Resonance Raman studies of beta-substituted porphyrin systems with unusual electronic absorption properties.

Zn(II) and Cu(II) porphyrins with beta-conjugated barbiturate functional groups have low-energy electronic transitions which are unusual in that there are two strong bands in the Soret region. Resonance excitation of the two bands shows that each has features characteristic of both the porphyrin and barbiturate groups, with some perturbation to these features caused by the interaction of the two chromophores. The resonance Raman (RR) spectrum (lambda(exc)=413.1 nm) of the 412 nm band shows two bands at 1722 and 1743 cm(-1) attributable to C==O stretches in the substituent. Changes in frequency of porphyrin core modes due to the differing metal centres are reproduced by density functional theory calculations. The Q band RR spectra show modes with anomalous polarization which may be attributed to A(2g) modes, however no overtone or combination bands are observed.     

Efficient synthesis of magnetic nanoparticle-Musa acuminata peel composite for the adsorption of anionic dye

The impregnation of magnetite (Mt) nanoparticle (NPs) onto Musa acuminata peel (MApe), to form a novel magnetic combo (MApe-Mt) for the adsorption of anionic bromophenol blue (BPB) was studied. The SEM, EDX, BET, XRD, FTIR and TGA were used to characterize the adsorbents. The FTIR showed that the OH and CO groups were the major sites for BPB uptake onto the adsorbent materials. The average Mt crystalline size on MApe-Mt was 21.13 nm. SEM analysis revealed that Mt NPs were agglomerated on the surface of the MApe biosorbent, with an average Mt diameter of 25.97 nm. After Mt impregnation, a decrease in BET surface area (14.89 to 3.80 m²/g) and an increase in pore diameter (2.25–3.11 nm), pore volume (0.0052–0.01418 cm³/g) and pH point of zero charge (6.4–7.2) was obtained. The presence of Pb(II) ions in solution significantly decreased the uptake of BPB onto both MApe (66.1–43.8%) and MApe-Mt (80.3–59.1%), compared to other competing ions (Zn(II), Cd(II), Ni(II)) in the solution. Isotherm modeling showed that the Freundlich model best fitted the adsorption data (R² > 0.994 and SSE < 0.0013). In addition, maximum monolayer uptake was enhanced from 6.04 to 8.12 mg/g after Mt impregnation. Kinetics were well described by the pseudo-first order and liquid film diffusion models. Thermodynamics revealed a physical, endothermic adsorption of BPB onto the adsorbents, with ΔH^o values of 15.87–16.49 kJ/mol, corroborated by high desorption (over 90%) of BPB from the loaded materials. The viability of the prepared adsorbents was also revealed in its reusability for BPB uptake.     

Concentration profiles of cocaine, pyrolytic methyl ecgonidine and thirteen metabolites in human blood and urine: determination by gas chromatography-mass spectrometry

When cocaine is smoked, a pyrolytic product, methyl ecgonidine (anhydroecgonine methyl ester), is also consumed with the cocaine. The amount of methyl ecgonidine formed depends on the pyrolytic conditions and composition of the illicit cocaine. This procedure describes detection of cocaine and 10 metabolites--cocaethylene, nor-cocaine, nor-cocaethylene, methyl ecgonine, ethyl ecgonine, benzoylecgonine, nor-benzoylecgonine, m-hydroxybenzoylecgonine, p-hydroxybenzoylecgonine and ecgonine--in blood and urine. In addition, the detection of pyrolytic methyl ecgonidine and three metabolites--ecgonidine (anhydroecgonine), ethyl ecgonidine (anhydroecgonine ethyl ester) and nor-ecgonidine (nor-anhydroecgonine)--are included. The newly described metabolites, ethyl ecgonidine and nor-ecgonidine, were synthesized and characterized by gas chromatography-mass spectrometry (GC-MS). All 15 compounds were extracted from 3 mL of blood or urine by solid-phase extraction and identified by a GC-MS method. The overall recoveries were 49% for methyl ecgonine, 35% for ethyl ecgonine, 29% for ecgonine and more than 83% for all other drugs. The limits of detection were between 0.5 and 4.0 ng/mL except for ecgonine, which was 16 ng/mL. Linearity for each analyte was established and in all cases correlation coefficients were 0.9985-1.0000. The procedure was applied to examine the concentration profiles of analytes of interest in post-mortem (PM) blood and urine, and in urine collected from living individuals (LV). These specimens previously were shown to be positive for the cocaine metabolite, benzoylecgonine. Ecgonidine, the major metabolite of methyl ecgonidine, was present in 77% of PM and 88% of the LV specimens, indicating smoking as the major route of cocaine administration. The new pyrolytic metabolites, ethyl ecgonidine and nor-ecgonidine, were present in smaller amounts. The urine concentrations of nor-ecgonidine were 0-163 ng/mL in LV and 0-75 ng/mL in PM specimens. Ethyl ecgonidine was found only in PM urine at concentrations 0-39 ng/mL. Ethanol-related cocaine metabolites, ethyl ecgonine or cocaethylene, were present in 69% of PM and 53% of cocaine-positive LV specimens, implying alcohol consumption with cocaine use. The four major metabolites of cocaine--benzoylecgonine, ecgonine, nor-benzoylecgonine and methyl ecgonine--constituted approximately 88 and 97% of all metabolites in PM and LV specimens, respectively. The concentrations of nor-cocaine and nor-cocaethylene were consistently the lowest of all cocaine metabolites. At benzoylecgonine concentrations below 100 ng/mL, ecgonine was present at the highest concentrations. In 20 urine specimens, benzoylecgonine and ecgonine median concentrations (range) were 54 (0-47) and 418 ng/mL (95-684), respectively. Therefore, detection of ecgonine is advantageous when benzoylecgonine concentrations are below 100 ng/mL.     

