Bis Groups Research Articles

Synthesis, Characterization, and Optoelectronic Properties of a Novel Polyfluorene/Poly(p-Phenylenevinylene) Copolymer

A novel conjugated polyfluorene/poly(p-phenylenevinylene) copolymer containing the pendant bis(4-alkoxyphenyl) groups in the C-9 position of every alternating fluorene unit has been synthesized and well structurally characterized. The photoluminescence spectrum of this polymer exhibits strong concentration and excitation wavelength dependence in solution. The excited triplet-state maximum of polymer occurs in the region of 460−540 nm with a lifetime of 65.8 μs. This copolymer displays a minor positive nonlinear absorption at the focus of the laser irradiation, suggesting possible reverse saturable absorption. The stable electroluminescent spectrum of the polymer light-emitting diode device based on this copolymer (device configuration, indium−tin oxide/Au/copolymer/LiF/Al) was obtained with a peak wavelength of 515 nm. The bright-green emission observed over the whole active area of the copolymer closely resembles the photoluminescence of the most concentrated solution (0.5 M) used. This suggests that cha...

Effects of Bispectral Index Monitoring on Recovery from Surgical Anesthesia in 1,580 Inpatients from an Academic Medical Center

The purpose of this study was to determine whether monitoring Bispectral Index (BIS) would affect recovery parameters in patients undergoing inpatient surgery. Anesthesia providers (n = 69) were randomly assigned to one of two groups, a BIS or non-BIS control group. A randomized crossover design was used, with reassignment at monthly intervals for 7 months. Duration of time in the postanesthesia care unit, time from the end of surgery to leaving the operating room, and incidence of delayed recovery (> 50 min in recovery) were compared in patients treated intraoperatively with or without BIS monitoring. Data were analyzed by analysis of variance, unpaired t test, or chi-square test as appropriate. One thousand five hundred eighty patients in an academic medical center were studied. The mean BIS in the monitored group was 47. No differences were found in recovery parameters between the BIS-monitored group and the control group when comparisons were made using all subjects or when data were analyzed within anesthetic subgroups stratified by anesthetic agent or duration of anesthesia. There were some small reductions in the intraoperative concentration of sevoflurane (but not isoflurane). The use of BIS monitoring for inpatients undergoing a wide variety of surgical procedures in an academic medical center had some minor effects on intraoperative anesthetic use but had no impact on recovery parameters.

Postoperative Nausea and Vomiting does not Related to the Consumption of Sevoflurane under Control of Anesthetic Depth by Bispectral Index Monitoring

Background: BIS monitoring has been found to decrease the requirements for volatile anesthetics and to improve recovery. We wanted to assess the effect of BIS monitoring on intraoperative sevoflurane consumption, early recovery profile, and on postoperative nausea and vomiting. Methods: Forty ASA class 1 or 2 female patients undergoing mastectomy or thyroidectomy were studied. General anesthesia was induced with propofol (2.0 mg/kg) and fentanyl (/kg), and maintained with 50% nitrous oxide-oxygen and sevoflurane inhalation. In the control group, sevoflurane was administered according to standard clinical practice. In the BIS group, sevoflurane was titrated to maintain a BIS value between 40 and 60 during surgery and of more than 65 during the last 15 minutes prior to the end of surgery. Sevoflurane consumption was measured. Time to response, time to self respiration, time to extubation, and time to orientation were recorded. Postoperative nausea and vomiting were evaluated by incidence and by using a visual analogue scale (VAS). Results: Sevoflurane consumption in the BIS group was 30.4% lower than in the control group (P ＜ 0.05). All recovery times were significantly shorter in the BIS group than in the control group (P ＜ 0.05), but, no differences in postoperative nausea and vomiting were observed between the groups. Conclusions: BIS monitoring decreased and sevoflurane consumption and promoted early recovery. But BIS monitoring did not decrease postoperative nausea and vomiting.

