Ionic medium effects on equilibrium constants .1. Proton, copper(II), cadmium(II), lead(II) and acetate activity coefficients in aqueous solution

The molar single ion activity coefficients associated with hydrogen, copper(II), cadmium(II) and lead(II) ions were determined at 25 degrees C and ionic strengths between 0.100 and 3.00 M (NaClO4), whereas for acetate the ionic strengths were fixed between 0.300 and 2.00 M, held with the same inert electrolyte. The investigation was carried out potentiometrically by using proton-sensitive glass, copper, cadmium and lead ion-selective electrodes and a second-class Hg\Hg-2(CH3COO)(2) electrode. It was found that the activity coefficients of these ions (y(i)) can be assessed through the following empirical equations:log y(H) = -0.542I(0.5) + 0.451I; log y(Cu) = -1.249I(0.5) + 0.912I; log y(Cd) = -0.829I(0.5) + 0.448I(1.5);log y(Pb) = -0.404I(0.5) + 0.117I(2); and log y(Ac) = 0.0370I .

Separation of particles in time-dependent focusing billiards

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Methyl- and phenylmercury(II) derivatives of 2-mercaptobenzothiazole. Crystal structure of (2-mercaptobenzothiazolato)methylmercury(II)

The complexes MeHgL and PhHgL (HL = 2-mercaptobenzothiazole) have been obtained from the reaction of the ligand with methylmercury hydroxide and phenylmercury acetate, respectively, in methanol. MeHgL, which has been characterized by single-crystal X-ray diffraction analysis (crystal data: triclinic, space group P1, with a = 8.009 (4) Å, b = 10.042 (4) Å, c = 13.074 (3) Å, α = 101.25 (2)°, β = 102.61(3)°, γ = 101.42 (3)°, R = 0.067), crystallizes with two independent molecules, I and I′, contained in each asymmetric unit with a coordination geometry based on the almost linear C-Hg-S group (Hg-S = 2.369 (6) Å, Hg-C = 2.06 (2) Å, and C-Hg-S = 177.7 (7)° for I; Hg-S = 2.375 (6) Å, Hg-C = 2.10 (3) Å, and C-Hg-S = 178.8 (6)° for I′). A secondary intramolecular interaction between the mercury atom and the C=N group of the ring and some weak intermolecular interactions between the metal and sulfur atoms were also found. The vibrational spectra of this compound and the phenylmercury(II) compound are discussed in light of the crystal structure. Diagnostic criteria of the bonding modes for the ligand are assessed. © 1985 American Chemical Society.

Mercury(II) and thallium(III) organometallic derivatives of 2-Mercaptobenzoxazole

Some derivatives of 2-mercaptobenzoxazole (HL) of the type MRnL [M = Hg or Tl, R = Me or Ph and n = 1 (Hg) or 2 (Tl)] have been prepared. The structure of HgMeL has been determined by an X-ray diffraction study; in the crystal there are two independent planar molecules in each asymmetric unit, with the ligand in its thiolic form and an almost linear CHgS linkage. Weak intramolecular and intermolecular secondary interactions complement the mercurysulphur bond. The spectroscopic (IR, Raman, mass, 13C-NMR), conductimetric, and dipolar properties of this and the other compounds are discussed. © 1991.

Endothelial and neuronal nitric oxide synthase inhibitors influences angiotensin II pressor effect in central nervous system

