- Complexation of High-Valency Mid-Actinides by a Lipophilic Schiff Base Ligand: Synthesis, Structural Characterization, and Progress toward Selective Extraction
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Separation of U, Np, and Pu from used nuclear fuel (UNF) would result in lower long-Term radiotoxicity, alleviating constraints on the storage and handling of the material. The complexity of UNF requires several industrial-Scale processes with multiple waste streams. A one-Step solution to the group removal of the elements, U-Pu, is desirable. Here we present a possible solution to group actinide separation utilizing the unique dioxy conformation of An(V/VI) cations and demonstrate the ability of a tetradentate lipophilic Schiff base ligand (L) to yield isostructural complexes of the general formula [(AnVIO2)(L)(CH3CN)] (where An = U, Np, or Pu). Extraction of An(VI) with the ligand follows the order U > Pu > Np, likely reflecting the decreased stability of the hexavalent actinide across the series. While the results indicate a promising path toward a one-Step process, further improvement in the ligand stability and control of the redox chemistry is required.
- Bustillos, Christian G.,Hawkins, Cory A.,Copping, Roy,Reilly, Sean D.,Scott, Brian L.,May, Iain,Nilsson, Mikael
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- Hydroxy- and alkoxy-bridged dinuclear uranyl-Schiff base complexes: Hydrolysis, transamination and extraction studies
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The reaction of uranyl nitrate with 1,3-bis(salicylideneamino)-2-propanol (H3L1) and 1,3-bis(3,5-di-tert-butylsalicylideneamino)-2-propanol (H3L2) in the presence of triethylamine (Et3N) yielded hydroxy- and alkoxy-bridged dinuclear complexes; [(UO2) 2(L1)(OH)(MeOH)2]?(MeOH)2 (1?(MeOH)2) and [(UO2)2(L2)(OH)(MeOH) 2]?(MeOH)2 (2?(MeOH)2). The crystal structures of 1?(DMF)2 and 2?(DMF)2 exhibit an unsymmetrical central U2O2 core involving bridging alkoxy- and hydroxy-oxygen atoms. The geometry around the uranium center in 1?(DMF)2 and 2?(DMF)2 is that of a distorted pentagonal bipyramid with the solvent molecule occupying the fifth coordination site. The flexible nature of the ligand backbone is more pronounced in 2?(DMF)2 compared to 1?(DMF)2, yielding two molecules per unit cell in different conformations. Under similar reaction conditions, using ethylenediamine as a base, the respective Salen-based uranyl compounds, [UO2(Salen)(MeOH)] (3) and [UO2(Bu t2-Salen)(MeOH)] (4) are obtained due to transamination of the ligand backbone. Complexes 1?(MeOH)2 and 2?(MeOH) 2 when reacted with an excess of ethylenediamine failed to yield the respective Salen-based complexes, 3 and 4, respectively. The new compounds have been characterized using solution (NMR and UV-Vis) and solid-state (IR, X-ray crystallography) techniques. Hydrolysis of 1?(MeOH)2 and 2?(MeOH)2 in the pH range 1-14 was studied using UV-Vis spectroscopy and compared with the hydrolysis of 3 and [UO2(Salophen) (MeOH)] (5). A two-phase extraction study suggests quantitative removal of uranyl ions from the aqueous phase at higher pH conditions. The Royal Society of Chemistry 2008.
- Bharara, Mohan S.,Heflin, Kathryn,Tonks, Stephen,Strawbridge, Kara L.,Gorden, Anne E. V.
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- Salen-based coordination polymers of manganese and the rare-earth elements: Synthesis and catalytic aerobic epoxidation of olefins
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Treatment of N,N'-bis(4carboxysalicylidene)ethylenediamine (H 4L), with MnCl2·(H2O)4, and Ln(NO3)3·(H2O)m (Ln=Nd, Eu, Gd, Dy, Tb), in the presence of N,N-dimethylforma
- Bhunia, Asamanjoy,Gotthardt, Meike A.,Yadav, Munendra,Gamer, Michael T.,Eichhoefer, Andreas,Kleist, Wolfgang,Roesky, Peter W.