Propene Polymerization with Bis(phenoxy–imine) Group 4 Transition Metal Complexes

Abstract Olefin polymerizations with group 4 transition metal complexes having two phenoxy–imine ligands (FI Catalysts) are reviewed with an emphasis on the characteristics and mechanisms of propene polymerization. The structures and properties of FI Catalysts can be easily modified by changing phenoxy–imine ligand structures. Such catalysts can be synthesized straightforwardly from readily available chemicals. An enormous library of FI Catalysts can be built up by combining a group 4 metal center and a variety of cocatalysts. The diversified library makes FI Catalysts so versatile that polyolefins with desired properties (molecular weight, molecular weight distribution, chain-end structure, tacticity, and so on) can be obtained sometimes predictably, by selecting the appropriate combination of ligand, metal, and cocatalyst. In propene polymerization, it remains a challenge to control the stereo- and regiochemistry of monomer enchainment in order to obtain commercially valuable products. FI Catalysts can produce syndiotactic and isotactic polypropene by Ti–FI catalysts/MAO and Zr– and Hf–FI catalysts/iBu3Al/Ph3CB(C6F5)4, respectively. Because of the well-defined and tunable nature of the catalysts, the coordination environment around the metal center can be controlled by the ligand structures to achieve extremely high stereoregularities, comparable to those of heterogeneous Ziegler–Natta catalysts and metallocene catalysts. These syndio- and isospecific FI Catalysts have contrasting reaction mechanisms, i.e., the syndiospecific polymerization is mediated via 2,1-insertion under chain-end control, while isospecificity arises from 1,2-insertion and a site control mechanism. The observed syndiospecificity can originate from the inherent fluxionality of FI Catalysts between configurational isomers.

Impact of Bispectral Index Monitoring on Stress Response and Propofol Consumption in Patients Undergoing Coronary Artery Bypass Surgery

Bispectral Index (BIS)-titrated administration allows a reduction of propofol infusion rates in patients undergoing surgery. Resulting differences in anesthetic depth might affect the stress response to surgery involving neural circuitry not reflected in the electroencephalogram. Forty patients scheduled to undergo elective coronary artery bypass grafting receiving a background infusion of remifentanil (0.3 microg . kg . min) were anesthetized with intravenous propofol delivered by target-controlled infusion according to the Marsh pharmacokinetic model under BIS monitoring. In a randomized, prospective design, 20 patients received propofol at a target concentration of 3 microg/ml, whereas in 20 patients propofol was titrated to maintain a BIS value of 40-50. Plasma concentrations of propofol (by means of gas chromatography-mass spectrometry), epinephrine, norepinephrine (by means of high-pressure liquid chromatography), cortisol (by means of radioimmunoassay), and interleukins 6 and 10 (by means of enzyme-linked immunosorbent assay) were measured repeatedly throughout surgery. BIS monitoring allowed a 30% reduction of propofol infusion rates and a similar decrease in plasma propofol concentrations in the BIS group without affecting the stress response to surgery for the group mean. None of the patients reported awareness during a standardized interview. Interestingly, propofol-remifentanil anesthesia blunted the release of epinephrine and cortisol to bypass surgery completely even when the propofol infusion rate was reduced according to BIS values. Total intravenous anesthesia using propofol-remifentanil effectively attenuates the neurohumoral stress response to coronary bypass surgery involving cardiopulmonary bypass. Titration of propofol using BIS allows for significant reduction of propofol consumption, with only minor effects on stress response under these conditions.

