Bis Zinc Research Articles

Zinc‐Mediated Formation of Trifluoromethyl Ethers from Alcohols and Hypervalent Iodine Trifluoromethylation Reagents

A (fluor)ry of activity: The transfer of an intact trifluoromethyl group from a hypervalent iodine reagent to an aliphatic alcohol occurs smoothly upon activation by zinc bis(triflimide). This constitutes a straightforward method for the preparation of trifluoromethoxy alkyl derivatives, compounds otherwise difficult to access.

Raman spectral investigation of thiourea complexes

Spectroscopic properties of metal complexes of thiourea single crystals (tris thiourea zinc acetate, bis thiourea cadmium zinc acetate and bis thiourea ammonium chloride) which are non-linear optic materials were investigated by Raman scattering spectroscopy. The vibrational frequencies of the functional groups are identified and assigned. Effects due to the coordination of thiourea with metal ions are analyzed. Hydrogen bonding interactions involved in the metal complexes are observed in the Raman spectra.

Room temperature ferromagnetism in nanocrystalline Ni-doped ZnO synthesized by co-precipitation

Ni-doped ZnO powder was synthesized by thermal co-decomposition of a mixture of bis(acetylacetonato) zinc(II)hydrate and bis(dimethylglyoximato)nickel(II) complexes. The samples were characterised by X-ray diffraction (XRD), Energy dispersion X-ray fluorescence (EDXRF), and FT-IR spectroscopy. The atomic ratio Ni/Zn of the samples was determined by the EDXRF method to be 1%, 4.3%, 7.4% and 22.5 wt%. The XRD studies show the formation of nanocrystalline (14–18 nm) of Ni-doped ZnO along with nanoparticles of NiO. By magnetic measurements, it was observed that powder contains 1%Ni, 4.3%Ni, 7.4%Ni exhibits superparamagnetic behaviour while the sample of 22.5%Ni prepared in closed atmospheric environment shows clear ferromagnetic (FM) loop at room temperature due to the formation of solid solution Zn 1− x Ni x O.

Synthesis and structures of complexes with axially chiral isoquinolinyl-naphtholate ligands

The synthesis of axially chiral ligands 1-(3',6'-di-t-butyl-2'-hydroxy-1'-naphthyl)-3-R-isoquinoline (R = H, Pr(i), Bu(t)) (LR-H) is described. Ligands with unsubstituted isoquinolinyl rings tend to give 1:2 metal complexes. The syntheses and crystal structures of Li2(LH)2(THF)2 (9), (LH)2Ti(OPr(i))2 (12), Zn(LH)2 (13) and [Mg(LH)2]2 (14) are reported. Complex formation is highly stereoselective; the ligands in 1:2 complexes have the same stereochemistry (i.e. R,R and S,S but not R,S), whereas in the binuclear magnesium compound 14 the bridging and non-bridging ligands LH have opposite stereochemistry. The reaction of LH-H with Pd(acac)2 afforded the N,O chelate Pd(acac)(LH) (10), whereas towards K2PtCl4 the same ligand acts as an N-donor only, to give trans-PtCl2(LH-H)2 (11) in which the OH groups are hydrogen-bonded to one of the two chloride ligands. The more bulky ligand with a t-butyl substituent in the 3-position of the isoquinolinyl ring reacts with zinc and magnesium bis(amides) to give the mixed-ligand species (LBu)ZnN(SiMe3)2 and (LBu)MgN(SiMe3)2, respectively, which catalyse the ring-opening polymerisation of epsilon-caprolactone (CL) and rac-lactide (LA).