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- Direct observation of enantiomer discrimination of epoxides by chiral salen complexes using ENDOR
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Electron nuclear double resonance (ENDOR) spectroscopy was used to investigate the weak enantioselective binding between chiral salen complexes [VO(1)] ((R,R)- and (S,S)-vanadyl N,N-bis(3,5-di-tert-butylsalcylidene)-1,2-cyclohexanediamine) and chiral epoxides (e.g., (R)-/(S)-propylene epoxide, 5) in frozen (10 K) solution. Differences in epoxide binding by enatiomers of [VO(1)] was evidenced by changes to the 1H epoxide derived peaks in the ENDOR spectra, such that (R,R)-[VO(1)] + (R)-5 and (R,R)-[VO(1)] + (S)-5 yield noticeably different spectra. These changes were assigned to the small structural differences between the diastereomeric metal-epoxide adducts. Simulation of the spectra revealed differences in the VO...1Hepoxide distances for the diastereomeric pairs, which was confirmed by a complementary set of density functional theory (DFT) calculations. While the epoxide molecule is very weakly coordinated, ENDOR measurements of the racemic complex in racemic epoxide nevertheless indicated the preferential coordination of the (R)-5 to (R,R)-[VO(1)] (likewise (S)-(5) to (S,S)-[VO(1)]), which is favored over the binding of (S)-5 epoxide to (R,R)-[VO(1)] (and likewise (R)-5 epoxide to (S,S)-[VO(1)]). This demonstrates the unique power of the ENDOR technique to resolve weak chiral interactions for which EPR spectroscopy alone lacks sufficient resolution. Copyright
- Fallis, Ian A.,Murphy, Damien M.,Willock, David J.,Tucker, Richard J.,Farley, Robert D.,Jenkins, Robert,Strevens, Robert R.
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- Salen manganese (III) complexes as catalysts for R-(+)-limonene oxidation
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The epoxidation of R-(+)-limonene using in situ generated dimethyldioxirane (DMD) as the oxidizing agent and four Jacobsen-type catalysts ((R,R)-Jacobsen, (S,S)-Jacobsen, racemic Jacobsen and achiral Jacobsen) was examined. The effect of the amount of KHSO5 and acetone in the catalyzed and un-catalyzed reaction was also assessed. The main reaction products were diepoxide and endocyclic monoepoxide. In the absence of catalyst, the amount of KHSO5 did not significantly influence conversion and selectivity. The catalyst can be segregated to a different phase and separated from the reaction media when the amount of KHSO5 is above the stoichiometric ratio, R-(+)-limonene/KHSO5 = 0.5 mmol/mmol, and acetone/mmol R-(+)-limonene = 2 mL/mmol. However, when the amount of KHSO5 is below the stoichiometric ratio (R-(+)-limonene/KHSO5 = 1.5 mmol/mmol) the catalyst is difficult to separate. Under the reaction conditions of this study, when the catalyst is segregated, no effect of the catalyst chiral center, (R,R)-Jacobsen or (S,S)-Jacobsen, was found on conversion and selectivity. Additionally, the (R,R)-Jacobsen's catalyst proved to be very stable to oxidative degradation.
- Cubillos, Jairo,Vásquez, Santiago,Montes de Correa, Consuelo
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- Synthesis and Characterization of Structurally Diverse Alkaline-Earth Salen Compounds for Subterranean Fluid Flow Tracking
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A family of magnesium and calcium salen-derivatives was synthesized and characterized for use as subterranean fluid flow monitors. For the Mg complexes, di-n-butyl magnesium ([Mg(Bun)2]) was reacted with N,N′-ethylene bis(salicyliden
- Boyle, Timothy J.,Sears, Jeremiah M.,Greathouse, Jeffery A.,Perales, Diana,Cramer, Roger,Staples, Orion,Rheingold, Arnold L.,Coker, Eric N.,Roper, Todd M.,Kemp, Richard A.
