- Zinc-containing block copolymer as a precursor for the in situ formation of nano ZnO and PMMA/ZnO nanocomposites
-
We report on the synthesis of highly transparent and UV-absorbing PMMA/ZnO nanocomposites prepared by hydrolysis of a ZnO precursor, the A-b-(AB) diblock copolymer, poly(methyl methacrylate)-block-poly(methyl methacrylate-co-(zinc methacrylate acetate)), PMMA-b-P(MMA-co-ZnMAAc), synthesized by RAFT polymerization. The zinc content of the block copolymers was in the range from 3 to 13 wt %. The PMMA block provides inherent compatibility with the PMMA matrix, whereas the second block, P(MMA-co-ZnMAAc) with zinc ions, acts as a polymeric precursor for the formation of ZnO nanoparticles. The amphiphilic block copolymer self-organizes in THF and THF/H2O in ordered nanostructures, thereby influencing the nanoparticle formation during the hydrolysis of the precursor block copolymer with KOH in a solvent mixture THF/H2O. The ZnO nanoparticles were rod-shaped with lengths up to 80 nm and a diameter of 14 nm and were redispersible in THF. Dispersions in THF and thin films of PMMA/ZnO nanocomposite exhibit excellent transparency in the visible range and good absorption in the UV range below 400 nm. The block copolymer was characterized by SEC, NMR, DLS, and TGA, while PMMA/ZnO nanocomposites were characterized by IR, XRD, UV-vis, and STEM.
- Kos, Tomaz,Anzlovar, Alojz,Pahovnik, David,Zagar, Ema,Orel, Zorica Crnjak,Zigon, Majda
-
-
Read Online
- Hierarchical ZnO aggregates assembled by orderly aligned nanorods for dye-sensitized solar cells
-
Hierarchical ZnO aggregates assembled by orderly aligned nanorods were prepared via a facile solvothermal method using diethylene glycol as solvent and zinc acetate dehydrate as precursor. Time dependent trails evidenced that the formation of the hierarchical aggregates experienced a multistep self-assembly process. Moreover, it was found that the reaction medium plays an important role in the assembling process and the diameter of the product could be tuned by simply altering the precursor dosage. The hierarchical product was further applied as scattering layer in bi-layered dye-sensitized solar cell (DSSC), and a high conversion efficiency of 5.2% was demonstrated, indicating a substantial improvement compared with the nanoparticle cell of 2.7%. Based on the optical and electrochemical investigations, the high conversion efficiency was mainly ascribed to the unique hierarchical structure of the ZnO aggregates. The rough surface of the nanorod subunits could enhance the dye loading capacity and the aggregates with micrometer sized diameter could improve the scattering effect. Moreover, the orderly aligned nanorods could minimize the grain boundaries, suppress the surface recombination and provide a direct pathway for fast electron transport, which therefore enhance the collection efficiency of the photoelectrons.
- Wu, Dapeng,Gao, Zhiyong,Xu, Fang,Chang, Jiuli,Tao, Wenguang,He, Jinjin,Gao, Shuyan,Jiang, Kai
-
-
Read Online
- Kinetics and mechanism of the isothermal dehydration of zinc acetate dihydrate
-
The overall kinetics of the thermal dehydration of zinc acetate dihydrate was investigated by means of isothermal mass-change measurements, complemented by microscopic observations of the reaction geometry and morphological change during the reaction. Under isothermal conditions, the compound loses its water of crystallization in a well-defined single step; Zn(CH3COO)2 · 2H2O → Zn(CH3COO)2 + 2H2O. The microscopic observations for the single crystals confirm that the reaction initiates at the edge surfaces of the hexagonal thin plate by nucleation and growth processes, consequently forming the reaction interface which advances inward, toward the center of the hexagon. The kinetic results obtained from the thermoanalytical measurements indicated agreement to the first-order law, in spite of the two-dimensional shrinkage of the reaction interface. This discrepancy is discussed in connection with the interactions of the elementary nucleation and growth processes at the reaction interfaces with the self-generated water vapor. The overall kinetic behavior of the crushed crystals of different particle-size fractions, under various atmospheric conditions, was investigated. The apparent kinetic results varied systematically with the sample and atmospheric conditions, accompanied by changes of the roles of surface reaction, diffusion of evolved water vapor from the reaction interface and gross diffusion of water vapor through the assemblage of sample particles.