“Living” Propene Polymerization with Bis(phenoxyimine) Group 4 Metal Catalysts: New Strategies and Old Concepts

Bis(phenoxyimine)Ti catalysts with ortho-F-substituted phenyl rings on the N can be “living” propene polymerization catalysts. On the basis of DFT calculations, it has been proposed that the “living” behavior originates from an unprecedented attractive interaction between the said ortho-F atoms and a β-H of the growing polymer chain, which would render the latter less prone to be transferred to the metal (or to the monomer). In this paper, we report on a thorough full-QM and combined QM/MM investigation of representative model catalysts, demonstrating that the key factor is instead the repulsive nonbonded contact of the F-substituted rings with the growing polymer chain and an incoming propene molecule, which destabilizes the sterically demanding six-center transition structure for chain transfer to the monomer. A conceptually similar substituent effect has been reported before for several metallocene and non-metallocene catalysts; in the present case, though, this is partly alleviated by a weak attractive interaction between the ortho-F and a close-in-space α-H of the growing chain.

Bispectral index monitoring to prevent awareness during anaesthesia: The B-aware randomised controlled trial

Summary Background Awareness is an uncommon complication of anaesthesia, affecting 0·1–0·2% of all surgical patients. Bispectral index (BIS) monitoring measures the depth of anaesthesia and facilitates anaesthetic titration. In this trial we determined whether BIS-guided anaesthesia reduced the incidence of awareness during surgery in adults. Methods We did a prospective, randomised, double-blind, multicentre trial. Adult patients at high risk of awareness were randomly allocated to BIS-guided anaesthesia or routine care. Patients were assessed by a blinded observer for awareness at 2–6 h, 24–36 h, and 30 days after surgery. An independent committee, blinded to group identity, assessed every report of awareness. The primary outcome measure was confirmed awareness under anaesthesia at any time. Findings Of 2463 eligible and consenting patients, 1225 were assigned to the BIS group and 1238 to the routine care group. There were two reports of awareness in the BIS-guided group and 11 reports in the routine care group (p=0·22). BIS-guided anaesthesia reduced the risk of awareness by 82% (95% CI 17–98%). Interpretation BIS-guided anaesthesia reduces the risk of awareness in at-risk adult surgical patients undergoing relaxant general anaesthesia. With a cost of routine BIS monitoring at US$16 per use in Australia and a number needed to treat of 138, the cost of preventing one case of awareness in high-risk patients is about $2200.

Iron deficiency alters auditory recognition memory in newborn infants of diabetic mothers.

Infants of diabetic mothers (IDMs) are at risk for perinatal brain iron deficiency that may target the developing hippocampus. The objective of this study was to evaluate hippocampally based recognition memory and infant development in IDMs with suspected brain iron deficiency (BID; cord ferritin </=34 microg/L) compared with IDMs with sufficient brain iron stores (BIS; cord ferritin >34 microg/L) using event-related potentials (ERPs). ERPs assessed neonatal auditory cortical responses to sounds and auditory recognition memory in response to the mother's voice compared with a stranger's voice. Thirty-two newborn IDMs had cord serum ferritin concentrations and provided neonatal ERP data (n = 23) and/or blinded 1 y developmental assessments (n = 28). Auditory cortical responses to speech and nonspeech sounds were similar in the BID and BIS groups. In the maternal voice recognition paradigm, peak latencies were shorter in the BID group than in the BIS group. Infants in the BIS group displayed a significant negative slow wave for the strangers' voices compared with the mothers' voices, whereas the BID group did not. Higher cord ferritin concentrations were correlated with larger negative slow waves at the right temporal (T4) electrode site. At 1 y of age, motor development was slower in the BID group than in the BIS group. IDMs suspected to have BID demonstrated impaired neonatal auditory recognition memory and lower psychomotor developmental scores at 1 y of age than IDMs with BIS. These impairments map onto areas of the developing brain known to be vulnerable to iron deficiency.