The Studies of Conditions for Inducing Chirality to Cu(II) Complexes by Chiral Zn(II) and Ni(II) Complexes with Schiff Base

Recently, we have discovered that some chiral Schiff‐base nickel(II) complexes induced d‐d bands of CD spectra of some achiral copper(II) complexes. However, the novel phenomenon could be observed only a few systems of hybrid materials or limited conditions so far. In order to test conditions about copper(II) ions, we investigated model systems (1) metal‐dendrimer (Cu‐PAMAM; G4‐NH2 terminal) containing relatively small amount of copper(II) ions (4.5 equivalent to PAMAM) for modeling separated systems of achiral copper(II) complex from chiral Schiff‐base nickel(II) or zinc(II) complexes, Bis(N‐R‐1‐naphtylethyl‐3,5‐dichlorosalicydenaminato)nickel(II) or zinc(II) by polymer matrix. (2) equilibrium of copper(II) N‐ethylethylenediamine complexes to measure absorption spectra of d‐d band, pH, and electron conductivity during titration of copper(II) ions. The results showed that (1) 4.5Cu‐PAMAM could not be induced their d‐d bands by the chiral nickel(II) or zinc(II) complexes, which suggested that separation by polymers prevented from inducing CD peaks. (2) Although 36Cu‐PAMAM was known, uncoordinated copper(II) ions excess to ligands mainly attributed to increase electron conductivity by remained ions in methanol solutions, which was not associated with intermolecular interaction or dipole moments being effective for the induced CD mechanism by using molecular recognition between neutral molecules of metal complexes.

Metal-Containing Proteins, Macrocycles, and Coordination Complexes in Therapeutic Applications and Disease

Treatment of diseases with natural and synthetic materials has been an aspiration of mankind since the dawn of human development. From the use of willow-bark to the marketing of aspirin, a steady move from folk remedies to the use of chemistry and biology to develop new therapies has been observed. In terms of metal-containing drugs, the platinum-containing drug cisplatin has long been the most effective metal-containing anticancer drug on the market. However, severe side effects of conventional drugs are associated with the inability to distinguish between healthy and cancer cells. Hence, a concerted world-wide effort is in progress to discover and characterise new drugs that may distinguish between healthy and cancer or other diseased cells. New techniques of drug delivery are sought and the use of natural products, proteins, antibodies, and synthetic polymers as drug delivery devices capable of targeting a diseased site is being investigated. These issues are nicely illustrated by macrocycles such as porphyrins, phthalocyanines, and related systems. Some of these compounds exhibit selective absorption by cancer cells and have the ability to photosensitize formation of singlet oxygen. These attributes have led to the development of alternative cancer treatments known as photodynamic therapy. Sadly, many potentially good new therapeutic agents often never leave the designers' laboratory due to some pharmacological problems associated with its in vivo use. The use of drug delivering devices, including water-soluble synthetic polymeric drug delivery systems, may help overcome many pharmacological drug-related problems, including those of solubility, specificity, and biocompatibility, factors that currently prevent many potentially good therapeutic agents from reaching clinics. The focus of this special issue is the synthesis, characterisation, physical studies, and application of synthetic metal-containing complexes and natural occurring proteins in serious human diseases such as cancer, diabetes, arthritis, viral disease, malaria, and tuberculosis with special focus on the following: porphyrins, phthalocyanines, and related complexes in photodynamic cancer therapy; proteins, enzymes, and synthetic polymeric drug delivery systems in the treatment of cancer and other diseases; coordination and organometallic compounds in cancer, arthritis, malaria, and viral disease. Towards these goals, L. Josefsen and R. Boyle describe in their review article the development and application of metal-based photosensitisers, including porphyrins and phthalocyanines, in photodynamic therapy. Four other publications highlight different aspects of porphyrin-based macrocyclic photosensitisers. S. Lee et al. focus on the cellular uptake and toxicity of thiotetra (ethylene glycol) monomethyl ether-functionalized porphyrazines. J.-Y. Liu et al. focus on in vitro photodynamic activity of novel amphiphilic zinc(II) phthalocyanines bearing oxyethylene-rich substituents. E. Antunes and T. Nyokong highlight the syntheses and photophysical properties of tetraazatetrabenzcorrole photosensitizers. Sakamoto et al. present a fundamental study of zinc bis(1,4-didecylbenzo)-bis(2,3-pyrido)porphyrazine for application in photodynamic therapy of cancer. Considering polymeric drug delivery systems, South African E. Neuse's excellent review describes the use of synthetic polymers as metal-containing drug delivery vehicles in medicine. M. David Maree et al. provided a fine treatise on why biocompatible synthetic polymeric drug delivery systems are becoming increasing popular as drug delivering devices. They also demonstrate the principles behind these systems in a practical study utilising ferrocene and phthalocyanine derivatives anchored on a water-soluble polymeric drug carrier derived from lysine and aspartic acid. Italians Longo and Vasapollo demonstrated the use of phthalocyanine-based molecularly imprinted polymers as nucleoside receptors. X. Sun et al. report on the identification of proteins related to nickel homeostasis in Helicobater pylori by immobilized metal affinity chromatography and two-dimensional gel electrophoresis. P. Nagababu reported DNA-binding and photocleavage studies of cobalt (III) ethylenediamine pyridine complexes. M. Blackie and K. Chibale's excellent minireview focuses on metallocene antimalarials. The development of new metal-containing chemotherapeutic drugs is highlighted by contributions from M. Hogan et al. in their synthetic and cytotoxic study of new titanocene analogous. S. Mahepal et al. look at the in vitro antitumor activity of novel, mitochondrial-interactive, gold-based lipophilic cations. Sathisha et al. describe bis-isatin thiocarbohydrazone metal complexes and their antitumor activity against Ehrlich Ascites Carcinoma in Swiss albino mice. In conclusion, J. M. Botha and A. Roodt report mechanistic studies on trans-aquatetracyanooxo complexes of Re(V) and Tc(V) and discuss the implications of their results for nuclear medicine. We hope that this special issue will stimulate new research in all areas of metal-containing drug research and that it will help to focus research efforts of new and experienced researchers on key problems in the exciting field of metal-containing drug research. Jannie C. Swarts Michael J. Cook Edward N. Baker