- Koga, Nobuyoshi,Tanaka, Haruhiko
-
-
Read Online
- Fabrication of Zn(OH)2/ZnO nanosheet-ZnO nanoarray hybrid structured films by a dissolution-recrystallization Route
-
Zn(OH)2/ZnO nanosheet-ZnO nanoarray hybrid structured films were fabricated on F-doped SnO2-coated glass by a dissolution- recrystallization route without any additives. The as-deposited c-axis-oriented ZnO nanowhisker films were soaked in hot distilled water for various periods of time. X-ray diffraction, field-emission scanning electron microscopy, and transmission electron microscopy clarified that the dissolution of ZnO induced Zn(OH)2 to grow on the surface of the ZnO nanowhiskers film by heterogeneous nucleation and growth. The morphology of the Zn(OH)2 nanosheets was found to be controllable by the dissolution-recrystallization of as-deposited ZnO nanowhiskers in hot distilled water. ZnO with an almost identical morphology could also be produced by a dehydration reaction. Given the highly porous nature and the strong adsorption properties of the as-fabricated hybrid structured films, it is expected that they will have a variety of potential applications including dye-sensitized gas sensors and solar cells, and photocatalysis systems.
- Hu, Xiulan,Masuda, Yoshitake,Ohji, Tatsuki,Kato, Kazumi
-
-
Read Online
- Thermal stability of new zinc acetate-based complex compounds
-
The compounds were characterized by IR spectroscopy, chemical analysis and thermal analysis. Thermal analysis showed that no changes in crystallographic modifications of the compounds take place during (heating in nitrogen before) the thermal decompositio
- Gyoryova,Balek
-
-
Read Online
- On the reactivity of zinc hydroxide acetate dihydrate in ethanol
-
Zinc hydroxide acetate dihydrate, Zn5(OH)8(CH 3CO2)2·2H2O, reacts in ethanol at room temperature to yield a mixture of zinc oxide and anhydrous zinc acetate. The process is driven by dehydration of the starting salt. Dehydration of Zn5(OH)8(CH3CO2) 2·2H2O also occurs when it is heated in air, but the product obtained in that case depends on the heating rate, environment and temperature. For example, when it is kept in a sealed silica capillary at 100 °C, Zn5(OH)8(CH3CO2) 2·1.5H2O is formed after 15 min, whereas treatment in the range 90-100°C in an open environment results in the formation of anhydrous zinc hydroxide acetate. Heating of any of these products further causes their decomposition to Zn(CH3CO2)2 and ZnO. The coordination bonding mode of the acetate groups in the anhydrous layered zinc hydroxide acetate prepared by reaction with ethanol was studied by using solid-state NMR spectroscopy. The presence of chelating, unidentate and bidentate bridging modes for the carbonyl carbon atom was revealed, but there was no evidence for the inclusion of ethanol in the resultant structure. Therefore, the reaction in ethanol offers a convenient strategy to prepare anhydrous zinc hydroxide acetate and/or zinc oxide, because it avoids the sensitivity of the thermally induced dehydroxlation process to time, temperature and environment. Decomposition of zinc hydroxide acetate dihydrate in ethanol can be exploited to generate ZnO nanoparticles at room temperature. The mechanism involves the removal of waters of hydration and the formation of Zn5(OH)8(CH3CO2)2 followed by the generation of Zn(CH3CO)2 and ZnO. Copyright
- Moezzi, Amir,Cortie, Michael B.,Shimmon, Ronald,McDonagh, Andrew M.
-
-
Read Online
- Zn(II) carboxylates containing heterocyclic secondary ligands: synthesis and structure manifestation through DFT studies
-
New Zn(II) complexes (1–8) of general formula [Zn(R)2(L')2], where R = cinnamic acid (1–7), L' = 3-pyridine carboxamide (1), 2,2'-bipyridine (2), 3-pyridinecarbonitrile (3), 2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole (4), 2-methylimidazole (5), 2-phenylimidazole (6), 2-imidazolidinethione (7) and for (8), R = acetic acid; L' = 2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole)2, have been synthesized by a stoichiometric reaction between Zn(II) carboxylate(s) and the respective nitrogen-based ligands. The prepared compounds are analyzed by FTIR, NMR spectroscopy and single crystal X-ray diffraction techniques for their structural manifestations along with elemental analyses. The crystallographic data for 6 and 8 exhibit four-coordinated zinc having distorted tetrahedral molecular geometry. The thermogravimetric data demonstrate high stability of the compounds with gradual loss of acetate and thiadiazol fragments that ultimately lead to zinc oxide as the residual mass of 8. Quantum chemical calculations indicate that 7 is the softest in reactivity having the lowest band gap as determined from the energies of frontier molecular orbitals whereas 8 is highly polar with the highest dipole moment value of 12.61 D. The computational data are a complement to the success of the research.
