a 3-carboxy-1,4-benzothiazine intermediate decarboxylates to form [Cu(zine)2] under basic conditions, but in the absence of base forms a mixture of products that includes the carboxylated dimer 2,2'-bibenzothiazine (bi-zine). These products are consistent with species implicated in the pheomelanogenesis biosynthetic pathway and emphasize how metal ions, their counteranions, and reaction conditions can alter pheomelanin product distribution.


Assuntos
Cisteinildopa/química , Metais/química , Cristalografia por Raios X , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Espectrofotometria Infravermelho , Espectrofotometria Ultravioleta
12.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 2): m323, 2008 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-21201292

RESUMO

Each Cu atom in the dinuclear centrosymmetric title complex, [Cu(2)Br(2)(C(14)H(17)N(3))(2)](ClO(4))(2), is ligated in a distorted square-pyramidal geometry (τ = 0.31) by a tridentate bis-[2-(2-pyrid-yl)eth-yl]amine ligand, and by two bridging Br atoms. In addition, the dinuclear species is stabilized by two hydrogen-bonded perchlorate anions.

13.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 2): o377-8, 2008 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-21201408

RESUMO

The title compound, C(8)H(14)N(2) (2+)·C(12)H(8)N(2)O(8)P(-)·ClO(4) (-), was formed by the reaction of α,α-bis-m-xylenediamine and sodium bis-p-nitro-phenyl-phosphate in the presence of Zn(ClO(4))·6H(2)O in methanol solution. The two amine groups of the m-xylenediammonium ion are each protonated and each hydrogen-bonded to two O atoms of the phosphate anion, which acts as a 1,3-bridge. The ammonium groups are arranged matched face to face and each pair is doubly bridged by two perchlorate ions through hydrogen bonding. In addition, there are also weak C-H⋯O inter-actions. Both the N-H⋯O and C-H⋯O inter-actions are contained in a channel down the a axis. The perchlorate oxygen atoms are disordered over two positions with site occupancy factors of ca 0.7 and 0.3.

14.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 1): m233-4, 2007 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-21200577

RESUMO

In the title compound, [Cu(ClO(4))(2)(C(12)H(13)N(3))(C(2)H(3)N)], the Cu(II) atom is six-coordinate in a Jahn-Teller distorted octahedral geometry, with coordination by the tridentate chelating ligand, an acetonitrile mol-ecule, and two axial perchlorate anions. The tridentate ligand bis-(2-pyridylmeth-yl)amine chelates meridionally and equatorially while an acetonitrile mol-ecule is coordinated at the fourth equatorial site. The two perchlorate anions are disordered with site occupancy factors of 0.72/0.28. The amine H is involved in intra-molecular hydrogen bonding to the perchlorate O atoms and there are extensive but weak inter-molecular C-H⋯O inter-actions.

15.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 1): m74-5, 2007 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-21200643

RESUMO

The title compound, [Cu(C(6)H(8)N(2))(C(13)H(15)N(3))](ClO(4))(2), is a mixed ligand complex with the Cu(II) atom coordinated by (6-methyl-2-pyridylmeth-yl)(2-pyridylmeth-yl)amine, acting as a tridentate ligand, and 2-(2-amino-meth-yl)pyridine, as a bidentate ligand, leading to an N(5) square-pyramidal geometry. The amine H atoms are involved in hydrogen bonding to the perchlorate O atoms and there are extensive but weak inter-molecular C-H⋯O inter-actions in the crystal structure. The perchlorate ions are each disordered over two positions, with site occupancies of 0.601 (8):0.399 (8) and 0.659 (11):0.341 (11).

16.
Inorg Chem ; 45(16): 6102-4, 2006 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-16878910

RESUMO

A new cysteinyldopa model ligand Cydo {3-[(2-aminoethyl)sulfanyl]-4,6-di-tert-butylbenzene-1,2-diol} was prepared and its reactivity with Cu(II) explored. Under anaerobic conditions, tetranuclear [Cu4(Cydo)4] is isolated, but in the presence of O2, a benzothiazine intermediate accumulates that is trapped as the Cu(II) complex [Cu(zine)2]. Under slightly different reaction conditions, the benzothiazine further oxidizes to benzothiazole (zole). All three compounds were characterized by X-ray crystallography, and the reactions were monitored spectrophotometrically.