Analytical strategy for rapid identification and quantification of lubricant additives in mineral oil by high-performance thin-layer chromatography with UV absorption and fluorescence detection combined with mass spectrometry and infrared spectroscopy.

A simple strategy for identification and quantification of lubricant additives in mineral oil was demonstrated by high-performance thin-layer chromatography with UV absorption and fluorescence detection using various coupling options, e.g., with attenuated total reflectance infrared (ATR-IR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and direct analysis in real-time mass spectrometry (DART-MS). For the additives zinc bis(O,O'-diisobutyl dithiophosphate), zinc bis(O,O'-didodecyl dithiophosphate), and Anglamol 99, 2 chromatographic systems were developed, i.e., a reversed-phase (RP) system on RP2 plates using an acetonitrile-based mobile phase and a normal-phase system on silica gel 60 plates using a toluene-based gradient. Densitometry was performed by absorption measurement at 220 nm. Repeatabilities (relative standard deviation, n = 6) between 2.2 and 5.5% and correlation coefficients >0.9973 were highly satisfactory for the analysis of these additives in the mineral oil. Primuline reagent was used to improve the detection limit of the lipophilic additives by a factor of 2, followed by fluorescence measurement at UV 366/>400 nm. For rapid identification by ATR-IR and FTIR, the respective additive zones on the plate were online extracted by an interface called ChromeXtract, concentrated, and directly applied for measurements in the wave number range of 4000-400 cm(-1). Identification was confirmed by online ESI-MS within a minute using ChromeXtract and by DART-MS within seconds.

