Structure, Stability and Vibrational Spectra of LaC_5~n(n=-1,0,+1) Clusters

用密度泛含方法研究了ＬａＣ５ｎ（ｎ＝－１，０，＋１）分子簇的结构和稳定性及振动光谱，对这个六原子体系提出了三种可能构型，点群结构为Ｃ２ｖ对称性．第一个构型为Ｌａ接在弯曲的Ｃ５链上，第二个是Ｌａ通过二个键与Ｃ５环相连第三个是Ｌａ通过一个键与Ｃ５环相连；结果表明，第一个构型即当Ｌａ接在弯曲的Ｃ５链上时能量最低．振动光谱分析指出，当ｎ＝－１时，第二个构型为局域极小值；当ｎ＝＋１时，第一个和第二个构型为局域极小值；对ｎ＝０，局域极小值没有找到.

Theoretical Investigation of LaC~n and La_2C~n(n=-1,0,+1)Clusters

用密度泛函方法研究了ＬａＣｎ及Ｌａ２Ｃｎ（ｎ＝－１，０，＋１）分子簇的结构和稳定性．对Ｌａ２Ｃｎ体系，提出了两种可能构型，其中一种具有Ｃ２ｖ对称性，另一种具有Ｄ∞ｈ对称性．计算结果表明，对Ｌａ２Ｃｎ，当ｎ＝＋１，－１时，线状结构最稳定，并且在ｎ＝＋１时，Ｃ２ｖ结构极不稳定有收敛向线状结构的趋势．而当ｎ＝０时，Ｃ２ｖ结构最稳定．最后还计算了ＬａＣ和Ｌａ２Ｃ分子簇的电子亲和势和离化能.

Theoretical investigation of LaCn+ (n=2-8) clusters

LaCn+ (n = 2-8) have been studied using Hartree-Fock (HF) and B3LYP density functional method. The results indicated that at both levels, isomers with C-2v, C-s symmetry for n = 2, and edge insertion isomer for n = 4, 6, 8, as well as edge binding isomer for n = 3, 5, 7 were found as ground states. This is in good agreement with experimental results. The exceptional case is for n = 6 at B3LYP level, in which edge insertion and edge binding isomers were computed to be near isoenergetic. (C) 1997 Elsevier Science B.V.

Theoretical investigation of small lathanum carbide clusters

LaC2+, LaC22+, LaC3 and LaC3- clusters have been studied using B3LYP density functional method. Four isomers with C-2v, C-s, C-infinity v and D-infinity h symmetry were presented for LaC2+ and LaC22+. Meanwhile, two spin states, namely, singlet and triplet for LaC2+, doublet and quartet for LaC22+ were considered The results indicated that ring isomers with C-2v and C-s symmetry are the most stable for La-C2(+) at both spin states and for LaC22+ at quartet state. Whereas for LaC22+ at doublet state, linear isomer with C-infinity v symmetry is energetically favored, For LaC3 and LaC3- clusters,, three isomers have been presented for each cluster, that is, two ring isomers with C-2v symmetry ( in one of them, La forms two single bonds with two carbons, and in another, La forms a double bond with carbon), and one linear isomer with C-infinity v symmetry. The results revealed that the ring isomer in which La forms two single bonds with carbons is the lowest in energy.

Rapid automated in-situ monitoring of total dissolved iron and total dissolved manganese in underground water by reverse-flow injection with chemiluminescence detection during the process of water treatment

Measurement of iron and manganese is very important in evaluating the quality of natural waters. We have constructed an automated Fe(II), total dissolved iron(TDI), Mn(II), and total dissolved manganese(TDM) analysis system for the quality control of underground drinking water by reverse flow injection analysis and chemiluminescence detection(rFIA-CL), The method is based on the measurement of the metal-catalyzed light emission from luminol oxidation by potassium periodate. The typical signal is a narrow peak, in which the height is proportional to light emitted and hence to the concentration of metal ions. The detection limits were 3 x 10(-6) mu g ml(-1) for Fe(II) and the linear range extents up to 1.0 x 10(-4) and 5 x 10(-6) mu g ml(-1) for Mn(II) cover a linear range to 1.0 x 10(-4) mu g ml(-1). This method was used for automated in-situ monitoring of total dissolved iron and total dissolved in underground water during water treatment. (C) 1997 Elsevier Science B.V.