The present study investigated the central role of angiotensin II and nitric oxide on arterial blood pressure (MAP) in rats. Losartan and PD123349 AT 1 and AT 2 (selective no peptides antagonists angiotensin receptors), as well as FK 409 (a nitric oxide donor), N W-nitro-L-arginine methyl ester (L-NAME) a constituve nitric oxide synthase inhibitor endothelial (eNOSI) and 7-nitroindazol (7NI) a specific neuronal nitric oxide synthase inhibitor (nNOSI) were used. Holtzman strain, (Rattus norvergicus) weighting 200-250 g were anesthetized with zoletil 50 mg kg -1 (tiletamine chloridrate 125 mg and zolazepan chloridrate 125 mg) into quadriceps muscle anda stainless steel cannula was stereotaxically implanted into their Lateral Ventricle (LV). Controls were injected with a 0.5 μl volume of 0.15 M NaCl. Angiotensin II injected into LV increased MAP (19±3 vs. control 3±1 mm Hg), which is potentiated by prior injection of L-NAME in the same site 26±2 mm Hg. 7NI injected prior to ANG II into LV also potentiated the pressor effect of ANG II but with a higher intensity than L-NAME 32±3 mm Hg. FK 409 inhibited the pressor effect of ANG II (6±1 mm Hg). Losartan injected into LV before ANG II influences the pressor effect of ANG II (8±1 mm Hg). The PD 123319 decreased the pressor effects of ANG II (16±1 mm Hg). Losartan injected simultaneously with FK 409 blocked the pressor effect of ANG II (3±1 mm Hg). L-NAME produced an increase in the pressor effect of ANG II, may be due to local vasoconstriction and all at once by neuronal NOS inhibition but the main effect is of the 7-NIT an specific nNOS inhibitor. The AT 1 antagonist receptors improve basal nitric oxide (NO) production and release. These data suggest the involvement of constitutive and neuronal NOS in the control of arterial blood pressure induced by ANG II centrally, evolving AT 1 receptor-mediated vasoconstriction and AT 2 receptor-mediated vasodilatation. These results were confirmed by the experiment using FK 409. © 2006 Asian Network for Scientific Information.

Adsorção de íons Cu(II) sobre superfícies de sílicas gel modificadas com 4-amino-2-mercaptopirimidina e com 2-mercaptopirimidina

Pós-graduação em Ciência dos Materiais - FEIS

Alterações histológicas do miocárdio, rim e fígado de ratos (Rattus novergicus) Wistar submetidos à infusão de angiotensina II: influência na função ventricular esquerda e resposta ao tratamento com losartan e carvedilol

Pós-graduação em Fisiopatologia em Clínica Médica - FMB

Estudo do comportamento térmico e eletroquímico do sistema 'PT 'RH' 15%- 'HG/CU'

Pós-graduação em Química - IQ

Multilayer adsorption of Cu(II) and Cd(II) over Brazilian Orchid Tree (Pata-de-vaca) and its adsorptive properties

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis and Physical-Chemical characterization of Metallic Nanoparticles