High-contrast fluorescence switching using a photoresponsive dithienylethene coordination compound

A novel hybrid system ( Zn4) containing a zinc bis(acylamidine) fluorescent dye covalently decorated with two photochromic dithienylethene (DTE) structures was prepared using a concise synthetic route. The photoregulated quenching of the fluorescence from the metal complex was achieved by reversibly switching the DTE component between its two isomers using UV and visible light. The fluorescence quenching can be attributed to intramolecular energy transfer, electron transfer or a combination of the two. Either process is only possible when the DTE is in its ring-closed form ( Zn4b). The ring-open counterpart ( Zn4a) lacks an absorption band in the visible region of the spectrum to accommodate energy transfer from the metallobis(acylamidine) to the photochromic DTE, and has an oxidation potential that is too large to match the reduction potential of the metal complex making electron transfer thermodynamically unfavourable. UV–vis absorption and emission spectroscopy demonstrated that the photoregulation of fluorescence has little effect on the photochromic process and the fluorescence could be turned “on” and “off” several times without the appearance of notable side products. The high contrast ratio (∼100:1) between the bright and dark states combined with the excellent thermal bistability make the hybrid an excellent candidate for potential use in non-destructive read-out and biological labeling applications, although several limitations need to be overcome (speed of photoswitching, and stability and solubility in water).

Investigation of Zinc bis(1,4-didecylbenzo)-bis(2,3-pyrido) Porphyrazine for Application as Photosensitizer in Photodynamic Therapy of Cancer.

The phthalocyanine analogue containing nonperipheral long alkyl-substituted benzenoid rings and pyridine rings, zinc bis(1,4-didecylbenzo)-bis(2,3-pyrido) porphyrazine, was synthesized. Zinc bis(1,4-didecylbenzo)-bis(2,3-pyrido) porphyrazine reacted with dimethyl sulfate and monochloroacetic acid to produce their quaternized products and diethyl sulfate to produce the sulfo-substituted products. All quaternized and sulfo-substituted showed amphiphilic character. Identical peaks in cyclic voltammograms appeared for these products before and after quaternization. During the evaluation of zinc bis(1,4-didecylbenzo)-bis(2,3-pyrido) porphyrazine for its photodynamic therapy of cancer (PDT) efficacy by cancer cell culture, the light exposed dimethyl sulfate quaternized zinc bis(1,4-didecylbenzo)-bis(2,3-pyrido) porphyrazines in IU-002 cells produce cell disruption that can be detected as a decrease in fluorescence.

Investigation of zinc bis(1,4-didecylbenzo)-bis(2,3-pyrido) porphyrazine as an efficient photosensitizer by cyclic voltammetry

The phthalocyanine analogue containing non-peripheral, long alkyl-substituted benzenoid rings and pyridine rings, zinc bis(1,4-didecylbenzo)-bis(2,3-pyrido)porphyrazine was synthesized. The synthesized product is an interesting compound because quaternization of the pyridine nitrogen is expected to impart cationic amphiphilic character. Zinc bis(1,4-didecylbenzo)-bis(2,3-pyrido)porphyrazine was reacted with dimethyl sulfate and monochloroacetic acid to produce the quaternized products and with diethyl sulfate to produce the sulfo-substituted product; all such compounds displayed amphiphilic character. Identical peaks in cyclic voltammograms were obtained for the products before and after quaternization. Zinc bis(1,4-didecylbenzo)-bis(2,3-pyrido)porphyrazine had no changes in its reduction or oxidation properties compared to phthalocyanine analogues.

Bis(guanidine)]zinc Complexes and Their Application in Lactide Polymerisation

AbstractThe bis(guanidine)‐stabilised zinc complexes [N1,N2‐bis(1,3‐dimethylimidazolidin‐2‐ylidene)ethane‐1,2‐diamine]dichloridozinc(II), [Zn(DMEG2e)Cl2] (C1), diacetato[N1,N2‐bis(1,3‐dimethylimidazolidin‐2‐ylidene)ethane‐1,2‐diamine]zinc(II),[Zn(DMEG2e)(CH3COO)2] (C2), and bis[N1,N2‐bis(1,3‐dimethylimidazolidin‐2‐ylidene)ethane‐1,2‐diamine]zinc(II) bis(trifluoromethanesulfonate), [Zn(DMEG2e)2](CF3SO3)2(C3), have been synthesised and completely characterised by means of X‐ray structure analysis, NMR spectroscopy and mass spectrometry. These [bis(guanidine)]zinc complexes were investigated regarding their activity in the bulk polymerisation ofD,L‐lactide. It could be shown that these compounds are able to act as initiators for lactide polymerisation, and polylactides with molecular weights (Mw) of around 18000–59000 g/mol could be obtained. Variation of the reaction temperature revealed that the molecular weights decrease with increasing temperature. Additionally, the correlation of the intrinsic viscosity with the molecular weight demonstrates that the obtained polymers are linear and structurally homogeneous.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Diamagnetic 8-amidoquinoline and 8-(trialkylsilylamido)quinoline complexes of divalent nickel and zinc

Transamination of Zn[N(SiMe 3) 2] 2 with 8-(triisopropylsilylamino) ( 1a) and 8-(tert-butyldimethylsilylamino)quinoline ( 1b) yields monomeric heteroleptic bis(trimethylsilyl)amido zinc 8-(trialkylsilylamido)quinoline ( 2a, 2b). The reaction of Zn[N(SiMe 3) 2] 2 with 8-aminoquinoline leads to the formation of heteroleptic dimeric 8-amidoquinoline zinc bis(trimethylsilyl)amide ( 3). This compound shows fluxionality on the NMR time scale due to a transannular trans– cis isomerization process and also a strong temperature dependency of the ratio of these two isomers. Variation of the stoichiometry allows the synthesis and isolation of homoleptic zinc bis(8-amidoquinoline) ( 4) with the zinc atoms in a distorted tetrahedral environment. The metallation of 8-aminoquinoline with (tmeda)NiMe 2 yields diamagnetic nickel bis(8-amidoquinoline) ( 5) with a nickel center showing a distorted square planar coordination sphere. Dinuclear zinc complexes are accessible employing tetra-dentate di(8-aminoquinolyl)diphenylsilane ( 6). The metallation of 6 with dimethylzinc yields dimeric zinc di(8-amidoquinolyl)diphenylsilane ( 7) with tetrahedrally coordinated zinc atoms. A comparison of the molecular structures of 1a, 2b, 3, 4, 5, 6, and 7 shows nearly no dependency of the structural data of the quinolyl unit on the substitution pattern of the amino function. The metal–nitrogen bond lengths depend on the coordination numbers of the metal and the nitrogen atoms (terminal or bridging position) as well as the electrostatic attraction between the metal cations and the amino bases.

Structural and Mechanistic Studies of Bis(phenolato)amine Zinc(II) Catalysts for the Polymerization of ε-Caprolactone

The syntheses, characterization, epsilon-caprolactone (CL) polymerization activity, and kinetics investigation of two zinc(II) bis(phenolato)amine complexes L2Zn2 are reported (L = methylamino-N,N-bis(2-methylene-4,6-di-tert-butylphenolato) and/or methylamino-N,N-bis(2-methylene-4-adamantyl-6-tert-butylphenolato)). X-ray crystallographic and 1H NMR studies, including NOESY and PGSE experiments, provided insight into the solid and solution state structures, respectively, as well as evidence for the catalytically active species responsible for the ring-opening polymerization of CL. Additionally, solution polymerizations and kinetic experiments involving (L1)2Zn2 in the presence of benzyl alcohol (BnOH) were performed to elucidate the influence of catalyst structure, solvent, and the concentration dependence of the catalytically active species, CL, and BnOH on the rate and control of poly-epsilon-caprolactone (PCL) formation. The structural, polymerization, and kinetic data support equilibria involving both mononuclear and dinuclear forms of (L1)2Zn2 as well as a monomer-activated route to PCL.