- Zahoor, Ayesha,Imtiaz-Ud-Din,Andleeb, Sohaila,Raheel, Ahmad,Ayub, Rabia,Abbas, Sumaira,Tahir, Muhammad Nawaz
-
-
Read Online
- Stability of nonplanar N-methylporphyrins and their zinc complexes
-
Resistance of N-methyl-substituted porphyrins and their Zn(II) complexes to thermooxidative degradation and to the action of a DMSO-AcOH proton-donor solvent was studied by thermogravimetry and chemical kinetics. The fairly low stability of the complexes is caused by decreased planarity and, as a consequence, aromaticity of the macrorings and also by the tendency of the complexes to demethylation. The stability of the zinc complexes in AcOH varies in parallel with the degree of nonplanarity and resistance to thermooxidative degradation of their ligands. Pleiades Publishing, Inc., 2006.
- Berezin,Mis'ko,Antina,Berezin
-
-
Read Online
- A phosgene-free process for the synthesis of methyl N-phenyl carbamate by the reaction of aniline with methyl carbamate
-
A phosgene-free route for the synthesis of methyl N-phenyl carbamate (MPC) by the reaction of aniline with methyl carbamate in the presence of methanol was studied. Effects of catalysts, reaction temperature, reaction time, and catalyst content, the molar ratio of reactants and the content of water on the reaction were investigated. The results demonstrated that an aniline conversion of 90.1% and MPC selectivity of 99.7% were achieved when the reaction was carried out at 433 K for 4 h using ZnCl2 as a catalyst. A possible reaction mechanism was proposed based on the product distribution.
- Li, Qi-Feng,Wang, Jun-Wei,Dong, Wen-Sheng,Kang, Mao-Qing,Wang, Xin-Kui,Peng, Shao-Yi
-
-
Read Online
- Isolation and structural characterization of a binuclear intermediate species pertinent to transmetalation of Zn(salphen) complexes and the formation of polynuclear salen structures
-
Zinc(II) salphen complexes equipped with additional alkoxy donor groups at the 3-position of the salicylideneimine groups have been prepared to bind metal acetates in a second coordination sphere close to the central Zn(II) ion. The isolated binuclear mon
- Felices, Leire San,Escudero-Adan, Eduardo C.,Benet-Buchholz, Jordi,Kleij, Arjan W.
-
-
Read Online
- Controllable fabrication of various ZnO micro/nanostructures from a wire-like Zn-EG-AC precursor via a facile solution-based route
-
In this paper, ZnO particles with various morphologies were prepared though a facile solution-based route. The complexes Zn-EG-AC (EG: ethylene glycol; AC: CH3COO- groups) obtained by reaction of anhydrous zinc acetate and EG were used as precursors. It is found that the precursor could transform into ZnO in water with no need of assistant of additional alkali as it is sensitive to water. At the same time, it is well dispersed in reaction medium (water and ethanol). Experimental results showed that ZnO particles with various morphologies, such as the hexagonal rings, the hexagonal plates, the tubes, the prisms, and some interesting hierarchical structures, could be obtained by controlling hydrolysis of precursor in water and water/ethanol medium through finely tuning the experimental parameters. The success of shape-controllable fabrication was related intimately with the Zn-EG-AC precursor used in our synthesis.
- Tian, Chungui,Li, Wei,Zhang, Qi,Pan, Kai,Fu, Honggang
-
-
Read Online
- Zinc-67 NMR study of tetrahedral and octahedral zinc sites with symmetrical oxygen, nitrogen, and sulfur ligands
-
We report a 67Zn nuclear magnetic resonance (NMR) study of compounds containing zinc ions coordinated by oxygen, nitrogen, and sulfur ligands. New information concerning 67Zn nuclear quadrupole coupling constants (NQCC) and chemical shift was obtained from magic-angle spinning (MAS) spectra of solid compounds containing both natural abundance and enriched 67Zn isotopes. Rapid ligand exchange processes of [Zn(thiourea)4]2+ in aqueous solutions were also observed.
- Sham, Simon,Wu, Gang
-
-
Read Online
- Radiation-sensitive composition, pattern-forming method and radiation-sensitive acid generating agent
-
A radiation-sensitive composition includes: a first polymer having a first structural unit that includes an acid-labile group; and a first compound including a metal cation and a first anion that is a conjugate base of an acid. The acid has a pKa of no greater than 0. The acid is preferably sulfonic acid, nitric acid, organic azinic acid, disulfonylimidic acid or a combination thereof. The first compound is preferably represented by formula (1). In the formula (1), M represents a metal cation; A represents the first anion; x is an integer of 1 to 6; R1 represents a σ ligand; and y is an integer of 0 to 5, and a sum: x+y is no greater than 6. The van der Waals volume of the acid is preferably no less than 2.5×10?28 m3. [AxMR1y]??(1)
- -
-
-
- COMPACT AND HOMOGENEOUS QUANTUM DOTS AND METHODS OF MAKING THE SAME
-
The present disclosure provides quantum dots and methods of making the quantum dots comprising a substantially homogeneous population of monomeric nanocrystals, of a very small size, about 7 nm to about 12 nm in diameter. The method comprises mixing a nanocrystal coated with weakly binding ligands or ions with a polymer in a solution and incubating at a temperature greater than about 100° C., thereby forming a quantum dot having a substantially homogenous population of monomeric nanocrystals. The quantum dots can be further conjugated to bioaffinity molecules, enabling broad utilization of compact, biofunctional quantum dots for studying crowded macromolecular environments.
- -
-
-
- Oral Care Compositions and Methods of Use
-
Disclosed herein are oral care compositions including Zn:usnate complexes having a 1:2 zinc to usnate molar ratio. Methods of making and using the compositions are also provided.
- -
-
Paragraph 0104-0105
(2019/02/05)
-
- PERSONAL CARE COMPOSITIONS COMPRISING ZINC:USNIC ACID COMPLEXES AND METHODS OF USE
-
Disclosed herein are personal care compositions comprising Zn:usnate complexes having a 1:2 zinc to usnate molar ratio. Methods of making and using the compositions are also provided. The personal care compositions may include a cleansing component and an antibacterial component, wherein the antibacterial component comprises Zn:usnate complexes having a 1:2 zinc to usnate molar ratio.
- -
-
Paragraph 00082
(2019/02/06)
-
- Structurally diverse coordination compounds of zinc as effective precursors of zinc oxide nanoparticles with various morphologies
-
The structurally diverse coordination compounds of zinc were designed and synthesized using two types of building blocks: short-chain carboxylate ions and hexamethylenetetraamine. They were characterized by X-ray crystallography, infrared spectroscopy and thermal analysis. The studied compounds were used as precursors for production (via controlled thermal conversion) of zinc oxide nanoparticles. The conversion process was optimized in terms of two parameters (heating rate and maximum temperature). Such an approach, combined with proper design of the precursor structure, allows fabrication of various zinc oxide micro- and nanoparticles. The influence of a precursor structure and modifications of conversion parameters on size and morphology of ZnO particles were studied and discussed.
- Swiatkowski, Marcin,Kruszynski, Rafal
-
-
- Synthesis, stability, and electrocatalysis by Cu(II) and Zn(II) complexes of meso-bridged isomeric porphyrinoid tetraphenylporphycene
-
Spectral characteristics (electronic absorption spectra, fluorescence emission spectra, 1H NMR) of prepared Cu(II) and Zn(II) complexes of 2,7,12,17-tetraphenylporphycene {H2(β-Ph)4Por}, their thermal stability, and persis
- Berezin,Thao, Vu Thi,Guseinov,Shukhto,Berezina,Bazanov,Petrova,Semeikin
-
p. 688 - 694
(2017/06/09)
-
- The Induction Period and Novel Active Species in Zn(OAc)2 Catalyzed Synthesis of Aromatic Carbamates
-
Abstract: Zn(OAc)2 is known to exhibit excellent catalytic activity for aromatic carbamate synthesis by the reaction of aromatic amine and dimethyl carbonate (DMC). It is determined that an induction period exists during the synthesis of dimethyl-4,4′-methylenediphenyl dicarbamate (MDC) and methyl N-phenyl carbamate (MPC), although this period is more evident in the case of MDC. Zn(OAc)2 is able to catalyze the reaction of amine and DMC, but also react with DMC to form Zn4O(OAc)6, which also shows excellent catalytic activity for carbamate synthesis. As for MDC synthesis, Zn4O(OAc)6 plays the important role. However, Zn(OAc)2 plays the leading role in MPC synthesis. The deactivation of Zn4O(OAc)6 was also investigated. Zn4O(OAc)6 was initially transformed into Zn5(OH)8(OAc)2·2H2O (LHZA) and then into ZnO. Graphical Abstract: [Figure not available: see fulltext.].
- Li, Fang,Wang, Xi,Li, Hongqin,Wang, Shufang,Xue, Wei,Wang, Yanji
-
p. 1478 - 1484
(2017/08/29)
-
- General C-H Arylation Strategy for the Synthesis of Tunable Visible Light-Emitting Benzo[a]imidazo[2,1,5-c,d]indolizine Fluorophores
-
Herein we report the discovery of the benzo[a]imidazo[2,1,5-c,d]indolizine motif displaying tunable emission covering most of the visible spectrum. The polycyclic core is obtained from readily available amides via a chemoselective process involving Tf2O-mediated amide cyclodehydration, followed by intramolecular C-H arylation. Additionally, these fluorescent heterocycles are easily functionalized using electrophilic reagents, enabling divergent access to varied substitution. The effects of said substitution on the compounds' photophysical properties were rationalized by density functional theory calculations. For some compounds, emission wavelengths are directly correlated to the substituent's Hammett constants. Easily introduced nonconjugated reactive functional groups allow the labeling of biomolecules without modification of emissive properties. This work provides a straightforward platform for the synthesis of new moderately bright fluorescent dyes remarkable for their chemical stability, predictability, and unusually high excitation-emission differential.
- Lévesque, éric,Bechara, William S.,Constantineau-Forget, Léa,Pelletier, Guillaume,Rachel, Natalie M.,Pelletier, Joelle N.,Charette, André B.
-
p. 5046 - 5067
(2017/05/24)
-
- Facile synthesis and an effective doping method for ZnO:In3+ nanorods with improved optical properties
-
The sol-gel spin-coating method is usually used for thin-film deposition rather than to grow one-dimensional nanostructures. In this study, a novel regrowth method for spin-coated ZnO:In3+ films is demonstrated, using vapor-confined face-to-face annealing (VC-FTFA) in which a mica sheet is inserted between the two films prior to FTFA. ZnO:In3+ nanorods are regrown when indium chloride is used as the solvent because ZnCl2 and InCl3 vapors are generated and confined between the films. The near-band-edge emission intensity of the ZnO:In3+ nanorods resulting from VC-FTFA at 700 °C is enhanced by a factor of 17 compared with that of ZnO:In3+ films annealed in open air at the same temperature. Our method offers a simple and low-cost route for the fabrication of ZnO nanorods.
- Nam, Giwoong,Kim, Byunggu,Leem, Jae-Young
-
-
- Protolytic dissociation mechanisms and comparative acid stabilities of palladium(II), zinc(II), copper(II), and nickel(II) complexes of alkylated dipyrrins
-
Complexes of Pd(II), Cu(II), Ni(II), and Zn(II) with alkylated dipyrrins (Hdpm) were synthesized and characterized by physicochemical and spectroscopic methods. Protolytic dissociation kinetics of these complexes in benzene in the presence of acetic and trichloroacetic acid was studied. A protonated dipyrrin is the reaction product of protolytic dissociation of the complexes in acid solutions. The observed and true dissociation rate constants, as well as activation reaction parameters, were calculated. Kinetic models of the processes are proposed, and the patterns of influence of the ligand nature on dissociation kinetics were determined. The Pd(II) complexes proved to be much more stable than other those of the other metals, according to the results of the kinetic studies. The lability of the complexes strongly depends on the length and position of the alkyl substituent of the ligand. The dissociation of the Ni(II) complex gives a heteroligand complex at low concentrations of acid, but the complex undergoes full protolytic dissociation at higher concentrations of acid. The dissociation of the complex of Cu(II) is an equilibrium process, involving formation of the protonated form of the ligand.
- Rumyantsev, Evgeniy V.,Marfin, Yuriy S.
-
p. 699 - 704
(2014/08/18)
-
- Kinetic stability of complexes of some d-metals with 3,3'- bis(dipyrrolylmethene) in the binary proton-donor solvent acetic acid-benzene
-
The kinetics of dissociation of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) binuclear homoleptic double-stranded helicates with bis(2,4,7,8,9- pentametyldipyrrolylmethen-3-yl)methane (H2L) of the [M 2L2] composition
- Antina,Guseva,V'yugin,Antina
-
p. 1293 - 1297
(2013/01/14)
-
- Different geometrical arrangements in carboxylate coordination polymers of flexible dicarboxylic acid
-
Dicarboxylate coordination polymers (15) of Mn(II), Ni(II), Cu(II), Zn(II) and Cd(II), respectively, derived from (7-carboxymethoxy-naphthalen-2-yloxy)- acetic acid (L1H2) are synthesized and characterized. Depending on the coordination sites around the metal centers and coordination mode of the ligand, dimensionality of these polymers varies. The dicarboxylates adopt three spatial orientations: in-plane linear coordination, out-of-plane cis coordination and out-of-plane trans coordination mode. Both the cis and trans out-of-plane coordination modes are found to exist only if the ancillary ligand pyridine is coordinated to the metal ion. When the aquoligand coordinates the in-plane linear coordination mode of L1 predominates. The coordination polymers 4 and 5 show photoluminescence in solution. The dicarboxylate of (5-carboxymethoxy-naphthalen-1-yloxy)-acetic acid (L 2H2) does not form coordination polymer under ambient conditions, but prefers to remain as uncoordinated anion providing hydrophobic confinement to hexa-aquometal(II) cation. Compound 3 crystallizes in P2 1 space group and it shows broadband ultra-violet fluorescence centered at 352.9 nm on focusing 632.8 nm He:Ne laser.
- Deka, Himangshu,Sarma, Rupam,Kumari, Satchi,Khare, Alika,Baruah, Jubaraj B.