Assuntos
Derivados de Benzeno/química , Cobre/química , Cisteinildopa/análogos & derivados , Melaninas/química , Tiazinas/química , Derivados de Benzeno/síntese química , Cisteinildopa/síntese química , Ligantes , Tiazinas/síntese química
17.
Inorg Chem ; 45(7): 3023-33, 2006 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-16562958

RESUMO

The dinucleating ligand, 2,6-bis{[(2-(2-pyridyl)ethyl)(2-pyridylmethyl)-amino]-methyl}-4-methylphenol) (L1OH) reacts with Mn(ClO4)2.6H2O to form the dinuclear complex [Mn2(II,II)(L1O)(mu-OOCCH3)2]ClO4 (1). The electrolytic oxidation of 1 at 0.7 V (vs Ag/AgCl) produces the mixed valent complex [Mn2(II,III)(L1O)(mu-OOCCH3)2](ClO4)2 (1ox) quantitatively, while electrolysis at 0.20 V converts 1ox back to 1. X-ray crystallographic structures show that both 1 and 1ox are dinuclear complexes in which the two manganese ions are each in distorted octahedral coordination environments bridged by the phenoxo oxygen and two acetate ions. The structural changes that occur upon the oxidation 1 to 1ox suggest an extended pi-bonding system involving the phenoxo ring C-O(phenoxo)-Mn(II)-N(pyridyl) chain. In addition, as 1 is oxidized to 1ox, the rearrangements in the coordination sphere resulting from the oxidation of one Mn(II) ion to Mn(III) are transmitted via the bridging Mn-O(phenoxo) bonds and cause structural changes that render the site of the second manganese ion unfit for the +3 state and hence unstable to reduction. Thus the electrolytic oxidation of 1ox in acetonitrile at 1.20 V takes up slightly greater than 1 F of charge/mol of 1ox, but the starting complex, 1ox, is recovered, showing the instability of the Mn2(III,III) state that is formed with respect to reduction to 1ox. Variable-temperature magnetic susceptibility measurements of 1 and 1ox over the temperature range from 1.8 to 300 K can be modeled with magnetic coupling constants J = -4.3 and -4.1 cm(-1), respectively showing the weak antiferromagnetic coupling between the two manganese ions in each dinuclear complex, which is commonly observed among similar phenoxo- and bis-1,3-carboxylato-bridged dinuclear Mn2(II,II) and Mn2(II,III) complexes.


Assuntos
Manganês/química , Compostos Organometálicos/química , Cristalografia por Raios X , Eletroquímica , Ligantes , Magnetismo , Modelos Moleculares , Estrutura Molecular , Compostos Organometálicos/síntese química , Oxirredução , Temperatura
18.
Inorg Chem ; 42(6): 1857-67, 2003 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-12639118

RESUMO

The syntheses and structural, spectral, and electrochemical characterization of the dioxo-bridged dinuclear Mn(III) complexes [LMn(mo-O)(2)MnL](ClO(4))(2), of the tripodal ligands tris(6-methyl-2-pyridylmethyl)amine (L(1)) and bis(6-methyl-2-pyridylmethyl)(2-(2-pyridyl)ethyl)amine (L(2)), and the Mn(II) complex of bis(2-(2-pyridyl)ethyl)(6-methyl-2-pyridylmethyl)amine (L(3)) are described. Addition of aqueous H(2)O(2) to methanol solutions of the Mn(II) complexes of L(1) and L(2) produced green solutions in a fast reaction from which subsequently precipitated brown solids of the dioxo-bridged dinuclear complexes 1 and 2, respectively, which have the general formula [LMn(III)(mu-O)(2)Mn(III)L](ClO(4))(2). Addition of 30% aqueous H(2)O(2) to the methanol solution of the Mn(II) complex of L(3) ([Mn(II)L(3)(CH(3)CN)(H(2)O)](ClO(4))(2) (3)) showed a very sluggish change gradually precipitating an insoluble black gummy solid, but no dioxo-bridged manganese complex is produced. By contrast, the Mn(II) complex of the ligand bis(2-(2-pyridyl)ethyl)(2-pyridylmethyl)amine (L(3a)) has been reported to react with aqueous H(2)O(2) to form the dioxo-bridged Mn(III)Mn(IV) complex. In cyclic voltammetric experiments in acetonitrile solution, complex 1 shows two reversible peaks at E(1/2) = 0.87 and 1.70 V (vs Ag/AgCl) assigned to the Mn(III)(2) <--> Mn(III)Mn(IV) and the Mn(III)Mn(IV) <--> Mn(IV)(2) processes, respectively. Complex 2 also shows two reversible peaks, one at E(1/2) = 0.78 V and a second peak at E(1/2) = 1.58 V (vs Ag/AgCl) assigned to the Mn(III)(2) <--> Mn(III)Mn(IV) and Mn(III)Mn(IV) <--> Mn(IV)(2) redox processes, respectively. These potentials are the highest so far observed for the dioxo-bridged dinuclear manganese complexes of the type of tripodal ligands used here. The bulk electrolytic oxidation of complexes 1 and 2, at a controlled anodic potential of 1.98 V (vs Ag/AgCl), produced the green Mn(IV)(2) complexes that have been spectrally characterized. The Mn(II) complex of L(3) shows a quasi reversible peak at an anodic potential of E(p,a) of 1.96 V (vs Ag/AgCl) assigned to the oxidation Mn(II) to Mn(III) complex. It is about 0.17 V higher than the E(p,a) of the Mn(II) complex of L(3a). The higher oxidation potential is attributable to the steric effect of the methyl substituent at the 6-position of the pyridyl donor of L(3).

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA