Manganese Tricarbonyl Research Articles

Synthesis and transition metal complexes of 3,3-bis(1-vinylimidazol-2-yl)propionic acid, a new N,N,O ligand suitable for copolymerisation

The new N,N,O heteroscorpionate ligand 3,3-bis(1-vinylimidazol-2-yl)propionic acid (Hbvip) (5) was synthesised in five steps starting from 1-vinylimidazole. This ligand is closely related to 3,3-bis(1-methylimidazol-2-yl)propionic acid (Hbmip), but contains two vinyl linker groups which can be used for radical-induced polymerisation reactions. The κ3-N,N,O coordination behaviour of 5 was proven by the synthesis of the tricarbonyl complexes [Re(bvip)(CO)3] (6), [Mn(bvip)(CO)3] (7) and [Cu(bvip)2] (8). To obtain good yields of 6, it was synthesised in water instead of THF. The ligand as well as all three complexes were characterised by X-ray crystallography. Copolymerisation of 5 with pure methyl methacrylate (MMA) or a combination of MMA and ethylene glycol dimethacrylate (EGDMA) led to the solid phases P1 and P2. Polymer-bound rhenium and manganese tricarbonyl complexes could be obtained by the reaction of deprotonated P1 with [MBr(CO)5] (M=Re, Mn) and also by copolymerisation of 6 and 7 with MMA. In both cases, the facial tripodal binding behaviour was evidenced by IR spectra of the polymers. Furthermore, the content of metal incorporated in the polymers was determined by elemental analysis, AAS or ICP-OES measurements. Reaction of the deprotonated solid phase P1 with copper(II) chloride led to a blue solid-phase (P1-Cu). The UV–Vis absorption maximum of P1-Cu is found at 615nm, which is almost identical to that found for 8. Thereby, it seems likely that P1 is flexible enough to form bisligand complexes with copper(II). This means that the copper centres act as a kind of crosslinking agents. In contrast, the heterogeneous reaction of P2 with copper(II) chloride yielded a lime green solid phase (P2-Cu). The bathochromic shift of the absorption maximum by 102nm suggests one-sided bound copper centres.

Reduced Atmospheric Manganese in Montreal Following Removal of Methylcyclopentadienyl Manganese Tricarbonyl (MMT)

Methylcyclopentadienyl manganese tricarbonyl (MMT) was used between 1990 and 2003 as an antiknock agent and as an octane booster in Canadian unleaded gasoline. Its combustion leads to Mn emissions. The objective of this research was to examine the variations in atmospheric Mn in Montreal (Canada) from 2001 to 2007, covering the period prior (2001–2003) to and following (2005–2007) MMT use. Three sampling stations were selected because of their proximity to roads with widely differing and well-known traffic patterns. Filters from 2001 to 2007 were obtained from the Montreal Urban Community. The first sample of each month was selected, and Mn analysis was performed by neutron activation analysis. Total suspended particulates (TSP) was calculated by weighing the filters before and after dust collection. Results show a significant decrease of Mn over time at each station, whereas TSP decreased significantly in two stations. Comparing atmospheric Mn during and after the period of use of MMT 2001–2003 vs 2005–2007 showed a significant decrease at all stations. For TSP, only one station showed borderline significant decline between these two periods. Overall, between the two periods, Mn and TSP decreased by 39% and 17%, respectively. These data suggest that the combustion of MMT led to an increase of airborne Mn of approximately 22%. These findings should help in decision-making processes concerning the use of MMT in gasoline in other countries.

Ingestion of gasoline in a suicide attempt: an uncommon cause of bilateral basal ganglia T1 hyperintensities

A 70-year-old man with a 27-year history of psychosis and hypertension was brought comatose to our Emergency Room following a suicide attempt with oral unleaded gasoline ingestion that was witnessed and described by his neighbors. His neurological examination disclosed a Glasgow Coma Scale Score of 8 (eye opening response 2 points, verbal response 2 points, motor response 2 points), with normal brainstem reflexes and spontaneous breathing. The subject was treated with a gastric lavage (gastric content, almost 2 l of gasoline) and activated charcoal. A baseline brain CT was unremarkable, while his liver function tests were normal. His neurological status did not improve and was transferred to the Intensive Care Unit of our institution where severe aspiration pneumonia was diagnosed. A brain MRI was performed at 16 days following his suicide attempt. Bilateral hyperintensities affecting the globus pallidus and the caudate nucleus were shown on axial T1, T2 and FLAIR sequences (Fig. 1). The patient expired 3 weeks later because of his aspiration pneumonia. Lesions with high signal intensity on spin-echo Tl-weighted MR images are unusual and are associated with relatively few entities, including lipids, calcification, high protein count, laminar necrosis in cerebral infarction, neoplasms and paramagnetic substances such as methemoglobin, melanin, copper and manganese [1]. Manganese, in particular, is considered a neurotoxic agent causing movement and psychological disorders characterized by rigidity, tremor and hypokinesia in workers involved in the alloy industry (miners, welders, smelters), in patients receiving long-term total parenteral nutrition and in hepatic encephalopathy patients with portal liver shunts [1–3]. Since the introduction of MRI in clinical practice, bilateral symmetric high signal intensities at the globus pallidus and substantia nigra have been well described in patients with manganese neurotoxicity. The most plausible explanation for the increased T1 signal intensity is a rise in manganese concentration that has paramagnetic properties in the central nervous system (CNS), with preferential deposition in the globus pallidus. Methylcyclopentadienyl manganese tricarbonyl (MMT) is an octane-improving additive to unleaded gasoline, which has recently attracted attention with regard to the prospect of worldwide manganese exposure as increases in environmental manganese concentrations have been recorded relative to traffic density [4]. We postulate that in the present case oral ingestion of large quantities of gasoline resulted in MMT absorption, which in turn resulted in increased CNS manganese concentrations leading to bilateral T1 basal ganglia hyperintensities. However, it should be noted that manganese concentrations were not measured in blood, while we have no neuropathological confirmation of manganese deposition in globus pallidus. In conclusion, the present case highlights bilateral T1 basal ganglia hyperintensities related to oral ingestion of gasoline in a suicide case and underscores manganese neurotoxicity as the potential underlying cause of this uncommon neuroimaging presentation. G. Tsivgoulis (&) I. Heliopoulos K. Vadikolias C. Piperidou Department of Neurology, Democritus University of Thrace, University Hospital of Alexandroupolis, Kapodistriou 3, Nea Xili, 68100 Alexandroupolis, Greece e-mail: tsivgoulisgiorg@yahoo.gr

Manganese η2-Complexes as Auxiliaries for Stereoselective Aldol Synthesis of Allenyl Carbinols

A convenient and robust manganese auxiliary was linked via an η(2)-bond to alkynyl esters and ketones using a mild complexation reaction with methylcyclopentadienyl manganese tricarbonyl. This complex readily underwent aldol reactions with exclusive α-substitution and in good diastereoselectivities especially with aryl ketone substrates. This selectivity has been rationalized using a cyclic transition state model in which the manganese auxiliary plays a critical role in promoting E(O)-geometry of the cumulenolate intermediate.

Formation of a Manganese Tricarbonyl on the MgO Surface from Mn2(CO)10: Characterization by Infrared, Electron Paramagnetic Resonance, and X-ray Absorption Spectroscopies

The goal of this work was to prepare structurally well-defined manganese complexes on high-area MgO powder by vapor deposition of Mn2(CO)10. The supported species were characterized by infrared (IR), electron paramagnetic resonance (EPR), and X-ray absorption spectroscopies. The results show that when the manganese loading of the sample was 3.0 wt %, most of the Mn2(CO)10 was physisorbed, but when the loadings were less, chemisorbed species predominated, being formed by adsorption of Mn2(CO)10 on hydroxyl groups on the MgO surface. Treatment of samples containing 1.0 wt % Mn with O2 at room temperature resulted in oxidation of the manganese and the formation of surface species that are well represented as the d4 complex Mn(CO)3(Os)3 (where Os is surface oxygen of MgO), as indicated by IR and extended X-ray absorption fine structure (EXAFS) spectra. The EXAFS data show Mn−C, C≡O, and Mn−Os bond lengths as 1.90, 1.43, and 1.98 Å, respectively.

Analysis of Organometallic Gasoline Additives with the Composition-Explicit Distillation Curve Method

Problems associated with pre-ignition of fuel in a spark-ignition engine have been documented for many years and include poor performance and structural damage in engines. These problems were addressed in the past by adding organometallic additives, such as tetraethyl lead (TEL), to the fuel. While this additive is banned, others are permitted in some jurisdictions. Two such additives are ferrocene (FC) and methylcyclopentadienyl manganese tricarbonyl (MMT). In this paper, we apply the advanced distillation curve approach to the analysis of these two additives (at concentrations of 20 and 40 mg/L) in a typical gasoline. We observe that neither additive affects the volatility of gasoline until the 55% distillate volume fraction. Subsequent to this fraction, we note temperature departures from the base gasoline that progress from 1 to 7 °C for FC and from approximately 1 to 4 °C for MMT. We further note, with the composition-explicit data channel of the advanced distillation curve (ADC), that the additives are not found in the distillate until after the 55% distillate volume fraction and that the concentration in the distillate increases as the distillation proceeds to completion.

N,N,O Ligands Based on Triazoles and Transition Metal Complexes Thereof

AbstractThe reaction of 2H‐benzotriazole (1) with dichloroacetic acid leads to the symmetric bis(2H‐benzotriazol‐2‐yl)methane (2c) in 40 % yield. Deprotonation of 2c at the bridging methylene group and subsequent carboxylation with CO2 yielded the new tripodal N,N,O ligand bis(2H‐benzotriazol‐2‐yl)acetic acid Hbbta (3). The sterically less demanding sodium 3,3‐bis(1H‐1,2,4‐triazol‐1‐yl)propionate Na[btp] (5) was obtained by saponification of methyl 3,3‐bis(1H‐1,2,4‐triazol‐1‐yl)propionate (4). The heteroscorpionate ligand 3 was treated with [MnBr(CO)5] and [RuCl2(PPh3)3] to form the manganese tricarbonyl complex [Mn(bbta)(CO)3] (6) and the air stable ruthenium complex [Ru(bbta)Cl(PPh3)2] (7). DFT calculations and the IR spectra of the carbonyl complex 6 reveal ligand 3 to be a less electron‐donating ligand compared to the bis(1H‐pyrazol‐1‐yl)acetic acid Hbpza. In case of the 1H‐1,2,4‐triazole‐based ligand 5 formation of coordination polymers were observed as proven by the synthesis of [Zn(btp)2]∞ (8) and [Mn(btp)2]∞ (9). Polymer 8 crystallises in linear chains of zinc atoms bridged by two molecules of ligand 5 each. These polymer chains show an interesting π‐stacking interaction between uncoordinated triazole residues of the ligands. Deposition of the coordination polymer on highly ordered pyrolytic graphite (HOPG) was successful and was analysed by scanning tunnelling microscopy (STM). Reaction of Na[btp] (5) with MnSO4·H2O resulted in a metal organic framework (MOF) [Mn(btp)2]∞ (9).

Selective Additives for Improvement of Gasoline Octane Number

High octane blend base gasoline stocks are reformulated from 30% LSRN, 45% Reformate and 25% Powerformate on volume basis. ASTM standard and IROX 2000 analysis are performed to test blend stocks sample. Different additive types are used to improve octane number. These additives are tetraethyl lead, methylcyclopentadienyl manganese tricarbonyl; methyl alcohol, ethyl alcohol, iso-propanol, n-butanol, sec-butanol, tertiary butyl alcohol, tert-amyl alcohol, active amyl alcohol, iso-pentyl alcohol, isobutyl carbinol, benzol ,telone, xylene, amino benzene, N-N-dimethyl aniline, dimethyl ketone, and ethyl methyl ketone. Comparison is made between significant individual RON gains measured by standard CFR test-engine. The results indicated that the combined iso-propanol, oxinol (50/50 blend of methanol and TBA), aniline, and xylene with hydrocarbons fraction content in the gasoline base pool is better to ensure high RON. The results showed that a mixture of 20/54/10/16 of blend aniline/ iso-propanol/ oxinol/ xylene respectively, led to an increase in RON of gasoline blend pool from 84.5 to 96 RON, or 11.5% RON gain.

