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- Foundation fieldbus : from theory to practicePublication . Viegas, Vítor; Pereira, José Miguel Costa DiasThis paper describes the main characteristics of the Foundation Fieldbus (FF) technology considering both communication levels, namely H1 and H2, which have bit rates of 31.25 K and 100 Mbit/s, respectively. Several details about the physical layer, communication stack and user layer will be highlighted. Topics related with the configuration of instruments, as well as the design and implementation of supervision software, based on a LabVIEW interface, will be presented. A pilot plant that includes temperature, pressure, level and flow variables will be used to test and validate the capabilities of FF systems. Experimental results will be analyzed, their meaning discussed and the overall performance evaluated.
- Control of Neuromuscular Blockade in the Presence of Sensor FaultsPublication . Lemos, João M.; Magalhães, Hugo; Mendonça, Teresa; V. Dionísio, R.The problem of embedding sensor fault tolerance infeedback control of neuromuscular blockade is considered. Fortackling interruptions of feedback measurements, a structurebased upon Bayesian inference as well as a predictive filter is pro-posed. This algorithm is general and can be applied to differentsituations. Here, it is incorporated in an adaptive automatic systemfor feedback control of neuromuscular blockade using continuousinfusion of muscle relaxants. A significant contribution consistsin the experimental clinical testing of the algorithm in patientsundergoing surgery.
- Stability of Discrete Systems Controlled in the Presence ofIntermittent Sensor FaultsPublication . V. Dionísio, R.; Lemos, João M.
- Oxido-bis¬[chlorido(4,4'-di-tert-butyl-2,2'-bipyridine-2N,N')dioxido¬molybdenum(VI)] 0.2-hydratePublication . Gomes, A. C.; Fernandes, J. A.; Gamelas ou Carla A. Gamelas, Carla; Gonçalves, I. S.; Almeida-Paz, F. A.The title hydrate, [Mo2Cl2O5(C18H24N2)2]·0.2H2O, has been isolated as the oxidation product of [Mo(3-C3H5)Cl(CO)2(di-t-Bu-bipy)] (where di-t-Bu-bipy is 4,4'-di-tert-butyl-2,2'-bipyridine). A -oxide ligand bridges two similar MoCl(di-t-Bu-bipy)O2 units, having the terminal oxide ligands mutually cis, and the chloride and -oxide trans to each other. In the binuclear complex, the coordination geometries of the metal atoms can be described as highly distorted octahedra. Individual complexes co-crystallize with a partially occupied water molecule of crystallization (occupancy factor = 0.20; H atoms not located), with the crystal packing being mediated by the need to effectively fill the available space. A number of weak C-HO and C-HCl interactions are present.
- Chemoselective Sulfide and Sulfoxide Oxidations by CpMo(CO)3Cl/HOOR: a DFT Mechanistic Study. OrganometallicsPublication . Veiros, Luís; Gamelas ou Carla A. Gamelas, Carla; Calhorda, Maria José; Romão, CarlosThe mechanism of sulfide and sulfoxide oxidation with peroxides (ROOH, R = H, Me), catalyzed by Mo(VI) complexes, was investigated by means of DFT/PBE1PBE calculations. Two different catalytic systems were considered: the first is based on the dioxocyclopentadienyl (Cp) complex CpMoO2Cl (Cp = η5-C5H5), also active as a catalyst for olefin epoxidation, and the second based on MoO2Cl2. The most favorable mechanism in the Cp system is initiated by the O−H activation of the HOOR oxidant, which in the presence of CpMoO2Cl leads to formation of CpMoO(OH)(OOR)Cl. Although this is the active species for olefin epoxidation, an alternative pathway with lower energy is available. With the crucial H-bond assistance of another oxidant molecule, the oxoperoxo complex CpMoO(O2)Cl forms, with release of alcohol ROH as byproduct and a calculated energy barrier below 25 kcal mol−1. The mechanisms unveiled for sulfide to sulfoxide oxidation and for sulfoxide to sulfone oxidation are equivalent in their general features and follow outer-sphere mechanisms with S-nucleophilic attack from a free molecule of substrate (sulfide or sulfoxide) to the peroxide which is activated through Mo−O coordination. The MoO2Cl2 catalyst follows a similar course, calculated from MoO2Cl2(H2O)(H2O2). Again, explicit consideration of one molecule of solvent (water) proved essential to facilitate the H-transfer processes involved in the mechanism. The highest energy barrier calculated (ca. 25 kcal mol−1) corresponds to a H shift from the Oα to the Oβ atom of the coordinated H2O2 molecule, activating Oα for the oxidation reaction and preparing water (H2Oβ) as the future leaving group. The outer-sphere mechanism ends with coordination of the oxidation product.