The synthesis and electronic structure of a novel [NiS4Fe2(CO)6] radical cluster: implications for the active site of the [NiFe] hydrogenases

A novel [NiS4Fe2(CO)6]cluster (1: 'S(4)'=(CH(3)C(6)H(3)S(2))(2)(CH(2))(3)) has been synthesised, structurally characterised and has been shown to undergo a chemically reversible reduction process at -1.31 V versus Fc(+)/Fc to generate the EPR-active monoanion 1(-). Multifrequency Q-, X- and S-band EPR spectra of (61)Ni-enriched 1(-) show a well-resolved quartet hyperfine splitting in the low-field region due to the interaction with a single (61)Ni (I=3/2) nucleus. Simulations of the EPR spectra require the introduction of a single angle of non-coincidence between g(1) and A(1), and g(3) and A(3) to reproduce all of the features in the S- and X-band spectra. This behaviour provides a rare example of the detection and measurement of non-coincidence effects from frozen-solution EPR spectra without the need for single-crystal measurements, and in which the S-band experiment is sensitive to the non-coincidence. An analysis of the EPR spectra of 1(-) reveals a 24 % Ni contribution to the SOMO in 1(-), supporting a delocalisation of the spin-density across the NiFe(2) cluster. This observation is supported by IR spectroscopic results which show that the CO stretching frequencies, nu(CO), shift to lower frequency by about 70 cm(-1) when 1 is reduced to 1(-). Density functional calculations provide a framework for the interpretation of the spectroscopic properties of 1(-) and suggest that the SOMO is delocalised over the whole cluster, but with little S-centre participation. This electronic structure contrasts with that of the Ni-A, -B, -C and -L forms of [NiFe] hydrogenase in which there is considerable S participation in the SOMO.     

An IR Study on Adsorption of CO and NO on Copper Ion-exchanged Zeolite Beta

Thee adsorption of CO and NO on copper ion-exchanged zeolite Beta was investigated using IR method.It was found that the thermalvacuum pretreatment procedure could result in the reduction of Cu2 ions in zeolite Beta.The adsorption of CO on Cu sites in zeolite Beta closely follows Langmuir isotherm.Another Cu species may form during the reaction between water and CO.The catalytic decomposition of NO on the zeolite was observed at room temperature,indicating that the decomposition reaction may occur between two coordinated NO ligands of the same dinitrosyhc complex.Furthermore,the appearance of two series of NO adsorption bands reveals that copper ions existing at different cation sites may have different effect on the adsorption and decomposition of NO molecules.     

Curing of a maleimide model compound

A monofunctional maleimide-ended model compound was synthesized and purified. The thermal curing of this compound was followed by size exclusion chromatography and the molecular masses of the oligomers formed during the curing reaction were determined by mass spectroscopy. It was found that high molecular mass species were not thermally stable. At high temperature and after enough time, a strong decrease in the polydispersity of the oligomers and a significantly preferential formation of trimer were observed. From ¹³C-NMR characterization, a five membered ring structure was found for the trimer, which explains the thermal stability of this species. © 1995 John Wiley & Sons, Inc.     

Functionalization of the macropolyhedral borate anion cluster [B22H22]: isolation and characterization of the OH and OEt derivatives

Preparation and characterization of the first derivatives of the fused macropolyhedral anion [B₂₂H₂₂]²⁻ are reported. The species [B₂₂H₂₁OH]²⁻ (1) and [B₂₂H₂₁OEt]²⁻ (2) are obtained from workup of the products of the reaction between HgBr₂ and [NBzlEt₃]₂[B₂₂H₂₂]; a cluster involving the conjoining of a closo-B₁₂ icosahedron with a nido-B₁₀ cluster. Washing the products with ethanol followed by thin-layer chromatography allows the isolation of 1 and 2, reproducibly, in yields of 27 and 20%, respectively. The species were characterized by NMR spectroscopy, elemental analysis and X-ray diffraction studies. The crystal structure determinations of the two species identify novel features. Apparently the influence of the O atoms in the ions [B₂₂H₂₁OH]²⁻ and [B₂₂H₂₁OEt]²⁻ results in the lengthening of what was a gunwale B---B connection adjacent to the junction of the two cages such that the distances are 2.180 and 2.230 Å, respectively. These latter are longer than the corresponding distance in the parent species [B₂₂H₂₂]²⁻, which is 2.09 Å; quite long for a normal B---B distance. Thus it is assumed that these B atoms, in 1 and 2, one of which bears the substituent, are not bonded to each other.     