-
p. 1726 - 1734
(2011/09/20)
-
- Solvent dependence of the structure of ethylzinc acetate and its application in CO2/epoxide copolymerization
-
NMR and single-crystal X-ray diffraction experiments indicate that the ligand stoichiometry of the complexes formed from the reaction between zinc bis(acetate) and diethylzinc depends on the nature of the solvent (coordinating vs noncoordinating) and that the strength of the donor interaction of a coordinating solvent (THF vs pyridine) affects the nuclearity of the complex's repeat unit in the solid state. The complexes are active catalysts for the copolymerization of cyclohexene oxide and CO2, under mild conditions.
- Orchard, Katherine L.,Harris, Jonathan E.,White, Andrew J. P.,Shaffer, Milo S. P.,Williams, Charlotte K.
-
p. 2223 - 2229
(2011/05/11)
-
- Insights into a nontoxic and high-yielding synthesis of methyltrioxorhenium (MTO)
-
The versatile catalyst methyltrioxorhenium(VII) (MTO) is now available in high yields by utilizing easily accessible nontoxic starting materials. The new synthetic pathway allows an inexpensive, large-scale production of MTO, paving the way for industrial applications. A variety of starting materials is compared with respect to their applicability, availability and ease of handling. The reaction times and the by-products formed are compared under different reaction conditions. It was seen that silver perrhenate in combination with methylzinc acetate, which was derived from trimethylaluminum and zinc acetate, are the best starting materials for a high-yielding large-scale synthesis of MTO. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Mitterpleininger, Josef K. M.,Szesni, Normen,Sturm, Stefanie,Fischer, Richard W.,Kuehn, Fritz E.
-
p. 3929 - 3934
(2009/02/07)
-
- Effect of ligand nonplanarity and solvent nature on the kinetic stability of zinc porphyrin complexes
-
Planarity disturbance in metal porphyrin macrorings produces destabilization of complexes in dimethyl sulfoxide-acetic acid and benzene-acetic acid systems, except for cases where the coordination center is additionally stabilized by endocyclic substituents and/or extra ligands. The first dissociation stage of complexes with N-substituted analogs of porphyrins involves substitution of the acido ligand in the strongly shielded coordination sphere by an electron-donor solvent molecule. The revealed dependences of dissociation rate constants on acid concentration in DMSO, untypical of most metal porphyrins, are explained by a change in the type of the attacking species with changing solvent composition. The dissociation rate constants of complexes in an electron donor solvent can be lower by several orders of magnitude than in a weakly solvating medium.
- Berezin,Shukhto,Shatunov
-
p. 997 - 1004
(2008/12/21)
-
- Thermal, spectral and biological properties of Zn(II) complex compounds with phenazone
-
The thermal decomposition of the complexes Zn(form)2 2phen (I), Zn(ac)2 2phen (II), Zn(prop)2 2phen (III), Zn(but) 2 2phen (IV), where phen=phenazone, form=formiate, ac=acetate, prop=propionate, but=butyrate has
- Szunyogova, Erika,Gyoeryova, Katarina,Hudecova, Daniela,Piknova, Lenka,Chomic,Vargova, Zuzanna,Zelenak
-
p. 219 - 223
(2008/10/09)
-
- Insertion of carbon dioxide into (PCP)PdII-Me bonds
-
A (PCP)PdMe complex has been synthesized and structurally characterized, displaying a very long Pd-Me bond. It is reactive toward CO2 insertion, giving the corresponding acetate in quantitative yield. The methyl complex can be regenerated using ZnMe2, and catalytic carboxylation is possible in benzene.
- Johansson, Roger,Jarenmark, Martin,Wendt, Ola F.
-
p. 4500 - 4502
(2008/10/09)
-
- Kinetics of the Dissociation of Transition Metal Complexes with α,α-Dipyrrolylmethene in Acetic Acid-Benzene as a Binary Proton-Donating Solvent
-
The kinetics of the dissociation of Co(II), Ni(II), and Zn(II) complexes with 4,4′-dibutyl-3,3′,5,5′-tetramethyldipyrrol-2,2′- ylmethene was studied in acetic acid-benzene as a binary proton-donating solvent. The metal nature was found to affect the kinetic parameters of the process. Assumptions were made about the limiting step of the process and the effectiveness of d metal ions in the template synthesis of porphyrins from dipyrrolylmethenes.