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- Oxidative Desulfurization of Dibenzothiophene Using Cobalt (II) Complexes with Substituted Salen-Type Ligands as Catalysts in Model Fuel Oil
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Three cobalt(II)-salen complexes (CoL1, CoL2 and CoL3) were synthesized via the reaction of the three tetradentate ligands as N,N′-ethylenebis(salicylimine) L1, N,N′-ethylenebis(3-tert-butylsalicylimine) L2 and N,N′-ethylenebis(3,5-di-tert-butylsalicylimine) L3, with a stoichiometric amount of cobalt(II) acetate tetrahydrate, respectively. All the three complexes were studied as oxidative desulfurization catalyst on dibenzothiophene taken in model fuel oil n-dodecane. The acetonitrile used as an extracting solvent and H2O2 as an oxidant. Comparatively CoL3 proved to be the best catalyst which showed the 76% DBT removal at the optimized conditions. The nth-order kinetic model is the best way to represent oxidation kinetics of complexes. Graphic Abstract: [Figure not available: see fulltext.]This cobalt(II) Schiffs base complexes were studied as catalyst for oxidative desulfurization of dibenzothiphene (DBT) taken as model sulphur compounds in fuel model oil (n-dodecane) using H2O2 as oxidant and acetonitrile as extracting solvent for DBT sulfone in a batch experiment.
- Tripathi, Deependra,Singh, Raj K.
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p. 713 - 719
(2020/08/06)
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- Alteration of electronic effect causes change in rate determining step: Oxovanadium(IV)–salen catalyzed sulfoxidation of phenylmercaptoacetic acids by hydrogen peroxide
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Sulfoxidation of a series of phenylmercaptoacetic acids (PMAA) by hydrogen peroxide catalysed by oxovanadium(IV)–salen complexes has been carried out spectrophotometrically in 100% acetonitrile medium. The formation and involvement of hydroperoxovanadium(
- Kavitha,Subramaniam
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- Site-Selective Copper-Catalyzed Azidation of Benzylic C-H Bonds
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Site selectivity represents a key challenge for non-directed C-H functionalization, even when the C-H bond is intrinsically reactive. Here, we report a copper-catalyzed method for benzylic C-H azidation of diverse molecules. Experimental and density functional theory studies suggest the benzyl radical reacts with a CuII-azide species via a radical-polar crossover pathway. Comparison of this method with other C-H azidation methods highlights its unique site selectivity, and conversions of the benzyl azide products into amine, triazole, tetrazole, and pyrrole functional groups highlight the broad utility of this method for target molecule synthesis and medicinal chemistry.
- Suh, Sung-Eun,Chen, Si-Jie,Mandal, Mukunda,Guzei, Ilia A.,Cramer, Christopher J.,Stahl, Shannon S.
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supporting information
p. 11388 - 11393
(2020/07/21)
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- Investigation of the dinuclear effect of aluminum complexes in the ring-opening polymerization of ε-caprolactone
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A series of aluminum (Al) complexes bearing hydrazine-bridging Schiff base and salen ligands were synthesized and investigated as catalysts for the ring-opening polymerization of ε-caprolactone (CL). The introduction of steric bulky groups increases the catalytic activity of the corresponding mononuclear aluminum complex. However, the opposite phenomenon was observed in dinuclear Al complexes bearing salen ligands because the steric repulsion reduced the cooperative activation mechanism in the dinuclear Al system. Among these Al complexes, LN2Bu-Al2Me4 bearing a hydrazine-bridging Schiff base ligand had the highest catalytic activity, approximately 3- to 11-fold higher than that of dinuclear Al complexes bearing salen ligands and mononuclear Al complexes bearing Schiff base ligands. Density functional theory calculations revealed that the mechanism of the coordination of CL to one Al center was initiated by the benzyl alkoxide of another Al center.