Observation and identification of the catalytically active species of bis(phenoxy‐imine) group 4 transition metal complexes for olefin polymerization using 1H NMR spectroscopy

AbstractSolution structures of bis(phenoxy‐imine) group 4 transition metal complexes (FI Catalysts) were investigated using 1H NMR spectroscopy. At least two isomers exist in equilibrium for FI Catalysts precursors, bis[N‐(3‐tert‐butylsalicylidene)anilinato]zirconium(IV) dichloride (1), and bis[N‐(3,5‐dicumylsalicylidene)anilinato]zirconium(IV) dichloride (2), while bis[N‐(3‐tert‐butylsalicylidene)‐2,3,4,5,6‐pentafluoroanilinato]titanium(IV) dichloride (3) exhibits only one isomer under the conditions examined. Upon activation with MAO, all FI Catalysts (1‐3) generate two species at ambient temperature judging from some key signals in the 1H NMR. When temperature is raised (up to 75°C), one species (1a‐3a) converts irreversibly to the other species (1b‐3b). The resulting species, 1b‐3b, are stereochemically rigid, in contrast to precursors 1 and 2. Species 3b, derived from a living FI Catalyst, exhibited virtually no reactivity toward olefin insertion. The imine protons of species 1b‐3b are temperature and solvent polarity sensitive. Two possibilities are proposed for the assignment of species 1b‐3b, i) heterobinuclear complexes of group 4 metal and alkylaluminum with methyl and/or chlorine as bridging groups and ii) phenoxy‐imine ligated aluminum complexes whose ligands are transferred from the group 4 metal. The latter is more probable from the separate synthesis of LAlMe2 (L: phenoxy‐imine ligand). When 3 was activated with MAO in the presence of olefins, a new imine signal was observed. This species (3c for ethylene and 3d for propylene) is thermally more robust than 3a toward transformation to 3b and assignable to the living propagating species.

Bispectral index monitoring to prevent awareness during anaesthesia: the B-Aware randomised controlled trial

Awareness is an uncommon complication of anaesthesia, affecting 0.1-0.2% of all surgical patients. Bispectral index (BIS) monitoring measures the depth of anaesthesia and facilitates anaesthetic titration. In this trial we determined whether BIS-guided anaesthesia reduced the incidence of awareness during surgery in adults. We did a prospective, randomised, double-blind, multicentre trial. Adult patients at high risk of awareness were randomly allocated to BIS-guided anaesthesia or routine care. Patients were assessed by a blinded observer for awareness at 2-6 h, 24-36 h, and 30 days after surgery. An independent committee, blinded to group identity, assessed every report of awareness. The primary outcome measure was confirmed awareness under anaesthesia at any time. Of 2463 eligible and consenting patients, 1225 were assigned to the BIS group and 1238 to the routine care group. There were two reports of awareness in the BIS-guided group and 11 reports in the routine care group (p=0.022). BIS-guided anaesthesia reduced the risk of awareness by 82% (95% CI 17-98%). BIS-guided anaesthesia reduces the risk of awareness in at-risk adult surgical patients undergoing relaxant general anaesthesia. With a cost of routine BIS monitoring at US16 dollars per use in Australia and a number needed to treat of 138, the cost of preventing one case of awareness in high-risk patients is about 2200 dollars.

Development of FI Catalyst Systems and Their Applications to New Polyolefin‐Based Materials

AbstractFor Abstract see ChemInform Abstract in Full Text.

Hybrid Cyclic Dimers of Divacant Heteropolyanions: Synthesis, Mass Spectrometry (MALDI‐TOF and ESI‐MS) and NMR Multinuclear Characterisation

AbstractIn the field of organic‐inorganic hybrid composites, functionalized polyoxometalates constitute a special class of inorganic nanobuilding blocks (NBBs). This study represents a first approach related to the formation of new oligomeric hybrid species based on the reaction of bis(electrophilic) groups with a divacant heteropolyanion as the NBB. Bis(phosphonates) such as para‐H2O3PCH2(C6H4)nCH2PO3H2 (n = 1 or 2) have been treated with the divacant heteropolyanion [γ‐SiW10O36]8− to form the hybrid cyclic dimer [H2{(SiW10O36)(O=PCH2(C6H4)nCH2P=O)}2]6−. MALDI‐TOF and ESI mass spectrometry have been used as essential analytical techniques for the characterization of such composite systems. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2004)

New High-Performance Catalysts Developed at Mitsui Chemicals for Polyolefins and Organic Synthesis

This contribution reports Mitsui's R&D activities in the field of catalysis technology focusing on molecular catalysts. Examples of the high-performance molecular catalysts developed at Mitsui include bis(phenoxy-imine) group 4 transition metal complex catalysts (FI Catalysts), phosphazene catalysts (PZN catalysts) and b(beta)-ketoiminato Co(II) complex catalysts. Many of the materials stemming from these catalysts were either difficult or impossible to prepare using conventional catalysts.