Bis(3,5‐dimethyl‐4‐vinylpyrazol‐1‐yl)acetic Acid: A New Heteroscorpionate Building Block for Copolymers that Mimic the 2‐His‐1‐carboxylate Facial Triad

AbstractThe new N,N,O ligand bis(3,5‐dimethyl‐4‐vinylpyrazol‐1‐yl)acetic acid (Hbdmvpza) (4) suitable for copolymerisation was synthesised in a multi‐step synthesis starting from bis(3,5‐dimethylpyrazol‐1‐yl)methane (1). The κ3‐N,N,O facial coordination behaviour of 4 was verified by synthesis and characterisation of the tricarbonyl compounds [Mn(bdmvpza)(CO)3] (5) and [Re(bdmvpza)(CO)3] (6), the ruthenium bisphosphane complex [Ru(bdmvpza)Cl(PPh3)2] (7), as well as the complex [Cu(bdmvpza)2] (8). Copolymerisation of 4 with methyl methacrylate (MMA) or ethylene glycol dimethacrylate (EGDMA) led to solid phases P1a, P1b and P2 with different amounts of incorporated ligand 4. Furthermore, a homopolymer H1 of ligand 4 was successfully synthesised. Copolymer‐bound manganese and rhenium tricarbonyl complexes P1a‐Mn, P1a‐Re, P2‐Mn and P2‐Re have been obtained by reaction of P1a and P2 with the metal precursors [MnBr(CO)5] and [ReBr(CO)5], respectively. The κ3‐N,N,O coordination of the manganese and rhenium centres was verified by IR spectroscopy and the amount of incorporated metal complex was determined by AAS or ICP‐AES measurements. Treatment of the deprotonated copolymer P1a or P2 with copper(II) or iron(II) led to polymers P1a‐Cu, P1a‐Fe and P2‐Fe. A bathochromic shift in the UV spectrum of P1a‐Cu compared to the absorption maximum of the homogeneous complex 8 by 64 nm indicates copper centres with one ligand moiety bound only. AAS analysis of P1a‐Fe and P2‐Fe show that up to 64 % of the ligand sites can be accessed withiron(II). Furthermore, two 2‐oxocarboxylato complexes [Ru(bdmvpza)(BF)(PPh3)] (9) (BF = benzoylformato) and [Ru(bdmvpza)(NOG)(PPh3)] (10) (NOG = N‐oxalylglycine) have been synthesised that mimic the shape of the active sites of 2‐oxoglutarate dependent iron oxygenases. The successful copolymerisation of 9 and 10 with EGDMA was proven by UV spectroscopy.

Selective Additives for Improvement of Gasoline Octane Number

High octane blend base gasoline stocks are reformulated from 30% LSRN, 45% Reformate and 25% Powerformate on volume basis. ASTM standard and IROX 2000 analysis are performed to test blend stocks sample. Different additive types are used to improve octane number. These additives are tetraethyl lead, methylcyclopentadienyl manganese tricarbonyl; methyl alcohol, ethyl alcohol, iso-propanol, n-butanol, sec-butanol, tertiary butyl alcohol, tert-amyl alcohol, active amyl alcohol, iso-pentyl alcohol, isobutyl carbinol, benzol ,telone, xylene, amino benzene, N-N-dimethyl aniline, dimethyl ketone, and ethyl methyl ketone. Comparison is made between significant individual RON gains measured by standard CFR test-engine. The results indicated that the combined iso-propanol, oxinol (50/50 blend of methanol and TBA), aniline, and xylene with hydrocarbons fraction content in the gasoline base pool is better to ensure high RON. The results showed that a mixture of 20/54/10/16 of blend aniline/ iso-propanol/ oxinol/ xylene respectively, led to an increase in RON of gasoline blend pool from 84.5 to 96 RON, or 11.5% RON gain.

Application of the Stabilization Method to Temporary Anion States of π-Ligand Transition-Metal Carbonyls in Density Functional Theory

In this paper, density functional theory is used to investigate (benzene)chromium tricarbonyl, (cyclopentadienyl)manganese tricarbonyl, (1,3-butadiene)iron tricarbonyl, and (cyclopentadienyl)cobalt dicarbonyl. For the energies of low-lying temporary anion states, the stabilized Koopmans-based (S-KB) and stabilized Koopmans theorem (S-KT) methods are adopted. Stabilization is accomplished by varying the exponents of appropriate diffuse functions. Results indicate that the calculations of S-KB using PBEPBE and S-KT using CAM-B3LYP are able to yield energies of temporary anion states in good agreement with the experimental values. Furthermore, the ionization potentials can be determined accurately via the Koopmans-based (KB) PBEPBE method.