Iron(II)-8-quinolinol/MCM-41-catalyzed phenol hydroxylation and reaction mechanism

Iron(II)-8-quinolino/MCM-41 is prepared. Its catalysis is studied in phenol hydroxylation using H2O2 (30%) as oxidant. The experiment shows that Iron(II)-8-quinolinol/MCM-41 has good catalytic activity and desired stability. Based on cyclic voltammetry, ESR, and UV-visible spectra studies of iron(II)-8-quinolinol complex in liquid phase, a radical substitution mechanism is proposed and used to demonstrate the experimental facts clearly. (C) 1997 Academic Press.

Ab initio study of C-9 and LaC9+ clusters

The energies and geometries of C-9 and LaC9+ clusters were calculated at HF, MP2 and DFT levels. For C-9, all theoretical levels show that the linear chain is the most stable structure. For LaC9+, two isomers were considered. In the first case La has two single bonds (A), while it forms a double bond in the second (B). Our results showed that in HF calculation, B is marginally more stable than A, while for MP2 and DFT, A is favored. Our results also revealed that there is not enough space for C-9 ring to accommodate lanthanum. Our conclusion agrees well with experiment.

Studies on preparation of iron phenanthroline and 8-hydroxyquinoline complexes/Y zeolite, characterization and catalytic hydroxylation of phenol

Iron phenanthroline - and 8 - hydroxyquinoline complexes /Y zeolite, denoted a FePhen/Y and FeOx/Y respectively, were prepared; The formation of the metal complexes mentioned above within the cages of Y zeolite and their crystal structures were determined by elemental analyses, diffuse reflectance UV-Vis,SEM,BET,and XRD methods; The influence of experimental parameters upon phenol conversion and product selectivities were investigated as well.

Phenol hydroxylation by iron(II) phenanthroline: The reaction mechanism

Phenol hydroxylation catalyzed by iron(II)-1,10-phenanthroline is investigated through kinetics, ESR, W-Vis as well as cyclic voltammogram studies. The optimum reaction conditions are obtained for diphenols production. Radical substitution mechanism is first proposed to explain the effects of pH, reaction medium and other factors on the phenol hydroxylation with H2O2 as oxidant, and found that the coexisting of iron(II)-1,10-phenanthroline and iron(III)-1,10-phenanthroline is the key for phenol hydroxylation to occur with H2O2 as oxygen donor.

Hydroxylation of phenol by iron(II)-phenanthroline(Phen)/MCM-41 zeolite

MCM-41 zeolite and Tron (II)-Phen/MCM-41 zeolite have been prepared and characterized by XRD, IR, NH3-TPD, HET and UV-Vis. The Iron( II)-Phen/MCM-41 zeolite+30% H2O2 system is capable for catalyzing hydroxylation of phenol.

Synthesis and characterization of a new double-cubane Mo-Fe-S cluster compound, [NEt(4)](3)[Mo2Fe6S8(mu-OMe)(3)(SPh)(3)Cl-3]

The new double-cubane cluster compound [NEt(4)](3)[Mo2Fe6S8(mu-OMe)(3)(SPh)(3)Cl-3] is synthesized from (NH4)(2)MoS4, FeCl3, Fe powder, S powder, NaSPh and NEt(4)Br in MeOH-DMF, its crystal structure is determined by X-ray crystallography, and results of XPS indicate a valence state of +4 for Mo.

Hydroxylation of phenol by iron(II)-phenanthroline(Phen) MCM-41 zeolite

MCM-41 mesoporous molecular sieve and iron(II)-Phen/MCM-41 have been prepared and characterized by XRD, IR, NH3-TPD, BET and UV-Vis. The iron(II)-Phen/MCM-41 molecular sieve + 30% H2O2 system is capable of performing hydroxylation of phenol.

ELECTROACTIVE COATINGS OF DICYANO-BIS(1,10-PHENANTHROLINE)IRON(II) ATTACHED TO NAFION POLYMER FILM-MODIFIED ELECTRODES VIA ADSORPTION

A dicyano-bis(1,10-phenanthroline)iron(II) modified elecrode was prepared. The voltammetric and the spectroelectrochemical behavior of this electrode were investigated. The influence of pH and the amount of Nafion and dicyano-bis(1,10-phenanthroline) iron(II) (DBPI) used in the electrode preparation on the electrochemical behavior is presented.

MECHANISM OF IRON INHIBITION BY STEARIC-ACID LANGMUIR-BLODGETT MONOLAYERS

Using the Langmuir-Blodgett (LB) technique, stearic acid (SA) monolayers were deposited onto the surface of an iron (Fe) electrode to study the inhibition effect and the mechanism of SA in a neutral medium. Molecular orientation and the number of deposited monolayers of SA were shown to have marked effects on inhibition of Fe corrosion. The inhibition mechanism depended mainly on blocking.