An unprecedented two-dimensional polymeric [Zn(OOC–C 6H 4–COO) 2] n2−[ +H 3N–(CH 2) 3–NH 3+] n system bearing one-dimensional chain of zinc(II) bis(phthalate) dianions held by propane-1,3-diammonium cations: Crystal structure, thermal and fluorescent properties

A novel zinc(II) phthalate compound, [Zn{C 6H 4(COO) 2} 2] n 2−[NH 3–(CH 2) 3–NH 3] n 2+, 1 which contains four different phthalate moieties coordinated to the Zn(II) ion through one each of their carboxylate moieties in a η 1-form and each phthalate moiety acting as a bridging unit with an overall tetrahedral geometry around the metal ion has been prepared and structurally characterized. The structure is unique in the sense that the dianionic moieties [Zn{C 6H 4(COO) 2} 2] 2− form an infinite one-dimensional network composed of 14-membered cyclic units interconnected in a way that they are disposed alternatively in almost perpendicular planes. The dicationic [NH 3–(CH 2) 3–NH 3] 2+ units are seen to hold these one-dimensional chains by strong coulombic and hydrogen bond interaction, resulting in an infinite two-dimensional layered structure of 1. The compound is thermally stable up to 250 °C. Above this temperature it loses one equivalent of phthalate moiety along with the diammonium unit to yield Zn(II) phthalate. The thermodynamic and kinetic parameters associated with this process could be evaluated using Coats–Redfern equation which shows the activation energy E a for the process as 305.0 kJ mol −1, the frequency factor A as 1.49 × 10 11 s −1 and the entropy change Δ S as −35.90 JK −1 mol −1. Fluorescent emission properties of 1 was studied by exciting the compound at 380 nm and also at 322 nm which were found to be the two λ max corresponding to absorptions of the molecule. Interestingly, the compound gave same type of emission spectra showing a maximum around 444 nm on exciting at these two different wavelengths, indicating that the molecule comes to the first excited state from the higher excited state by a fast non-radiative process before it exhibits singlet emission to come to the ground state.

New bimetallic compounds based on the bis(thiosemicarbazonato) motif

Zinc and copper bis(thiosemicarbazonato) complexes containing more than one metal centre have been prepared with a view to examining their application for molecular imaging. The zinc complexes are fluorescent with excitation and emission at relatively long wavelengths. The dinuclear copper complex undergoes two sequential, quasi-reversible reductions.

Functionalized Bis(thiosemicarbazonato) Complexes of Zinc and Copper: Synthetic Platforms Toward Site-Specific Radiopharmaceuticals

Two new types of unsymmetrical bis(thiosemicarbazone) proligands and their neutral zinc(II) and copper(II) complexes have been synthesized. These bifunctional ligands both chelate the metal ions and provide pendent amino groups that can be readily functionalized with biologically active molecules. Functionalization has been demonstrated by the synthesis of three water-soluble glucose conjugates of the new zinc(II) bis(thiosemicarbazonato) complexes, and their copper(II) analogues have been prepared in aqueous solution via transmetalation. A range of techniques including NMR, electron paramagnetic resonance, cyclic voltammetry, high-performance liquid chromatography (HPLC), UV/vis, and fluorescence emission spectroscopy have been used to characterize the complexes. Four compounds, including two zinc(II) complexes, have been characterized by X-ray crystallography. The connectivity and conformation of the glucose conjugates have been assigned by NMR spectroscopy. Time-dependent density functional theory calculations have been used to assign the electronic transitions of the copper(II) bis(thiosemicarbazonato) chromophore. Two copper-64-radiolabeled complexes, including one glucose conjugate, have been prepared and characterized using radio-HPLC, and transmetalation is shown to be a viable method for radiolabeling compounds with copper radionuclides. Preliminary cell washout studies have been performed under normoxic conditions, and the uptake and intracellular distribution have been studied using confocal fluorescence microscopy.

Systemic Effects of Orally-Administered Zinc and Tin (IV) Metalloporphyrins on Heme Oxygenase Expression in Mice