Essentiality, Toxicity, and Uncertainty in the Risk Assessment of Manganese

Risk assessments of manganese by inhalation or oral routes of exposure typically acknowledge the duality of manganese as an essential element at low doses and a toxic metal at high doses. Previously, however, risk assessors were unable to describe manganese pharmacokinetics quantitatively across dose levels and routes of exposure, to account for mass balance, and to incorporate this information into a quantitative risk assessment. In addition, the prior risk assessment of inhaled manganese conducted by the U.S. Environmental Protection Agency (EPA) identified a number of specific factors that contributed to uncertainty in the risk assessment. In response to a petition regarding the use of a fuel additive containing manganese, methylcyclopentadienyl manganese tricarbonyl (MMT), the U.S. EPA developed a test rule under the U.S. Clean Air Act that required, among other things, the generation of pharmacokinetic information. This information was intended not only to aid in the design of health outcome studies, but also to help address uncertainties in the risk assessment of manganese. To date, the work conducted in response to the test rule has yielded substantial pharmacokinetic data. This information will enable the generation of physiologically based pharmacokinetic (PBPK) models capable of making quantitative predictions of tissue manganese concentrations following inhalation and oral exposure, across dose levels, and accounting for factors such as duration of exposure, different species of manganese, and changes of age, gender, and reproductive status. The work accomplished in response to the test rule, in combination with other scientific evidence, will enable future manganese risk assessments to consider tissue dosimetry more comprehensively than was previously possible.

Reduced Atmospheric Manganese in Montreal Following Removal of Methylcyclopentadienyl Manganese Tricarbonyl (MMT)

Reduced Atmospheric Manganese in Montreal Following Removal of Methylcyclopentadienyl Manganese Tricarbonyl (MMT)

Investigation of the Photochemical Behaviour of Tricarbonyl(cyclopentadienyl)manganese Derivatives with Carbamate Groups

AbstractPhotochemical properties of cymantrene carbamates were for the first time investigated. It was found that UV irradiation of Boc‐substituted 1‐aminoalkylcymantrenes yields dicarbonyl chelate complexes as a result of the coordination of the oxygen atom of the carbamate ligand to the manganese atom. These complexes show high thermodynamic and kinetic stability in solution at room temperature and in closed systems can be used for the creation of photochromic systems based on cymantrene carbamates.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Development of Ultrafast Photochromic Organometallics and Photoinduced Linkage Isomerization of Arene Chromium Carbonyl Derivatives

We review recent studies of processes relevant to photoinduced linkage isomerization of organometallic systems with the goal of preparing organometallics with an efficient and ultrafast photochromic response. The organometallic system thus corresponds to two linkage isomers with different electronic environments that are responsible for different optical properties. Much of this work has focused on examining processes following irradiation of cyclopentadienyl manganese tricarbonyl derivatives (compounds 3-21) including solvent coordination, thermal relaxation, solvent displacement by tethered functional groups (chelation), dissociation of tethered functional groups, and linkage isomerization. A new platform is investigated for obtaining a photochromic response in new experiments with arene chromium dicarbonyl complexes. A photochromic response is observed for arene chromium dicarbonyl complexes with tethered pyridine and olefin functional groups based on light-driven linkage isomerization on the nanosecond time scale. Irradiation at 532 nm of 23 ([Cr{eta(6)-C(6)H(5)CH(2-Py-kappaN)CH(2)CH=CH(2)}(CO)(2)]) (Py = pyridine) results in the isomerization to 22 ([Cr{eta(6)-C(6)H(5)CH(2-Py)CH(2)-eta(2)-CH=CH(2)}(CO)(2)]), and 355 nm irradiation isomerizes 22 to 23. The ultrafast linkage isomerization has been investigated at room temperature in n-heptane solution on the picosecond to microsecond time scale with UV- or visible-pump and IR-probe transient absorption spectroscopy by comparing the dynamics with model compounds containing only a tethered pyridine. Irradiation of 24 ([Cr{eta(6)-C(6)H(5)(CH(2))(3)(2-Py)}(CO)(3)]) and 25 ([Cr{eta(6)-C(6)H(5)(CH(2))(2)(2-Py)}(CO)(3)]) at 289 nm induces CO loss to immediately yield a Cr-heptane solvent coordinated intermediate of the unsaturated Cr fragment, which then converts to the kappaN(1)-pyridine chelate within 200 and 100 ns, respectively. Irradiation of 26 ([Cr{eta(6)-C(6)H(5)CH(2)(2-Py)}(CO)(3)]) also induces CO loss to immediately yield three species: the Cr-heptane solvent coordinated intermediate, a kappaN(1)-Py nitrogen chelate, and an agostic eta(2)-chelate in which the pyridine is coordinated to the metal center via a C-H agostic bond as opposed to the nitrogen lone pair. Both the transient Cr-heptane coordinated intermediate and the agostic pyridine chelate convert to the stable kappaN(1)-pyridine chelate within 50 ns. Similar reaction dynamics and transient species are observed for the chelate 33 ([Cr{eta(6)-C(6)H(5)CH(2)(2-Py)-kappaN}(CO)(2)]) where a Cr-Py bond, not a Cr-CO bond, initially cleaves.