The stabilization of nanoparticles against their irreversible particle aggregation and oxidation reactions. is a requirement for further advancement in nanoparticle science and technology. For this reason the research aim on this topic focuses on the synthesis of various metal nanoparticles protected with monolayers containing different reactive head groups and functional tail groups. In this work cuprous bromide nanocrystals haave been synthetized with a diameter of about 20 nanometers according to a new sybthetic method adding dropwise ascorbic acid to a water solution of lithium bromide and cupric chloride under continuous stirring and nitrogen flux. Butane thiolate Cu protected nanoparticles have been synthetized according to three different syntesys methods. Their morphologies appear related to the physicochemical conditions during the synthesis and to the dispersing medium used to prepare the sample. Synthesis method II allows to obtain stable nanoparticles of 1-2 nm in size both isolated and forming clusters. Nanoparticle cluster formation was enhanced as water was used as dispersing medium probably due to the idrophobic nature of the butanethiolate layers coating the nanoparticle surface. Synthesis methods I and III lead to large unstable spherical nanoparticles with size ranging between 20 to 50 nm. These nanoparticles appeared in the TEM micrograph with the same morphology independently on the dispersing medium used in the sample preparation. The stability and dimensions of the copper nanoparticles appear inversely related. Using the same methods above described for the butanethiolate protected copper nanoparticles 4-methylbenzenethiol protected copper nanoparticles have been prepared. Diffractometric and spectroscopic data reveal that decomposition processes didn’t occur in both the 4-methylbenzenethiol copper protected nanoparticles precipitates from formic acid and from water in a period of time six month long. Se anticarcinogenic effects by multiple mechanisms have been extensively investigated and documented and Se is defined a genuine nutritional cancer-protecting element and a significant protective effect of Se against major forms of cancer. Furthermore phloroglucinol was found to possess cytoprotective effects against oxidative stress, thanks to reactive oxygen species (ROS) which are associated with cells and tissue damages and are the contributing factors for inflammation, aging, cancer, arteriosclerosis, hypertension and diabetes. The goal of our work has been to set up a new method to synthesize in mild conditions amorphous Se nanopaticles surface capped with phloroglucinol, which is used during synthesis as reducing agent to obtain stable Se nanoparticles in ethanol, performing the synergies offered by the specific anticarcinogenic properties of Se and the antioxiding ones of phloroalucinol. We have synthesized selenium nanoparticles protected by phenolic molecules chemically bonded to their surface. The phenol molecules coating the nanoparticles surfaces form low ordered arrays as can be seen from the wider shape of the absorptions in the FT-IR spectrum with respect to those appearing in that of crystalline phenol. On the other hand, metallic nanoparticles with unique optical properties, facile surface chemistry and appropriate size scale are generating much enthusiasm in nanomedicine. In fact Au nanoparticles has immense potential for both cancer diagnosis and therapy. Especially Au nanoparticles efficiently convert the strongly adsorbed light into localized heat, which can be exploited for the selective laser photothermal therapy of cancer. According to the about, metal nanoparticles-HA nanocrystals composites should have tremendous potential in novel methods for therapy of cancer. 11 mercaptoundecanoic surface protected Au4Ag1 nanoparticles adsorbed on nanometric apathyte crystals we have successfully prepared like an anticancer nanoparticles deliver system utilizing biomimetic hydroxyapatyte nanocrystals as deliver agents. Furthermore natural chrysotile, formed by densely packed bundles of multiwalled hollow nanotubes, is a mineral very suitable for nanowires preparation when their inner nanometer-sized cavity is filled with a proper material. Bundles of chrysotile nanotubes can then behave as host systems, where their large interchannel separation is actually expected to prevent the interaction between individual guest metallic nanoparticles and act as a confining barrier. Chrysotile nanotubes have been filled with molten metals such as Hg, Pb, Sn, semimetals, Bi, Te, Se, and with semiconductor materials such as InSb, CdSe, GaAs, and InP using both high-pressure techniques and metal-organic chemical vapor deposition. Under hydrothermal conditions chrysotile nanocrystals have been synthesized as a single phase and can be utilized as a very suitable for nanowires preparation filling their inner nanometer-sized cavity with metallic nanoparticles. In this research work we have synthesized and characterized Stoichiometric synthetic chrysotile nanotubes have been partially filled with bi and monometallic highly monodispersed nanoparticles with diameters ranging from 1,7 to 5,5 nm depending on the core composition (Au, Au4Ag1, Au1Ag4, Ag). In the case of 4 methylbenzenethiol protected silver nanoparticles, the filling was carried out by convection and capillarity effect at room temperature and pressure using a suitable organic solvent. We have obtained new interesting nanowires constituted of metallic nanoparticles filled in inorganic nanotubes with a inner cavity of 7 nm and an isolating wall with a thick ranging from 7 to 21 nm.

Spin-crossover in metallomesogens of iron(II)