- Hsu, Chiao-Yin,Tseng, Hsi-Ching,Vandavasi, Jaya Kishore,Lu, Wei-Yi,Wang, Li-Fang,Chiang, Michael Y.,Lai, Yi-Chun,Chen, Hsing-Yin,Chen, Hsuan-Ying
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p. 18851 - 18860
(2017/04/10)
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- Schiff base iron compound, preparation method thereof and application of Schiff base iron compound as catalyst
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The invention provides a Schiff base iron compound, a preparation method thereof and application of the Schiff base iron compound as a catalyst. The Schiff base iron compound has a structure represented by a formula (I) (shown in the description), wherein
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Paragraph 0088; 0089
(2017/09/02)
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- Encapsulation of SALEN- and SALHD-Mn(III) complexes in an Al-pillared clay for bicarbonate-assisted catalytic epoxidation of cyclohexene
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[Mn(3,5-dtSALEN)Cl] (I) and [Mn(3,5-dtSALHD)Cl] (II) complexes (3,5-dtSALEN = N,N′-bis(3,5-di-tert-butylsalicylaldehyde)ethylenediamine; 3,5-dtSALHD = N′N-bis-(3,5-di-tert-butylsalicylaldehyde)-1,2-cyclohexanediamine) were successfully encapsulated within
- Garcia, Ana M.,Moreno, Viviana,Delgado, Sonia X.,Ramírez, Alfonso E.,Vargas, Luis A.,Vicente, Miguel á.,Gil, Antonio,Galeano, Luis A.
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- Oxovanadium(IV)-salen ion catalyzed H2O2 oxidation of tertiary amines to n-oxides- critical role of acetate ion as external axial ligand
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The oxovanadium(IV)-salen ion catalyzed H2O2 oxidation of N,N-dimethylaniline forms N-oxide as the product of the reaction. The reaction follows Michaelis-Menten kinetics and the rate of the reaction is accelerated by electron donating groups present in the substrate as well as in the salen ligand. This peculiar substituent effect is accounted for in terms of rate determining bond formation between peroxo bond of the oxidant and the N-atom of the substrate in the transition state. Trichloroacetic acid (TCA) shifts the λmax value of the oxidant to the red region and catalyzes reaction enormously. The cleavage of N£O bond by vanadium complex leads to moderate yield of the product. But the percentage yield of the product becomes excellent in the presence of TCA.
- Mathavan, Alagarsamy,Ramdass, Arumugam,Ramachandran, Mohanraj,Rajagopal, Seenivasan
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p. 315 - 326
(2015/04/14)
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- Selective oxidative homo-and cross-coupling of phenols with aerobic catalysts
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Simple catalysts that use atom-economical oxygen as the terminal oxidant to accomplish selective ortho-ortho, ortho-para, or para-para homo-couplings of phenols are described. In addition, chromium salen catalysts have been discovered as uniquely effective in the cross-coupling of different phenols with high chemo-and regioselectivity.
- Lee, Young Eun,Cao, Trung,Torruellas, Carilyn,Kozlowski, Marisa C.
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supporting information
p. 6782 - 6785
(2014/06/09)
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- Electrochemical properties of VO salen complexes
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Electrochemical properties of a series of differently substituted vanadyl salen complexes were investigated using cyclic voltammetry in different solvents. Results obtained show that the salen structure stabilizes the oxidized forms and that the effects of substituents on the oxidation potential correlate with the electronic density of the metal. Also the role of the donicity of the solvent in influencing the redox potentials of the studied complexes has been evidenced. Moreover, the variations of the observed potentials can be qualitatively correlated to the catalytic activity of vanadyl salen derivatives in the oxidation of thioethers.