A Chronic Iron-Deficient/High-Manganese Diet in Rodents Results in Increased Brain Oxidative Stress and Behavioral Deficits in the Morris Water Maze

Iron deficiency (ID) is especially common in pregnant women and may even persist following childbirth. This is of concern in light of reports demonstrating that ID may be sufficient to produce homeostatic dysregulation of other metals, including manganese (Mn). These results are particularly important considering the potential introduction of the Mn-containing gas additive, methyl cyclopentadienyl manganese tricarbonyl (MMT), in various countries around the world. In order to model this potentially vulnerable population, we fed female rats fed either control (35 mg Fe/kg chow; 10 mg Mn/kg chow) or low iron/high-manganese (IDMn; 3.5 mg Fe/kg chow; 100 mg Mn/kg chow) diet, and examined whether these changes had any long-term behavioral effects on the animals' spatial abilities, as tested by the Morris water maze (MWM). We also analyzed behavioral performance on auditory sensorimotor gating utilizing prepulse inhibition (PPI), which may be related to overall cognitive performance. Furthermore, brain and blood metal levels were assessed, as well as regional brain isoprostane production. We found that treated animals were slightly ID, with statistically significant increases in both iron (Fe) and Mn in the hippocampus, but statistically significantly less Fe in the cerebellum. Additionally, isoprostane levels, markers of oxidative stress, were increased in the brain stem of IDMn animals. Although treated animals were indistinguishable from controls in the PPI experiments, they performed less well than controls in the MWM. Taken together, our data suggest that vulnerable ID populations exposed to high levels of Mn may indeed be at risk of potentially dangerous alterations in brain metal levels which could also lead to behavioral deficits.

Patterned Monolayers of Neutral and Charged Functionalized Manganese Arene Complexes on a Highly Ordered Pyrolytic Graphite Surface

Complex patterns: The arene manganese tricarbonyl complexes [Mn(eta(5)-2,5-didodecoxy-1,4-semiquinone)(CO)(3)] and [Mn(eta(6)-1,4-dioctyloxybenzene)(CO)(3)] BF(4) form patterned monolayers on the surface of highly ordered pyrolytic graphite (HOPG), as a result of hydrogen-bonding, hydrophobic, and electrostatic interactions, leading to an ordered 2D array of manganese atoms or ions.