Covalent grafting mesogenic groups to the coordination cores of the parent mononuclear low-spin and spin-crossover compounds afforded metallomesogenic complexes of iron(II). In comparison with the parent complexes the spin-crossover properties of the alkylated derivatives are substantially modified. The type of the modification was found to be dependent on the properties of the parent system and the nature of the used anion, however, the general tendency is the destabilization of the low-spin state at the favor of spin-crossover or high-spin behavior below 400 K. The structural insight revealed the micro-segregated layered organization. The effect of the alkylation of the parent compounds consists first of all in the change of the lattice to a two-dimensional lamellar one retaining significant intermolecular contacts only within the ionic bilayers. The comprehensive analysis of the structural and thermodynamic data in the homologous series pointed at the mechanism of the interplay between the structural modification on melting and the induced anomalous change of the magnetic properties. A family of one-dimensional spin-crossover polymers was synthesized and characterized using a series of spectroscopic methods, X-ray powder diffraction, magnetic susceptibility measurements and differential scanning calorimetry. The copper analogue of was also synthesized and its crystal structure solved. In comparison with the mononuclear systems, the polymeric mesogens of iron(II) are less sensitive to the glass transition, which was attributed to the moderate concomitant variation of the structure. Nevertheless, the observed increase of the magnetic hysteresis with lengthening of the alkyl substituents was ascribed to the interplay of the structural reorganization of the coordination core due to spin-crossover with the structural delay in the spatial reorganization of the mesogenic substituents. The classification of mononuclear and polymeric metallomesogens according to the interactions between the structural- and the spin-transition and analysis of the data on the reported spin-crossover metallomesogens led to the separation of three types, namely: Type i: systems with coupling between the electronic structure of the iron(II) ions and the mesomorphic behavior of the substance; Type ii: systems where both transitions coexist in the same temperature region but are not coupled due to competition with the dehydration or due to negligible structural transformation; Type iii: systems where both transitions occur in different temperature regions and therefore are uncoupled. Fine-tuning, in particular regarding the temperature at which the spin-transition occurs with hysteresis properties responsible for the memory effect, are still a major challenge towards practical implementation of spin-crossover materials. A possible answer to the problem could be materials in which the spin-crossover transition is coupled with another transition easily controllable by external stimuli. In the present thesis we have shown the viability of the approach realized in the mesogenic systems with coupled phase- and spin-transitions.

Untersuchung der Struktur und Assemblierung des Lichtsammelkomplexes II höherer Pflanzen mittels elektronenparamagnetischer Resonanz (EPR)