Amidate Complexes of Titanium and Zirconium: A New Class of Tunable Precatalysts for the Hydroamination of Alkynes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Correlation of AEP, BIS and OAA/S Scores Under Stepwise Sedation Using Propofol TCI in Orthopedic Patients Undergoing Total Knee Replacement Arthroplasty Under Spinal Anesthesia

Background: We performed a prospective, randomized study to investigate the relations between BIS (bispectral index, monitor), AAI (mid-latency AEP, A-line ARX index) and depth of sedation, and assessed two different memory functions at OAA/S score 2 under spinal anesthesia. Methods: 44 ASA physical status 1-2 patients, scheduled for elective total knee replacement arthroplasty were randomly allocated to either the BIS group (22) or the AEP group (22). Under spinal anesthesia, patients were sedated with propofol TCI to OAA/S score 2. BIS and AAI at each OAA/S score were measured and patients were maintained at an OAA/S score 2. A specific picture was shown during the operation. At PACU, an interview was done to determine whether patients recalled specific picture (picture recall) or any intra-operative noises or scenes (op recall). Results: BIS decreased as OAA/S score reduced from 5 to 2 (P

Separation of Optically Active Ethynylsilane Derivatives and Their Polymerization by Transition-Metal Catalysts

Optically pure (-)-(4-bromophenyl)ethynylmethyl(1-naphthyllsilane [(-)-1],(-)-1,2-diethy-nyl-1,2-dimethyl-1,2-di(1-naphthyl)disilane [(-)-2], and (+)-1,2-diethynyl-1,2-dimethyl-1,2-diphenyldisilane [(+)-3] were separated by a chromatographic technique on an optically active stationary phase. Polymerization via Heck reaction or dimerization of bis(ethynyl) groups of these compounds gave optically active polymers. The structures of the polymers were characterized by 1 H, 13 C, and 29 Si NMR spectroscopies. Poly(1) and poly(2) have regular chemical structure. In poly(3), (E)-ene-yne is mixed with (E)-ene-(E)-ene and yne-yne structures. All the polymers are considered stereoregular concerning the configuration of the silicon atoms. The optical properties in solution were measured. Although the electronic absorption and fluorescence spectra of optically active polymers did not change compared with those of racemic polymers, the circular dichroism spectra showed a negative Cotton effect.

Dyeing of nylon 6 and silk fabrics with a model disulphide bis(ethylsulphone) reactive disperse dye

The synthesis of a new reactive disperse dye containing the disulphide bis(ethylsulphone) group is described. The dye has been applied to nylon 6 and silk fabrics at a variety of pH and temperature conditions. Optimum dye exhaustion and fixation were achieved at pH 8 and 130 °C. The results of dyeings on both substrates indicate that the model disulphide bis(ethylsulphone) reactive disperse dye shows a higher degree of exhaustion and fixation on silk than on nylon 6. The fastness and levelling properties on both fabrics were good.

Molecular switch triggered by solvent polarity: synthesis, Acid-base behavior, alkali metal ion complexation, and crystal structure.