- Indenyl ring slippage in crown thioether complexes [IndMo(CO)2L]+ and C–S activation of trithiacyclononane: Experimental and theoretical studiesPublication . Gamelas ou Carla A. Gamelas, Carla; Bandeira, Nuno; Pereira, Cláudia; Calhorda, Maria José; Herdtweck, Eberhardt; Machuqueiro, Miguel; Romão, Carlos; Veiros, LuísThe macrocycle 1,4,7-trithiacyclononane (ttcn) reacts with [(η5-Ind)Mo(CO)2(NCMe)2]+ (or [(η5-Ind)Mo(CO)2(κ2-dme)]+) to give [(η3-Ind)Mo(CO)2(κ3-ttcn)]+ as the BF4− salt (1), but its reaction with [(η5-Ind)Mo(CO)2(C3H6)(FBF3)] affords the C–S bond cleavage product [(η5-Ind)Mo(CO)(κ3-1,4,7-trithiaheptanate)]BF4 (6), which has been characterised by X-ray crystallography (Ind = C9H7, indenyl). In contrast to ttcn, the macrocycles 1,3,5-trithiane (tt) and 1,4,7,10-tetrathiacyclododecane (ttcd) fail to induce changes in the coordination mode of indenyl: tt and ttcd react with [(η5-Ind)Mo(CO)2(NCMe)2]+ (or [(η5-Ind)Mo(CO)2(κ2-dme)]+) to give [(η5-Ind)Mo(CO)2(κ2-tt)]+ (2), characterised by X-ray crystallography, and [(η5-Ind)Mo(CO)2(κ2-ttcd)]+ (3), respectively. The cyclopentadienyl (Cp = C5H5) analogues [(η5-CpMo(CO)2(κ2-tt)]+ (4) and [(η5-CpMo(CO)2(κ2-ttcn)]+ (5) have also been synthesised and 5 characterised by X-ray crystallography. DFT calculations showed that the η5-Ind/Cp coordination mode is always the most stable. However, a molecular dynamics study of the macrocycles conformations revealed that the major conformer of ttcn was a chair, which favoured κ3 coordination. As indenyl complexes undergo slippage with a small barrier (<10 kcal mol−1), the kinetically preferred species [(η3-Ind)Mo(CO)2(κ3-ttcn)]+ (1) is the observed one. The conversion to 6 proceeds stepwise, with loss of ethylene followed by loss of CO, as calculated by DFT, with a barrier of 38.7 kcal mol−1, consistent with the slow uncatalysed reaction.
- Chiral Cationic [Cp′Mo(CO)2(NCMe)]+ Species – Catalyst Precursors for Olefin Epoxidation with H2O2 and tert-Butyl HydroperoxidePublication . Reis, Patrícia; Gamelas ou Carla A. Gamelas, Carla; Brito, José; Saffon, Nathalie; Goméz, Montserrat; Royo, BeatrizA novel cyclopentadienyl ligand bearing a chiral oxazoline pendant group (Cpox) has been prepared. Its coordination to molybdenum and tungsten afforded optically pure (R)-CpoxM(η3-C3H5)(CO)2 (M = Mo, W) in which the pendant oxazoline fragment is not coordinated to the metal center. Reaction of (R)-CpoxMo(η3-C3H5)(CO)2 with tetrafluoroboric acid gives the bidentate η5-cyclopentadienyloxazoline complex [CpoxMo(CO)2(NCMe)]BF4 in which the oxazoline is coordinated through the N-atom to the molybdenum center. Their catalytic performance in the epoxidation of cis-cyclooctene, (R)-limonene, and trans-β-methylstyrene with H2O2 and tert-butyl hydroperoxide (TBHP) as oxidants has been studied. (R)-CpoxW(η3-C3H5)(CO)2 displayed high catalytic activity achieving quantitative conversion of cyclooctene epoxide in 2 h with H2O2. [CpoxMo(CO)2(NCMe)]+ has been shown to be an efficient catalyst with TBHP and H2O2, reaching quantitative conversions of the corresponding epoxide in 30 min and 11 h, respectively. ESI-MS studies of the reaction of [CpoxMo(CO)2(NCMe)]+ with H2O2 and TBHP revealed the in situ formation of the corresponding peroxido [CpoxMo(O2)O]+ and dioxido [CpoxMoO2]+ species, respectively. Further oxidation of these complexes resulted in the loss of the cyclopentadienyloxazoline ligand. Based on spin trap experiments, the involvement of both carbon- and oxygen-centred radicals in the olefin epoxidation catalyzed by [CpoxMo(CO)2(NCMe)]+ has been proved.