Unusual iron(III) ate complexes stabilized by Li-pi interactions

Several iron(III) complexes incorporating diamidoether ligands are described. The reaction between [Li(2)[RN(SiMe(2))](2)O] and FeX(3) (X=Cl or Br; R=2,4,6-Me(3)Ph or 2,6-iPr(2)Ph) form unusual ate complexes, [FeX(2)Li[RN(SiMe(2))](2)O](2) (2, X=Cl, R=2,4,6-Me(3)Ph; 3, X=Br, R=2,4,6-Me(3)Ph; 4, X=Cl, R=2,6-iPr(2)Ph) which are stabilized by Li-pi interactions. These dimeric iron(III)-diamido complexes exhibit magnetic behaviour characteristic of uncoupled high spin (S= 5/2 ) iron(III) centres. They also undergo halide metathesis resulting in reduced iron(II) species. Thus, reaction of 2 with alkyllithium reagents leads to the formation of iron(II) dimer [Fe[Me(3)PhN(SiMe(2))](2)O](2) (6). Similarly, the previously reported iron(III)-diamido complex [FeCl[tBuN(SiMe(2))](2)O](2) (1) reacts with LiPPh(2) to yield the iron(II) dimer [Fe[tBuN(SiMe(2))](2)O](2) but reaction with LiNPh(2) gives the iron(II) product [Fe(2)(NPh(2))(2)[tBuN(SiMe(2))](2)O] (5). Some redox chemistry is also observed as side reactions in the syntheses of 2-4, yielding THF adducts of FeX(2): the one-dimensional chain [FeBr(2)(THF)(2)](n) (7) and the cluster [Fe(4)Cl(8)(THF)(6)]. The X-ray crystal structures of 3, 5 and 7 are described.     

Fourier Transform Infrared Spectroscopy and Solid Phase Extraction Applied to the Determination of Oil and Grease in Water Matrices

 The solid phase extraction as a solvent-free method for the analysis of oil and grease in waters was studied. The use of a PTFE surface as a solid phase allows the retention of the volatile fraction of oil and grease, and further analysis of carbon–hydrogen bonds using infrared spectroscopy can be done on the surface. Various oils and grease samples were tested: n-hexadecane, n-tetradecane, n-nonadecane, n-docosane, isooctane, diesel oil and gasoline. Temperatures from 25° to 90 °C and a range of heating times were checked for extraction. Precision tests showed relative standard deviation values of around 10% in several samples of the same concentration. Calibration lines of n-hexadecane showed high correlation coefficients from 0.9 to 30 mg/l. Recoveries for the various oils using different calibration lines showed values from 90 to 110%. The method described here is fast and clean, and allows reproducible measurements of oil and grease in water that do not require the use of a solvent. Received March 1, 2001; accepted August 15, 2001; published online July 15, 2002     

Redox-induced η5 ⇔ η3 haptotropy of the fluorenyl ligand in 9-substituted η5-fluorenylmanganesetricarbonyl complexes

It has been shown by cyclic voltammetry in THF within the –90 to 40 °C temperature range that fluorenyl (⁵-9-R-C₁₃H₈)Mn(CO)₃ complexes (R=Bu^t (3) and Ph (4)) undergo two-electron reduction to form allyl type [(³-9-R-C₁₃H₈)Mn(CO)₃]^2– dianions as final products. At low temperatures complexes3 and4 are reduced in two one-electron steps according to the EEC-scheme. The first step is reversible and corresponds to the formation of 19-radical anions 3^–. and 4^–.. TheE ⁰ values for redox pairs3 ^0/–. and4 ^0/–. are –1.88 and –1.73 V, respectively. The further reduction of radical anions3 ^–. and4 ^–. at more negative potentials is accompanied by fast ^{5 3} haptocoordination of the fluorenyl ligand to form 18-dianions [(³-9-R-C₁₃H₈)Mn(CO)₃]^2–. These dianions obtained by the reduction of complexes3 and4 by the radical anion of pyrene are stable at –80 °C and are characterized by their IR spectra. At room temperature the ^{5 3} hapticity change is a fast and reversible process occurring at the step of 19-radical anions3 ^–. and4 ^–. and leading to the electron deficient 17-species [(³-9-R-C₁₃H₈)Mn(CO)₃]^–., which are reduced easier than the initial complexes. As a result, complexes3 and4 are reduced to the corresponding dianions [(³-9-R-C₁₃H₈)Mn(CO)₃]^2– at room temperature in one reversible two-electron step according to the ECE-scheme. Reactivities of 19e^–-species of the isomeric ⁵- and ⁶-fluorenylmanganesetricarbonyl complexes are compared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1347–1353, July, 1995.The work was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-05209) and the International Science Foundation (Grant No. REV 000).