Der Haupt-Lichtsammelkomplex (LHCII) des Photosyntheseapparates höherer Pflanzen gehört zu den häufigsten Membranproteinen der Erde. Seine Kristallstruktur ist bekannt. Das Apoprotein kann rekombinant in Escherichia coli überexprimiert und somit molekularbiologisch vielfältig verändert werden. In Detergenzlösung besitzt das denaturierte Protein die erstaunliche Fähigkeit, sich spontan zu funktionalen Protein-Pigment-Komplexen zu organisieren, welche strukturell nahezu identisch sind mit nativem LHCII. Der Faltungsprozess findet in vitro im Zeitbereich von Sekunden bis Minuten statt und ist abhängig von der Bindung der Cofaktoren Chlorophyll a und b sowie verschiedenen Carotinoiden.rn Diese Eigenschaften machen LHCII besonders geeignet für Strukturuntersuchungen mittels der elektronenparamagnetischen Resonanz (EPR)-Spektrokopie. Diese setzt eine punktspezifische Spinmarkierung des LHCII voraus, die in dieser Arbeit zunächst optimiert wurde. Einschließlich der Beiträge Anderer stand eine breite Auswahl von über 40 spinmarkierten Mutanten des LHCII bereit, einen N-terminalen „Cys walk“ eingeschlossen. Weder der hierfür notwendige Austausch einzelner Aminosäuren noch die Anknüpfung des Spinmarkers beeinträchtigten die Funktion des LHCII. Zudem konnte ein Protokoll zur Präparation heterogen spinmarkierter LHCII-Trimere entwickelt werden, also von Trimeren, die jeweils nur ein Monomer mit einer Spinmarkierung enthalten.rn Spinmarkierte Proben des Detergenz-solubilisierten LHCII wurden unter Verwendung verschiedener EPR-Techniken strukturell analysiert. Als besonders aussagekräftig erwies sich die Messung der Wasserzugänglichkeit einzelner Aminosäurepositionen anhand der Electron Spin Echo Envelope Modulation (ESEEM). In Kombination mit der etablierten Double Electron-Electron Resonance (DEER)-Technik zur Detektion von Abständen zwischen zwei Spinmarkern wurde der membranständige Kernbereich des LHCII in Lösung eingehend untersucht und strukturell der Kristallstruktur für sehr ähnlich befunden. Die Vermessung kristallographisch nicht erfasster Bereiche nahe dem N-Terminus offenbarte die schon früher detektierte Strukturdynamik der Domäne in Abhängigkeit des Oligomerisierungsgrades. Der neue, noch zu vervollständigende Datensatz aus Abstandsverteilungen und ESEEM-Wasserzugänglichkeiten monomerer wie trimerer Proben sollte in naher Zukunft die sehr genaue Modellierung der N-terminalen Domäne des LHCII ermöglichen.rn In einem weiteren Abschnitt der Arbeit wurde die Faltung des LHCII-Apoproteins bei der LHCII-Assemblierung in vitro untersucht. Vorausgegangene fluoreszenzspektroskopi-sche Arbeiten hatten gezeigt, dass die Bindung von Chlorophyll a und b in aufeinanderfolgenden Schritten im Zeitbereich von weniger als einer Minute bzw. mehreren Minuten erfolgten. Sowohl die Wasserzugänglichkeit einzelner Aminosäurepositionen als auch Spin-Spin-Abstände änderten sich in ähnlichen Zeitbereichen. Die Daten deuten darauf hin, dass die Ausbildung der mittleren Transmembran-Helix mit der schnelleren Chlorophyll-a-Bindung einhergeht, während sich die Superhelix aus den beiden anderen Transmembranhelices erst im langsameren Schritt, zusammen mit der Chlorophyll-b-Bindung, ausbildet.rn