- Guseva,Antina,Berezin
-
p. 690 - 693
(2008/10/08)
-
- Phosphoraneiminato acetate cluster of copper and zinc. Crystal structures of [Cu4(NPEt3)2(O2CCH3) 6] and [Zn4(NPEt3)2(O2CCH3) 6]
-
The anhydrous acetates of copper(II) and zinc react with the silylated phosphaneimine Me3SiNPEt3 in dichloromethane at 20 °C forming the mixed phosphoraneiminato acetate clusters [Cu4(NPEt3)2(O2CCH3) 6] (1), which forms emerald crystals, and colourless [Zn4(NPEt3)2 · (O2CCH3)6] (2). In spite of analogous composition the structures of 1 and 2 are completely different. In the asymmetric unit of 1 three copper atoms of an almost isosceles triangle are linked via two nitrogen atoms of the NPEt3- groups to form a trigonal bipyramidal aggregate. One of these three copper atoms is chelated by an acetate group, another one is connected with the fourth copper atom via three μ2-O2C-CH3 groups. The asymmetric units are associated via a μ2-O2C-CH3 group and a μ3-OC(O)CH3 group at a time so that infinite chains result. In 2 two zinc atoms are linked via the nitrogen atoms of the two NPEt3- groups to form an almost centrosymmetric four-membered ring. Both nitrogen atoms of the four-membered ring are connected with another zinc atom each. These zinc atoms again are linked with the zinc atoms of the Zn2N2 four-membered ring via two μ2-O2C-CH3 groups each and additionally coordinated with a terminal acetate ligand each.
- Ackermann, Hartmut,Weller, Frank,Neumueller, Bernhard,Dehnicke, Kurt
-
p. 147 - 152
(2008/10/08)
-
- Vibrational spectra and structures of zinc carboxylates II. Anhydrous zinc acetate and zinc stearate
-
A normal mode analysis was carried out for a monoclinic anhydrous zinc acetate crystal in which the acetate groups had bridging bidentate coordination forms, and spectral assignments were made. Based on the assignments, a relation between the coordination structure of the carboxylate groups around the zinc atom and the vibrational frequencies of the carboxylate rocking mode was found. This relation was applied to zinc stearate to determine its coordination form, and we found that zinc stearate had a bridging bidentate form.
- Ishioka, Tsutomu,Shibata, Youko,Takahashi, Mizuki,Kanesaka, Isao
-
p. 1811 - 1818
(2007/10/03)
-
- Influence of the spatial structure of the alkyl chain on the composition of the product of the direct neutralization reaction between aliphatic carboxylic acids and zinc hydroxide
-
A study was launched to clarify the influence of the spatial structure of the alkyl chain on the products of the direct neutralization reactions between zinc hydroxide and several non-cyclic saturated carboxylic acids in the presence of an excess of either the carboxylic acid or zinc hydroxide. The species formed were identified on the basis of their FT-IR spectra in the mid-IR region. Straight-chain acids produced the corresponding zinc bis-carboxylates with polymeric sheet structure under all circumstances. The species present in the products of the branched-chain carboxylic acids depended strongly on the nature of the component in excess and the bulk of the alkyl group. Besides the starting materials the reaction mixtures contained two carboxylate species in various ratios. One of them was the zinc bis-carboxylate of the branched-chain carboxylic acid, characterized by an additional νC=O band at around 1630 cm-1, above the usual two strong carboxylate stretching bands. The other species was the corresponding complex Zn4O(RCOO)6. The conditions of formation of these three forms of zinc carboxylates were formulated on the basis of the decreasing possibility of interaction between the neighbouring alkyl chains to form a polyethylene subcell in the sequence of: Zn(RCOO)2 (polymeric sheet) > Zn(RCOO)2 (intermediate form) > Zn4O(RCOO)6 (tetranuclear complex).
- Dreveni,Berkesi,Andor,Mink
-
-
- Reduction of Arylcarbonyl Using Zinc Dust in Acetic Acid
-
Zinc dust in acetic acid has been found to be a versatile and chemoselective reagent for the reduction of various arylcarbonyls to the corresponding alcohols or their acetates in fair yields.