- Molybdenum(II) Diiodo-Tricarbonyl Complexes Containing Nitrogen Donor Ligands as Catalyst Precursors for the Epoxidation of Methyl OleatePublication . Gamelas ou Carla A. Gamelas, Carla; Neves, P.; Gomes, A. C.; Valente, A.; Romão, C.; Gonçalves, I.; Pillinger, M.The molybdenum(II) tricarbonyl complexes [Mo(CO)3I2L n ] (n = 1, L = 2,2′-bipyridine, 4,4′-di-tert-butyl-2,2′-bipyridine; n = 2, L = pyridine, 4-tert-butylpyridine) have been examined as catalyst precursors for the epoxidation of the biorenewable olefin methyl oleate with tert-butylhydroperoxide. In situ oxidative decarbonylation of the precursors gives highly active and selective molybdenum(VI) catalysts, which were identified as the one-dimensional molybdenum oxide/bipyridine polymer [MoO3(2,2′-bipyridine)], octanuclear [Mo8O24(4,4′-di-tert-butyl-2,2′-bipyridine)4], and the pyridinium β-octamolybdates (LH)4[Mo8O26] for L = pyridine or 4-tert-butylpyridine.
- Molybdenum(VI) Catalysts obtained from eta3-Allyl Dicarbonyl Precursors: Synthesis, Characterization and Catalytic Performance in Cyclooctene EpoxidationPublication . Gamelas ou Carla A. Gamelas, Carla; Gomes, A. C.; Bruno, S.; Almeida-Paz, F.; Valente, A.; Pillinger, M.; Romão, C.; Gonçalves, I.The oxidative decarbonylation of the η3-allyl dicarbonyl complexes [Mo(η3-C3H5)Cl(CO)2(L)] (L = 2,2′- bipyridine (bipy) (1), 4,4′-di-tert-butyl-2,2′-bipyridine (di-tBu-bipy) (2)) by reaction with aqueous tertbutylhydroperoxide (TBHP) or H2O2 gave the following compounds in good to excellent yields: the oxobridged dimers [MoO2Cl(L)]2O (L = bipy (3), di-tBu-bipy (6)) using TBHP(10 equiv.)/CH3CN/r.t.; the molybdenum oxide/bipyridine hybrid material {[MoO3(bipy)][MoO3(H2O)]}n (4) and the octanuclear complex [Mo8O24(di-tBu-bipy)4] (7) using TBHP(50 equiv.)/H2O/70 °C; the oxodiperoxo complexes MoO(O2)2(L) (L = bipy (5), di-tBu-bipy (8)) using H2O2(10 equiv.)/CH3CN/r.t. The structure of 7·x (solvent) (where solvent = CH2Cl2 and/or diethyl ether) was determined by single crystal X-ray diffraction. Despite possessing the same windmill-type complex as that described previously for 7·10CH2Cl2, the crystal structure of 7·x(solvent) is unique due to differences in the crystal packing. Compounds 1–8 were examined as catalysts or catalyst precursors for the epoxidation of cyclooctene using aqueous TBHP or H2O2 as oxidant at 55 or 70 °C. Reactions were performed without co-solvent or with the addition of water, ethanol or acetonitrile. Cyclooctene oxide was always the only reaction product. Solids recovered after 24 h reaction at 70 °C were identified by FT-IR spectroscopy as the hybrid 4 from (1,3–5)/TBHP, complex 5 from (1,3–5)/H2O2, and complex 8 from (2,6–8)/H2O2. With TBHP as oxidant, the highest epoxide yields (for 24 h reaction at 70 °C) were obtained using excess H2O as solvent (28–38% for 1,3–5; 87–98% for 2,6–8), while with H2O2 as oxidant, the highest epoxide yields were obtained using CH3CN as solvent (54–81% for 3–8).
- Isomerization of alfa-pinene oxide in the presence of indenyl allyl dicarbonyl molybdenum(II) and tungsten(II) complexesPublication . Bruno, S. M.; Gamelas ou Carla A. Gamelas, Carla; Gomes, A. C.; Valente, A.; Pillinger, M.; Romão, C.; Gonçalves, I.The indenyl complexes IndM(η3-C3H5)(CO)2 (M=Mo (1), W (2)), (IndMe)Mo(η3-C3H5)(CO)2 (3) and (IndSiMe3)Mo(η3-C3H5)(CO)2 (4) display catalytic activity for the isomerisation of α-pinene oxide. Conversion reached 97% after 3 h at 35 °C in the presence of 1 and 1,2-dichloroethane as solvent, giving campholenic aldehyde in 56% yield. Solvent polarity and basicity appear to affect the reaction rate. Whereas the type of substituent on the indenyl ligand does not appear to have a strong impact on catalytic performance, changing the metal centre from Mo (1) toW(2) gave a significantly more active catalyst.