- Galloni, Pierluca,Coletti, Alessia,Floris, Barbara,Conte, Valeria
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p. 144 - 148
(2014/07/08)
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- Vanadium-catalyzed solvent-free synthesis of quaternary α-trifluoromethyl nitriles by electrophilic trifluoromethylation
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The direct electrophilic trifluoromethylation of silyl ketene imines (SKIs) with hypervalent iodine reagents leads to the formation of quaternary α-trifluoromethyl nitriles in good yields. This new reaction has been carried out with a variety of substitut
- Früh, Natalja,Togni, Antonio
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supporting information
p. 10813 - 10816
(2015/05/13)
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- Facile, efficient, and diastereoselective synthesis of heterohelicene-like molecules
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A concise and efficient route to new and interesting heterohelicene-like molecules has been developed through the one-pot, cascade reductive coupling reaction of o-hydroxydiimines or o-nitrodiimines and triphosgene in the presence of TiCl4/Sm.
- Lin, Wei,Dou, Guo-Lan,Hu, Ming-Hua,Cao, Cheng-Pao,Huang, Zhi-Bin,Shi, Da-Qing
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supporting information
p. 1238 - 1241
(2013/04/23)
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- Salophen and salen oxo vanadium complexes as catalysts of sulfides oxidation with H2O2: Mechanistic insights
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The application of V(V) catalysts in oxidation of sulfides with peroxides offers an efficient procedure, that is compatible with different functional groups, and leads to good yields and selectivities. However, the understanding of the factors affecting the reactivity of different catalysts is still far to be complete. An experimental and theoretical study on a series of V(V) complexes containing variously substituted salen and salophen ligands is reported with the aim to correlate the activity of the catalysts with the electronic character of the vanadium center. The results obtained indicate that steric factors play a major role in determining the outcome of the reaction, often overcoming the electronic effects. Theoretical results suggest the intervention in the catalytic cycle of an hydroperoxo vanadium species.
- Coletti,Galloni,Sartorel,Conte,Floris
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- Structural, spectral, electrochemical and catalytic reactivity studies of a series of N2O2 chelated palladium(II) complexes
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A series of neutral salicylaldiminato Pd(II) complexes have been synthesized and characterized. Spectral and electrochemical properties of the complexes in the solution phase have been investigated. The structure of complex 9 has been confirmed by X-ray a
- Ulusoy, Mahmut,Birel, Oezguel,Ahin, Onur,Bueyuekguengoer, Orhan,Cetinkaya, Bekir
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scheme or table
p. 141 - 148
(2012/07/03)
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- Synthesis and properties of salen-aluminum complexes as a novel class of color-tunable luminophores
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A series of salen-aluminum complexes, [{(R5)2- salen(3-tBu)2}Al(OC6H4-ZJ-C6H 5)] (salen = N,N'-bis(salicylidene)ethylenediamine; R5 = H (1), tBu (2), Br (3), Ph (4), O
- Hwang, Kyu Young,Kim, Hyoseok,Lee, Yoon Sup,Lee, Min Hyung,Do, Youngkyu
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experimental part
p. 6478 - 6487
(2010/02/28)
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- Stereoselective ring-opening polymerization of a racemic lactide by using achiral salen- and homosalen-aluminum complexes
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Highly isotactic polylactide or poly(lactic acid) is synthesized in a ring-opening polymerization (ROP) of racemic lactide with achiral salen- and homosalen-aluminum complexes (salenH2 = N,N′-bis(salicylidene) ethylene-1,2-diamine; homosalenH2 = N,N′-bis(salicylidene) trimethylene-1,3-diamine). A systematic exploration of ligands demonstrates the importance of the steric influence of the Schiff base moiety on the degree of isotacticity and the backbone for high activity. The complexes prepared in situ are pure enough to apply to the polymerizations without purification. The crystal structures of the key complexes are elucidated by X-ray diffraction, which confirms that they are chiral. However. analysis of the 1H and 13C NMR spec tra unambiguously demonstrates that their conformations are so flexible that the chiral environment of the complexes cannot be maintained in solution at 25°C and that the complexes are achiral under the polymerization conditions. The flexibility of the back-bone in the propagation steps is also documented. Hence, the isotacticity of the polymer occurs due to a chain-end control mechanism. The highest reactivity in the present system is obtained with the homosalen ligand with 2.2-dimethyl substituents in the backbone (ArCH=NCH2CMe2CH2N=CHAr), whereas tBuMe2Si substituents at the 3-positions of the salicylidene moieties lead to the highest selectivity (Pmeso,= 0.98; T m = 210°C). The ratio of the rate constants in the ROPs of racemic lactide and L-lactide is found to correlate with the stereoselectivity in the present system. The complex can be utilized in bulk polymerization, which is the most attractive in industry, although with some loss of stereoselectivity at high temperature, and the afforded polymer shows a higher melting temperature (Pmeso = 0.92, Tm up to 189°C) than that of homochiral poly(L-lactide) (Tm = 162-180°C). The "livingness" of the bulk polymerization at 130°C is maintained even at a high conversion (97-98%) and for an extended polymerization time (1-2 h).
