Studies on the Complexes of N,N′-Bis[o-(diphenylphosphino)benzylidene]ethylenediamine with Transition Metal Ions

The thermodynamic parameters for the interaction of Cu²⁺, Ni²⁺, Co²⁺, Cd²⁺, andAg⁺ with the new title ligand have been determined by titration calorimetry in 50% THF–methanol (V/V) at 25 °C.Ag⁺ exhibited remarkably higher complexation selectivity.Ag⁺ and several transition metal ions have been transportedusing this ligand as carrier in a bulk liquid membrane. CompetitiveAg⁺–M²⁺ transport studies have also beencarried out for the same system. In this membrane transport study, high transport of Ag⁺ was observed in both single and competitiveAg⁺–M²⁺ transport studies. The complexformation of N,N-bis[o-(diphenylphosphino)benzylidene]ethylenediamine (P₂N₂) with silver,[Ag(P₂N₂)] (NO₃), (1) is reported. Complex 1 has been characterized by X-ray crystallography. 1 ismonoclinic, space group P2_1/n (No. 14), with cell dimensionsa = 13.398(4) , b=12.577(5) , c = 21.521(4) , =100.14(2) , V = 3570(2) ³ and Z = 4.     

Anatase-Rutile Transition of Precipitated Titanium Oxide with Alcohol Rinsing

The effect of alcohol washing on the anatase-rutile transition of precipitated titanium oxide was investigated using X-ray powder diffraction, Fourier-transform IR spectroscopy, and thermogravimetry. Alcohol (butanol) rinsing accelerated the anatase-rutile transition of precipitated titanium oxide powder so that the onset temperature of transition decreased drastically from 800 degrees C for water-washed powder to 550 degrees C for alcohol-rinsed powder. Alternation of transition kinetics and mechanisms by rinsing media could be confirmed from the analysis of temperature and time dependence of rutile content. The attributability of the chemical state of anatase after crystallization, which contained H(2)O, OH, and organic residues, to the change of transition kinetics with alcohol rinsing will be discussed. Two mechanisms, the effect of residual organics and/or H(2)O(OH), could be suggested on the basis of analysis of the difference between chemical states of water-washed anatase and alcohol-rinsed powder. Copyright 2000 Academic Press.     

Experimental and theoretical study on the olefin metathesis of alkenyl Baylis-Hillman adducts using second-generation Grubbs catalyst

[reaction: see text] We have investigated the olefin metathesis from alkenyl Baylis-Hillman adducts using second-generation Grubbs catalyst. In the experiment, the ring-closing metathesis (RCM) product could not be found, while the cross-metathesis (CM) products were found. The computational studies provided consistent explanations for the experimental result. The most limiting factor for the RCM process using second-generation Grubbs catalyst is caused by the high strain and steric effect in the metallacyclobutane intermediates.     

Pd(II)-Catalyzed cyclogeneration of carbocations: subsequent rearrangement and trapping under oxidative conditions

A catalytic oxidative polycyclization reaction initiated by the carbocyclization of 1,5-dienes with Pd(II) is reported. Trapping of a putative carbocation with suitable functional groups (phenols, alkenes, alcohols, sulfonamide), or rearrangement protocols (Pinacol) yields poly-cyclic products in good yields and in excellent diastereoselectivities. Turnover of the intermediate Pd-C bond is via β-H elimination.     

Separation of carbon nanotubes by frit inlet asymmetrical flow field-flow fractionation

Flow field-flow fractionation (flow FFF), a separation technique for particles and macromolecules, has been used to separate carbon nanotubes (CNT). The carbon nanotube ropes that were purified from a raw carbon nanotube mixture by acidic reflux followed by cross-flow filtration using a hollow fiber module were cut into shorter lengths by sonication under a concentrated acid mixture. The cut carbon nanotubes were separated by using a modified flow FFF channel system, frit inlet asymmetrical flow FFF (FI AFIFFF) channel, which was useful in the continuous flow operation during injection and separation. Carbon nanotubes, before and after the cutting process, were clearly distinguished by their retention profiles. The narrow volume fractions of CNT collected during flow FFF runs were confirmed by field emission scanning electron microscopy and Raman spectroscopy. Experimentally, it was found that retention of carbon nanotubes in flow FFF was dependent on the use of surfactant for CNT dispersion and for the carrier solution in flow FFF. In this work, the use of flow FFF for the size differentiation of carbon nanotubes in the process of preparation or purification was demonstrated.     