Continuous-Flow Magnetic Separation with Permanent Magnets for Water Treatment

More efficient water treatment technologies would decrease the water bodies’ pollution and the actual intake of water resource. The aim of this thesis is an in-depth analysis of the magnetic separation of pollutants from water by means of a continuous-flow magnetic filter subjected to a field gradient produced by permanent magnets. This technique has the potential to improve times and efficiencies of both urban wastewater treatment plants and drinking water treatment plants. It might also substitute industrial wastewater treatments. This technique combines a physico-chemical phase of adsorption and a magnetic phase of filtration, having the potential to bond magnetite with any conventional adsorbent powder. The removal of both Magnetic Activated Carbons (MACs) and zeolite-magnetite mix with the addition of a coagulant was investigated. Adsorption tests of different pollutants (surfactants, endocrine disruptors, Fe(III), Mn(II), Ca(II)) on these adsorbents were also performed achieving good results. The numerical results concerning the adsorbent removals well reproduced the experimental ones obtained from two different experimental setups. In real situations the treatable flow rates are up to 90 m3/h (2000 m3/d).

HLA class II mismatch alleles as targets of the alloreactive CD4 T-cell response

In allogeneic hematopoietic stem cell transplantation (allo-HSCT), alloreactive T lymphocytes of donor origin mediate the beneficial graft-versus-leukemia effect but also induce graft-versus-host disease (GvHD). Since human leukocyte antigens (HLA) mismatch alleles represent major targets of alloreactive T lymphocytes, patient and donor are usually matched for the class I molecules A, B, C, and for the class II molecules DRB1 and DQB1, in order do reduce the risk of GvHD. The HLA-DPB1 locus, however, is still ignored in donor selection. Interestingly, clinical studies have demonstrated that disparities at HLA-DQB1 alleles as well as distinct HLA DPB1 mismatch constellations do not adversely affect the outcome of allo-HSCT. It has also been shown that HLA class II is predominantly expressed on hematopoietic cells under non-inflammatory conditions. Therefore, this PhD thesis focused on the application of CD4 T cells in adoptive immunotherapy of leukemias.rnIn the first part of this thesis we developed a rapid screening approach to detect T-cell reactivity of donors to single HLA class II mismatch alleles. Allo-HLA reactivity was measured in naive, memory, and entire CD4 T cells isolated from PBMC of healthy donors by flow cytometric cell sorting according to expression of the differentiation markers CD45RA, CD45RO, CD62L, and CCR7. T-cell populations were defined by a single marker to facilitate translation into a clinical-grade allo-depletion procedure. Alloreactivity to single HLA-DR/-DQ mismatch alleles was analyzed in short-term mixed lymphocyte reactions (MLR) in vitro. As standard antigen-presenting cells, we used the HLA-deficient cell line K562 upon electroporation with single HLA-DR/-DQ allele mRNA. We observed in IFN-γ ELISpot assays that allo-HLA-reactivity preferentially derived from subsets enriched for naive compared to memory T cells in healthy donors, irrespective of the HLA mismatch allele. This separation was most efficient if CD62L (P=0.008) or CD45RA (P=0.011) were used as marker. Median numbers of allo-HLA-reactive effector cells were 3.5-fold and 16.6-fold lower in CD62Lneg and CD45RAneg memory CD4 T cells than in entire CD4 T cells, respectively. In allele-specific analysis, alloreactivity to single HLA-DR alleles clearly exceeded that to HLA-DQ alleles. In terms of alloproliferation no significant difference could be observed between individual CD4 T-cell subsets. rnThe second part of this thesis dealed with the generation of allo-HLA-DQ/-DP specific CD4 T cells. Naive CD45RApos CD4 T cells isolated from healthy donor PBMC by flow cytometric cell sorting were stimulated in MLR against single allo-HLA-DQ/-DP alleles transfected into autologous mature monocyte-derived dendritic cells by mRNA electroporation. Rapidly expanding HLA-DQ/-DP mismatch reactive T cells significantly recognized and cytolysed primary acute myeloid leukemia (AML) blasts, fibroblasts (FB) and keratinocytes (KC) in IFN-γ ELISpot and 51chromium release assays if the targets carried the HLA DQ/ DP allele used for T cell priming. While AML blasts were recognized independent of pre-incubating them with IFN-γ, recognition of FB and KC required IFN-γ pre treatment. We further investigated HLA class II expression on hematopoietic and non-hematopoietic cells by flow cytometry. HLA class II was not detected on primary FB, KC, and non-malignant kidney cells, but was expressed at significant levels on primary AML blasts and B-LCL. Up-regulation of HLA class II expression was observed on all cell types after pre-incubation with IFN-γ.rnIn summary, the novel K562-HLA based MLR approach revealed that naive-depleted CD4 T-cell subsets of healthy individuals contain decreased allo-HLA reactivity in vitro. We propose the application of CD45RAneg naive-depleted CD4 T cells as memory T cell therapy, which might be beneficial for HLA-mismatched patients at high-risk of GvHD and low-risk of leukemia relapse. Memory T cells might also provide important post-transplant immune functions against infectious agents. Additionally, the screening approach could be employed as test system to detect donors which have low risks for the emergence of GvHD after allo-HSCT. In the second part of this thesis we developed a protocol for the generation of allo-HLA-DQ/-DP specific CD4 T cell lines, which could be applied in situations in which patient and donor are matched in all HLA alleles but one HLA-DQ/-DP allele with low GvHD potential. These T cells showed lytic activity to leukemia cells while presumably sparing non-hematopoietic tissues under non-inflammatory conditions. Therefore, they might be advantageous for allo-HSCT patients with advanced stage AML after reduced-intensity conditioning and T-cell depletion for the replenishment of anti-leukemic reactivity if the risk for disease relapse is high. rn

Bio-inspired polymer-supported nitrido molybdenum(VI) complexes for ammonia synthesis − reactivity towards protons and electrons : EPR investigations on paramagnetic molybdenum(V) and copper(II) complexes