- Nomura, Nobuyoshi,Ishii, Ryohei,Yamamoto, Yoshihiko,Kondo, Tadao
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p. 4433 - 4451
(2008/02/09)
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- Titanium-salen complexes as initiators for the ring opening polymerisation of rac-lactide
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A family of bis(iso-propoxide) titanium(iv) complexes supported by tetradentate Schiff base (salen) ligands has been synthesised and characterised, including a structural determination of N,N′-bis(6′-methylenimino- 2′,4′-di-tert-butylphenoxy)cyclohexyl-(1
- Gregson, Charlotte K.A.,Blackmore, Ian J.,Gibson, Vernon C.,Long, Nicholas J.,Marshall, Edward L.,White, Andrew J.P.
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p. 3134 - 3140
(2007/10/03)
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- Synthesis, spectroscopy, and electrochemistry of copper(II) complexes with N,N′-bis(3,5-di-t-butylsalicylideneimine) polymethylenediamine ligands
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Bulky salen CuLx derived from aliphatic polymethylene diamines, H2N-(CH2)x-NH2, where n = 2-6, and 3,5-di-t-butylsalicylaldehyde (H2Lx) and some corresponding tetrahydrosalan complexes (CuL′x) have been synthesized and characterized by their IR, UV - vis absorption and EPR spectra, by magnetic moments and by cyclic voltammetry in acetonitrile (for H 2Lx) and DMF (for CuLx). Complexes CuL x and CuL′x are magnetically normal (μexp = 1.83-1.91 μB). EPR spectra CuLx characterized by the axial g and ACu, tensors with g∥ > g⊥ and without 14N-shf resolution in CHCl3/toluene at 300 and 150K. The CV studies on acetonitrile solutions of H2L x revealed a well-defined quasi-reversible redox wave at E 1/2 = 0.95-1.15 V versus Ag/AgCl but CV of the CuLx complexes in DMF exhibit weak pronounced irreversible oxidation waves at E pa1, = 0.51 - 0.98 V and Epa1 = 1.16 - 1.33 V attributable to metal centered Cu(II/III) and ligand centered CuL x/CuLx+ couples, respectively. A poorly defined wave was observed for the quasi-reversible reduction Cu(II)/Cu(I) at potentials less than - 1.0 V.
- Kasumov, Veil T.,Koeksal, Fevzi
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p. 225 - 231
(2007/10/03)
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- Synthesis, spectroscopy and electrochemical behaviors of nickel(II) complexes with tetradentate shiff bases derived from 3,5-Bu2 t-salicylaldehyde
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Nickel(II) complexes of a series of N,N′-polymethylenebis(3,5-Bu2t- salicylaldimine) ligands containing 2,4-di-Bu2t-phenol arms, NiLx, were synthesized and their spectroscopic and redox properties were examined. The UV-vis, 1H NMR sp
- Kasumov, Veli T.,Oezalp-Yaman, Seniz,Tas, Esref
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p. 716 - 720
(2007/10/03)
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