Manganese levels and chemical fractionation in street dust in South Africa

Mn in street dust and soil from selected roads was studied to assess the contribution of combustion of vehicular methylcyclopentadienyl manganese tricarbonyl (MMT) to Mn levels and distribution in Pretoria, South Africa. Total Mn concentrations ranged from (329.1-863.9 µg g -1 ) for dust and (215.8-450.6 µg g -1 ) for soil. These values were significantly higher than the mean value (278.9 µg g -1 ) found on soil from a rural environment in Pretoria. The lowest value for the dust sample (329.1 µg g -1 ) was close to the mean background level of 330 µg g -1 for Mn in soil. Mn distribution in the samples was most in the residual fraction (178.18-487.50 µg g -1 ) and (140.76-293.40 µg g -1 ) for dust and soil respectively. Mn in the other fractions were 56.45-202.60 µg g -1 oxides, 90.71-45.34 µg g -1 organic, 45.36-12.65 µg g -1 carbonates and 1.98-6.72 µg g -1 exchangeable for dust and 32.54-167.31 µg g -1 oxides, 34.23-70.45 µg g -1 organic, 10.98-30.45 µg g -1 carbonate and 1.0-4.87 µg g -1 exchangeable for soil. Major source of Mn

Metal-organic vapor phase epitaxy of crystallographically oriented MnP magnetic nanoclusters embedded in GaP(001)

Hybrid ferromagnetic-semiconductor GaP:MnP thin films were grown at 650 °C by metal-organic vapor phase epitaxy on GaP(001) using trimethylgallium, tertiarybutylphosphine, and methyl cyclopentadienyl manganese tricarbonyl (MCTMn). Overall Mn concentrations in the hybrid films, determined by Rutherford backscattering spectrometry, were found to be nearly proportional to the MCTMn precursor gas flow rate and ranged from 2 to 3.5 at. %. Cross-sectional transmission electron microscopy (TEM) analyses revealed the presence of a homogeneous distribution of 15–30 nm wide nanoclusters in a dislocation-free GaP matrix that is fully coherent with the substrate. The nanocluster facets are predominantly aligned along the (220) planes of the GaP matrix and selected-area electron diffraction patterns in TEM indicate that the nanoclusters are coherent (or semicoherent) with the single-crystal GaP matrix. The Mn:P composition ratio in the nanoclusters was determined to be 1.00±0.05 from parallel electron energy loss spectroscopy analyses. Increasing the MCTMn flow rate during film growth resulted in an increased concentration of MnP nanoclusters in the epilayer while their dimensions remained virtually unchanged. Magnetometric characterization indicates a ferromagnetic order, with a Curie temperature of about 294 K, originating from the MnP clusters.

Novel N,N,O Scorpionate Ligands and Transition Metal Complexes Thereof Suitable for Polymerisation

AbstractEsterification of 2,2‐bis(3,5‐dimethylpyrazol‐1‐yl)‐3‐hydroxypropionic acid (2) with methacryloyl chloride led to the new κ3‐N,N,O ligand 2,2‐bis(3,5‐dimethylpyrazol‐1‐yl)‐3‐methacrylato‐propionic acid (Hbdmpzmp) (3). The κ3‐N,N,O coordination as known from bis(3,5‐dimethylpyrazol‐1‐yl)acetic acid (Hbdmpza, 1) was proven by syntheses of the complexes [Mn(bdmpzmp)(CO)3] (4) and [Re(bdmpzmp)(CO)3] (5) and the single‐crystal X‐ray structure of 4. The methacrylic ester functionality makes 3, 4 and 5 suitable for polymerisation. Thus, copolymerisation of 3 with methyl methacrylate (MMA), a combination of MMA and ethylene glycol dimethacrylate (EGDMA) or pure EGDMA led to various solid phases (P1a–P1c, P2, P3a, P3b) with incorporated ligand. Polymer‐bound manganese and rhenium tricarbonyl complexes could be obtained by copolymerisation of 4 and 5 with MMA as well as by a polymer analogous reaction of P1a with appropriate metal salts. In both cases, the facial tripodal binding behaviour was evidenced by IR spectra of the polymer supported transition metal complexes and the uptake of manganese was proven by AAS measurements. Reaction of the soluble deprotonated solid phase P1a with copper(II) chloride led to a deep‐blue solid phase (P‐Cu‐I). The UV/Vis absorption maximum at 715 nm indicates the copper centres to act as crosslinking agent by a similar binding behaviour as in [Cu(bdmpza)2]. In contrast, the heterogeneous reaction of P1b with copper(II) chloride formed a lime‐green solid phase (P‐Cu‐II). The bathochromic shift of the absorption maximum by 78 nm suggests one‐sided bound copper centres. EPR spectra do not show exchange narrowing between the copper centres indicating the metal centres to be far enough apart from each other to prevent magnetic interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)