The synthesis and characterization of the new tetraazamacrocycle L, bearing two 1,1'-bis(2-phenol) groups as side-arms, is reported. The basicity behavior and the binding properties of L toward alkali metal ions were determined by means of potentiometric measurements in ethanol/water 50:50 (v/v) solution (298.1+/-0.1 K, I=0.15 mol dm(-3)). The anionic H(-1)L(-) species can be obtained in strong alkaline solution, indicating that not all of the acidic protons of L can be removed under the experimental conditions used. This species behaves as a tetraprotic base (log K(1)=11.22, log K(2)=9.45, log K(3)=7.07, log K(4)=5.08), and binds alkali metal ions to form neutral [MH(-1)L] complexes with the following stability constants: log K(Li)=3.92, log K(Na)=3.54, log K(K)=3.29, log K(Cs)=3.53. The arrangement of the acidic protons in the H(-1)L(-) species depends on the polarity of the solvents used, and at least one proton switches from the amine moiety to the aromatic part upon decreasing the polarity of the solvent. In this way two different binding areas, modulated by the polarity of solvents, are possible in L. One area is preferred by alkali metal ions in polar solvents, the second one is preferred in solvents with low polarity. Thus, the metal ion can switch from one location to the other in the ligand, modulated by the polarity of the environment. A strong hydrogen-bonding network should preorganize the ligand for coordination, as confirmed by MD simulations. The crystal structure of the [Na(H(-1)L)].CH(3)CN complex (space group P2(1)/c, a=12.805(1), b=20.205(3), c=14.170(2) A, beta=100.77(1) degrees, V=3601.6(8) A(3), Z=4, R=0.0430, wR2=0.1181), obtained using CH(2)Cl(2)/CH(3)CN as mixed solvent, supports this last aspect and shows one of the proposed binding areas.

Syntheses and crystal structures of bis(4-dimethylaminopyridine) group 12 trifluoroacetates — M(OCOCF 3) 2·2DMAP (M=Zn, Cd, Hg)

Bis(4-dimethylaminopyridine) group 12 trifluoroacetates—M(OCOCF 3) 2·2DMAP (M=Zn, Cd, Hg) were prepared in quantitative yields from the anhydrous metal trifluoroacetates and DMAP. All compounds crystallize in the triclinic space group P 1 ̄ (no. 2) with two molecules per unit cell. While Zn(OCOCF 3) 2·2DMAP is built up by well-separated tetrahedral units exhibiting strongly covalent ZnO bonds to monodentate trifluoroactate groups, Cd(OCOCF 3) 2·2DMAP and Hg(OCOCF 3) 2·2DMAP form dimeric units. The metal centers are distorted octahedrally surrounded by two axial DMAP ligands, two ionic bridging and one chelating trifluoroacetate group.

The Usefulness of the Bispectral Index during Propofol and Fentanyl Anesthesia for Coronary Bypass Surgery under Cardiopulmonary Bypass

Background: The incidence of intraoperative awareness is known to be high in cardiac surgery using cardiopulmaonary bypass, and there is a tendency to use more anesthetics to maintain anesthesia without recall. We investigated the usefulness of the bispectral index monitor in reducing the amount of anesthetics without intraoperative awareness. Methods: Forty patients scheduled for elective coronary artery bypass graft surgery under cardiopulmonary bypass were randomly allocated into two groups. In the control group, systemic blood pressure was a main indicator to contol the infusion rate of propofol and fentanyl. Infusion rate of propofol and fentanyl were controlled by the bispectral index in the BIS group. A postanesthetic interview relating to intraoperative awareness was performed on the second postoperative day by a research assistant. Results: The average flow rate of propofol (control group;0.137 0.012 mg/kg/min, BIS group;0.110 0.003 mg/kg/min, P ＜ 0.01) and fentanyl (control group;6.485 0.413/kg/h, BIS group;4.321 0.5/kg/h, P ＜ 0.01) were significantly different between groups. The postoperative extubation time was 6.8 1.9 h in the control group and 5.3 2.3 h in the BIS group (P ＜ 0.05). The average BIS was 43.1 5.6. No subjects showed positive results in the intraoperative awareness test. Conclusions: Intraoperative monitoring of the bispectral index in patients undergoing cardiopulmonary bypass for coronary bypass surgery reduced requirement of anesthetics without intraoperative awareness.