Some metalloporphyrins (Mps) inhibit heme oxygenase (HO), the rate-limiting enzyme in the production of bilirubin, and are potential compounds for the treatment of neonatal jaundice. We studied the safety and efficacy of Mps following oral administration. Adult HO-1-luc reporter mice were administered 30 micromol/kg body weight of tin mesoporphyrin (SnMP), zinc bis glycol deuteroporphyrin (ZnBG), or zinc protoporphyrin (ZnPP), or vehicle by oral gavage. Bilirubin production was measured as total body carbon monoxide (CO) excretion (VeCO). HO activity was quantitated via CO measurements by gas chromatography. HO-1 protein was determined by Western blot. HO-1 transcription levels were assessed by in vivo bioluminescence imaging. A significant 28% decrease in bilirubin production occurred within 3 h of SnMP treatment and persisted beyond 48 h. Bilirubin production decreased 15% and 9% by 3 h after administration of ZnBG and ZnPP, respectively, but returned to baseline within 48 h. Maximal inhibition of liver, spleen, and intestine HO activity was seen at 3 h with inhibitory effects decreasing in the order: SnMP > or = ZnBG > or = ZnPP. After SnMP treatment, HO-1 transcription increased 5.7-fold after 24 h. Furthermore, liver and spleen HO-1 protein significantly increased 3.7- and 2.0-fold, respectively, after 24 h. HO-1 transcription and protein were not affected in ZnBG- or ZnPP-treated mice. We conclude that the three Mps are absorbed at different rates in the mouse and affect bilirubin production and HO-1 expression in a tissue- and time-dependent manner.

K2M(H2P2O7)2·2H2O (M= Ni, Cu, Zn): orthorhombic forms and Raman spectra

The crystal structures of three isotypic orthorhombic dihydrogendiphosphates, namely dipotassium copper(II)/nickel(II)/zinc(II) bis(dihydrogendiphosphate) dihydrate, K2M(H2P2O7)2.2H2O (M = Cu, Ni and Zn), have been refined from single-crystal data. The M2+ and K+ cations are located at sites of m symmetry, and the P atoms occupy general positions. These compounds also exist in triclinic forms with very similar structural features. The structures of both forms are compared, as well as the geometry of the MO6 octahedron, which is considerably elongated towards the water molecules for M = Ni and Cu. Such elongation has not been observed among the other representatives of the family. A Raman study of the whole series K2M(H2P2O7)2.2H2O (M = Mn, Co, Ni, Cu, Zn and Mg) is reported.

A Novel Diamine Adduct of Zinc Bis(2-thenoyl-trifluoroacetonate) as a Promising Precursor for MOCVD of Zinc Oxide Films

A novel diamine (N,N,N',N'-tetramethyletilendiamine) adduct of zinc bis(2-thenoyl-trifluoroacetonate) has been synthesized in a single-step reaction. Single-crystal X-ray diffraction studies of Zn(tta)(2).tmeda provide evidence of a mononuclear structure with a six-coordinated zinc ion. The thermal behavior of this adduct points to mass-transport properties suitable for its application to MOCVD processes. This novel compound has been successfully applied as a precursor for the deposition of ZnO films on (100) Si and quartz substrates. The good quality of the deposited films indicates that the adduct is a very attractive precursor for MOCVD applications.

Molecular modeling study of the aggregation behavior of nickel(II), cobalt(II), lead(II) and zinc(II) bis(2-ethylhexyl) phosphate complexes

The physiochemical nature of the metal–extractant species in organic solvent has been a matter of debate over liquid–liquid extraction of transition metals by bis(2-ethylhexyl) phosphate. The aggregation behavior of nickel(II), cobalt(II), lead(II), and zinc(II) bis(2-ethylhexyl) phosphate have been investigated using molecular modeling. The recently confirmed “open” water channels rodlike reversed micelles which is in contact with the nonaqueous solvent rather than in an inner core (or “closed” water channel) of the nickel–extractant species by Ibrahim and Neuman appears to be a unique structure for such species. Lead–, cobalt– and zinc–extractant species behave in a different manner. The cobalt–extractant species form rodlike reversed micelles, but does not show the formation of any open water channel. The zinc– and lead–extractant species form ellipsoidal (or deformed spherical) reversed micelles with fewer water molecules located at the core of the micelles which is in accord with the conventional view of reversed micelles. The structural variations of the reversed micelles for the metal extracted species are in accord with the known extraction behavior of such metals when using HDEHP.