Direct determination of estriol 3- and 16-glucuronides in pregnancy urine by column-switching liquid chromatography with electrospray tandem mass spectrometry

Using column-switching liquid chromatography/tandem mass spectrometry (LC-MS/MS), we developed an improved analytical method of urinary estriol glucuronides. This new method is derived predominantly from maternal and fetal precursors in pregnancy. We used in the following procedure: first, we filtered urine samples with a membrane filter. Next, we directly injected the 50 microL aliquot of urine samples onto a pre-column. Then, after activating the column-switching valve, we backflushed the loaded samples onto the C(18) analytical column. Urine samples can be assayed within 20 min without any sample preparation steps. We monitored separated estriol glucuronides by negative electrospray ionization (ESI) and selected-reaction monitoring (SRM). The calibration range of estriol-3-glucuronide (E3-3G) and estriol-16-glucuronide (E3-16G) was 0.1-20 microg/mL and the linearity of the method was 0.9984 for E3-3G and 0.9987 for E3-16G. The limits of detection at a signal-to-noise (S/N) ratio of 3 were 10 ng/mL (E3-3G) and 5 ng/mL (E3-16G). The analytical recovery was over 85% and, in general, inter-day and intra-day variability for precision and accuracy were less than 10%. When applied to a pregnancy urine sample to biomedical monitoring of the function of the maternal/fetal unit, the proposed method allowed rapid and sensitive screening for the detection of E3-3G and E3-16G.     

Association behavior of a nitrilotriacetic-acid-modified dye in a poly(vinyl alcohol) film containing Ni(II)-adsorbed gold nanoparticles.

The association behavior of the dyes 5(6)-carboxyfluorescein and nitrilotriacetic acid (NTA)-modified 5(6)-carboxyfluorescein (F-NTA) in a poly(vinyl alcohol) (PVA) film and in a PVA film containing metal nanoparticles is investigated. Well-dispersed gold nanoparticles (AuNps) and Ni(II)-adsorbed AuNps are formed in the PVA film using in situ photochemical fabrication method. 5(6)-carboxyfluorescein and F-NTA are doped into the films. The F-NTA forms an H-aggregate in the PVA film containing Ni(II)-adsorbed AuNps. It is suggested that the interaction between NTA and Ni(II) adsorbed on the AuNps promotes the formation of the H-aggregate.     

In situ Fe K-edge X-ray absorption fine structure of a nitrosyl adduct of iron phthalocyanine irreversibly adsorbed on a high area carbon electrode in an acidic electrolyte

Key aspects of the microenvironment surrounding the Fe center in the nitrosyl adduct of iron phthalocyanine, [Fe(Pc)(NO)], have been elucidated from the analysis of the Fe K-edge extended X-ray absorption fine structure (EXAFS) of the material adsorbed on the surface of a high area carbon electrode recorded in situ, in 0.5 M H(2)SO(4). Statistical best fits to the EXAFS data place the Fe center in a five-coordinated square pyramidal configuration shifted away from the Pc plane toward the axially bound NO bent at an angle of ca. 40 degrees with respect to the normal to the Pc plane. This environment is analogous to that of Fe in the nitrosyl adduct of crystalline [Fe(TPP)], where TPP = meso-tetraphenylporphyrinato(2-), determined from X-ray diffraction.     

Photochemistry of 2-Allyl-3-oxo-2,3-dihydro-1H-pyrrole-2-carboxyalates

On acetone-sensitized irradiation the title compounds 3a–c are converted to 2-allyl-3-hydroxy-1H-pyrrole-2-carboxylates 4 in reasonable yields.