- Rani, B. Radha,Ubukata, Makoto,Osada, Hiroyuki
-
p. 282 - 284
(2007/10/02)
-
- Clusters as ligands. Comparison of the reactivity of (CO)9Co3(μ3-CR) (R = COOH, P-C6H4(CH2)2COOH) leading to the formation of Zn[p-C6H4(CH2)2CO2] 2 vs MII4O[(CO)9Co3CCO2] 6 (M = Zn, Co)
-
In order to explore the notion of cluster-substituted ligands as a route to large cluster assemblies, the gram-scale synthesis and purification along with spectroscopic and crystallographic characterization of two cluster-substituted carboxylate ligand precursors, (CO)9Co3{μ3-C[1,4-C6H 4(CH2)2COOH]}, I, and (CO)9Co3(μ3-CCOOH), II, were carried out [I-toluene, space group triclinic P1, a = 9.348(1) A?, b = 11.954(1) A?, c = 13.862(1)A?, α = 92.83(2)°, β = 100.67(2)°, γ = 109.51(1)°, V = 1424.3 A?3, d(calcd) = 1.59 g/cm3, Z = 2; II, space group triclinic P1, a = 7.906(1) A?, b = 8.673(1) A?, c = 12.915(4) A?, α = 83.73(2)°, γ = 86.94(2)°, γ = 68.30(1)°, V = 817.8 A?3, d(calcd) = 1.98 g/cm3, d(obs) = 1.97 g/cm3, Z = 2]. Although the spectroscopic characterization of II has been previously reported, its instability in solution at room temperature has not been recognized. Thus, we report its spontaneous conversion to Co4O[(CO)9Co3CCO2]6, III, which is a metal cluster analogue of classical MII4O[RCO2]6 basic metal carboxylates normally formed by sublimation of MII[RCO2]2. The reaction of I, which is stable in solution, with 1/2 ZnEt2 yields Zn[(CO)9Co3CC6H4(CH 2)2CO2]2, which is analogous to the product formed from either acetic acid or C6H5(CH2)2COOH with the same reaction stoichiometry. In contrast, the reaction of II with ZnEt2 in a 1:1 stoichiometry forms Zn4O[(CO)9Co3CCO2]6, IV, in high yield at room temperature. The differing chemistry of II is attributed to the direct electronic interaction of the tricobalt cluster with the carboxylate fragment in II. IR spectra and cyclic voltammetry are used to detail the nature of this electronic coupling. Although both III and IV undergo quasi-reversible cluster ligand dissociation in THF, the reaction is more extensive for the former compound and ultimately leads to degradation of the tricobalt cluster.
- Cen, Wei,Haller, Kenneth J.,Fehlner, Thomas P.
-
p. 995 - 1000
(2008/10/08)
-
- Ultrasonic Absorption Study of the Complex Formation of Zinc(II) Carboxylates in Aqueous Solution
-
Ultrasonic absorption of aqueous zinc(II) formate, acetate, and propionate is measured in the metal-rich concentration regions with a pulse technique over the frequency range 3-260 MHz.The single relaxations observed in all cases are attributed to the complex formation of zinc(II) carboxylates via the Eigen-Tamm mechanism of stepwise association.The reaction parameters are determined from the concentration dependences of the relaxation frequency and amplitude.Both the association constant of outer-sphere complex and the rate constant of ligand substitution indicate ligand dependences; the former is larger while the latter is smaller with the higher carboxylate.However, the uncertainties involved in these reaction parameters prevent the elucidation of the above feature.The volume changes of the outer-sphere complexing are substantially less than those of the ligand substitution; the volume change of the latter is larger for the higher carboxylate.
- Tamura, Kiyoshi
-
p. 7358 - 7362
(2007/10/02)
-
- Coordination properties of sterically hindered porphyrins and metal porphyrins
-
The detailed mechanism of the coordination reactions of porphyrins has been established by a study of the kinetics of complex formation of sterically hindered porphyrins with copper, zinc, and cadmium acetates in pyridine and in dimethylformamide, and also of the kinetics of the solvoprotolytic dissociation of the zinc and manganese complexes.The role of spatial shielding in the formation and dissociation reactions of sterically hindered porphyrins is discussed.
- Golubchikov, O. A.,Lomova, T. N.,Kuvshinova, E. M.,Korovina, S. G.,Klyueva, M. E.,et al.
-
p. 188 - 192
(2007/10/02)
-
- SYNTHESIS OF Cu(II) AND Zn(II) AMINOCARBOXYLATES AND THEIR PROPERTIES.
-
It was established by methods of chemical analysis, IR spectroscopy, and thermogravimetry that the reaction of Cu(II) and Zn(II) carboxylates of the corresponding monobasic aliphatic acids with gaseous ammonia in dimethylformamide leads to realization of coordination compounds of composition Cu(RCOO)//2 multiplied by (times) 2NH//3, Zn(CH//3COO)//2 multiplied by (times) 2NH//3.
- Prisyazhnyuk,Dzhambek
-
-
- The Solvation of Cobalt(II) and Zinc(II) Acetates in Dioxan-Hexane and Tetrahydrofuran-Hexane Mixtures
-
The state of cobalt(II) and zinc(II) acetates in dioxan-hexane and tetrahydrofuran-hexane mixed solvents has been investigated by solubility and spectrophotometric methods at 298.15 K.It is shown that the acetates exist in dioxan and tetrahydrofuran as tetrahedral complexes with a solvation number of 2.The stability constants of these complexes have been calculated.
- Kazakova, I. M.,Golubchikov, O. A.,Berezin, B. D.
-
p. 476 - 478
(2007/10/02)
-