Die biologische Stickstofffixierung durch Molybdän-haltige Nitrogenasen sowie die Erforschung des zugrundeliegenden komplexen Mechanismus (N2-Aktivierung an Metall-Zentren, 6-fache Protonierung und Reduktion, N–N Bindungsspaltung unter Bildung von Ammoniak) ist von erheblichem Interesse. Insbesondere Molybdän-Komplexe wurden bereits erfolgreich als Modellverbindungen für die Untersuchung elementarer Einzelschritte der N2-Aktivierung eingesetzt. Durch die Verwendung von Triamidoamin-Liganden ist es Schrock et al. sogar gelungen mehrere Katalysezyklen zu durchlaufen und einen Mechanismus zu formulieren. Trotz der sterisch anspruchsvollen Substituenten in den Schrock-Komplexen ist die Umsatzrate dieses homogenen Katalysators, aufgrund Komplex-Deaktivierung infolge intermolekularer Reaktionen wie Dimerisierung und Disproportionierung, limitiert. In der vorliegenden Arbeit wurden einige dieser Herausforderungen angegangen und die aktiven Spezies auf einer Festphase immobilisiert, um intermolekulare Reaktionen durch räumliche Isolierung der Komplexe zu unterdrücken.rnEin Polymer-verankertes Analogon des Schrock Nitrido-Molybdän(VI)-Komplexes wurde auf einem neuen Reaktionsweg synthetisiert. Dieser beinhaltet nur einen einzigen Reaktionsschritt, um die funktionelle Gruppe „MoN“ einzuführen. Protonierung des immobilisierten Nitrido-Molybdän(VI)-Komplexes LMoVIN (L = Polymer-verankerter Triamidoamin-Ligand) mit 2,6-Lutidinium liefert den entsprechenden Imido-Molybdän(VI)-Komplex. Durch anschließende Ein-Elektronen-Reduktion mit Cobaltocen wird der Polymer-angebundene Imido-Molybdän(V)-Komplex erhalten, bewiesen durch EPR-Spektroskopie (g1,2,3 = 1.989, 1.929, 1.902). Durch die Immobilisierung und die effektive räumliche Separation der Reaktionszentren auf der Festphase werden bimolekulare Nebenreaktionen, die oft in homogenen Systemen auftreten, unterdrückt. Dies ermöglicht zum ersten Mal die Darstellung des Imido-Molybdän(V)-Intermediates des Schrock-Zyklus.rnEPR-Spektren des als Spin-Label eingeführten immobilisierten Nitrato-Kupfer(II)-Komplexes wurden unter verschiedenen Bedingungen (Lösungsmittel, Temperatur) aufgenommen, wobei sich eine starke Abhängigkeit zwischen der Zugänglichkeit und Reaktivität der immobilisierten Reaktionszentren und der Art des Lösungsmittels zeigte. Somit wurde die Reaktivität von LMoVIN gegenüber Protonen und Elektronen, welches zur Bildung von NH3 führt, unter Verwendung verschiedener Lösungsmittel untersucht und optimiert. Innerhalb des kugelförmigen Polymers verläuft die Protonierung und Reduktion von LMoVIN stufenweise. Aktive Zentren, die sich an der „äußeren Schale“ des Polymers befinden, sind gut zugänglich und reagieren schnell nach H+/e− Zugabe. Aktive Zentren im „Inneren des Polymers“ hingegen sind schlechter zugänglich und zeigen langsame diffusions-kontrollierte Reaktionen, wobei drei H+/e− Schritte gefolgt von einer Ligandenaustausch-Reaktion erforderlich sind, um NH3 freizusetzen: LMoVIN  LMoVNH  LMoIVNH2  LMoIIINH3 und anschließender Ligandenaustausch führt zur Freisetzung von NH3.rnIn einem weiteren Projekt wurde der Bis(ddpd)-Kupfer(II)-Komplex EPR-spektroskopisch in Hinblick auf Jahn−Teller-Verzerrung und -Dynamik untersucht. Dabei wurden die EPR-Spektren bei variabler Temperatur (70−293 K) aufgenommen. Im Festkörperspektrum bei T < 100 K erscheint der Kupfer(II)-Komplex als gestreckter Oktaeder, wohingegen das EPR-Spektrum bei höheren Temperaturen g-Werte aufzeigt, die einer pseudo-gestauchten oktaedrischen Kupfer(II)-Spezies zuzuordnen sind. Diese Tatsache wird einem intramolekularen dynamischen Jahn−Teller Phänomen zugeschrieben, welcher bei 100 K eingefroren wird.