Editorial: 150 Years of the Technische Universität München: Innovation since 1868.

"… On Easter Sunday 1868, the decree founding the Polytechnische Hochschule München (today's Technische Universität München; TUM) was signed by the 23-year-old Ludwig II, King of Bavaria. Entrepreneurial spirit has been a hallmark of the TUM from the start, and it was the first German university to have a branch abroad. Interdisciplinary research is key, not least in the Department of Chemistry …" Read more in the Guest Editorial by Wolfgang A. Herrmann.

Direct Synthesis and Bonding Properties of the First µ(2)-η(2),η(2)-Allyl-Bridged Diiridium Complex.

The direct synthesis of the first µ(2)-η(2),η(2)-allyl-bridged diiridium complex ([2](+)), bearing the uncommon counterion [IrCl2(COD)](-) ([3](-)), is described. Both bridging moieties in [2](+), namely, allyl and acetate, are introduced in a single reaction step from [{IrCl(COD)}2] (1) and allyl acetate. A combination of X-ray crystallography and density functional theory calculations reveals pronounced metal-allyl π-back-bonding.

On the concept of hemilability: insights into a donor-functionalized iridium(I) NHC motif and its impact on reactivity.

Novel iridium(I) complexes bearing N-donor-functionalized N-heterocyclic carbene ligands were synthesized. Although hemilabile coordination of the attached donor is considered beneficial in catalysis, no detailed study of this phenomenon in these systems is available to date. The present report provides insight into the hemilabile bonding properties of a N,N'-bis(pyridin-2-yl)-imidazolylidene (NCN) ligand motif on iridium(I). In most cases, the presented compounds exhibit rare fluxional hemilabile coordination of the N donor, and remarkable performance in catalytic transfer hydrogenation is observed. Further, extensive reactivity studies often led to unexpected products.

Synthesis of the first radiolabeled 188Re N-heterocyclic carbene complex and initial studies on its potential use in radiopharmaceutical applications.

A novel approach towards the synthesis of radiolabeled organometallic rhenium complexes is presented. We successfully synthesized and analyzed the first (188)Re-labeled N-heterocyclic biscarbene complex, trans-dioxobis(1,1'-methylene-bis(3,3'-diisopropylimidazolium-2-ylidene))(188)rhenium(V) hexafluorophosphate ((188)Re-4) via transmetalation using an air-stable and moisture-stable silver(I) biscarbene complex. In order to assess the viability of this complex as a potential lead structure for in vivo applications, the stability of the (188)Re-NHC complex was tested in physiologically relevant media. Ultimately, our studies illustrate that the complex we synthesized dissociates rapidly and is therefore unsuitable for use in radiopharmaceuticals. However, it is clear that the transmetalation approach we have developed is a rapid, robust, and mild method for the synthesis of new (188)Re-labeled carbene complexes.

Group 7 transition metal complexes with N-heterocyclic carbenes.

This tutorial review summarizes all works and highlights recent advances published in the growing field of group 7 N-heterocyclic carbene (NHC) complexes. It provides a valuable source for all scientists that are interested in conducting research with new compounds bearing these metals. The article provides an overview of all manganese NHC complexes that are known to date. There are a lot of examples where manganese NHC complexes show unpredicted behaviour during synthesis, very different from other transition metal NHC complexes and their higher homologues rhenium and technetium. These differences are depicted and discussed. Furthermore, the chemistry of technetium NHC compounds and their chemical behaviour are discussed. To date published work on technetium NHC chemistry has been restricted to the oxidation state +v. It was found that such compounds are very reactive but show great stability in dry air. Their radioactivity makes such compounds interesting candidates for radiochemical applications. Since most group 7 NHC chemistry was conducted on rhenium NHC complexes, this tutorial review highlights the chemical behaviour of such compounds. Rhenium(i) complexes reveal luminescent properties, making them interesting candidates for applications ranging from biological markers to organic light-emitting diodes (OLEDs). Another interesting feature is the radioactivity of some compounds, which makes them excellent candidates for radiopharmaceutical research; hence their synthesis and reactivity are discussed.

[Effect of silymarin on liver health and quality of life. Results of a non-interventional study]. / Einfluss von Silymarin auf Lebergesundheit und Lebensqualität.

BACKGROUND: Many drugs are known to have hepatotoxic side effects. The effect of silymarin on liver function and liver-injury-impaired quality of life under daily practice conditions in patients with elevated values of liver enzymes was evaluated in the present non-interventional study. METHOD: Patients with drug-induced elevated aminotransferase levels and indication for silymarin (Legalon forte) treatment for 2 to 3 months were documented prospectively over 4 months. At baseline, after 2 and 4 months, respectively, the following parameters were documented: alanine transaminase (ALT), aspartate transaminase (AST), γ-glutamyltransferase (GGT), alkaline phosphatase, total bilirubin, presence of liver-related skin symptoms and discoloured urine, severity of liver-related symptoms and quality of life. RESULTS: In total, 190 patients (53.2% male, median age 60.0 years [range 19-81]) from 48 centres participated in the non-interventional study. Among potentially hepatotoxic drugs, analgesics/anti-inflammatory drugs were used most frequently (45.8%). These drugs have been administered for a median period of 2.8 years (range 0.0-26.1). At baseline, all patients had elevated levels of ALT, AST or GGT. Fatigue, flatulence, upper abdominal discomfort, lethargy, and joint complaints were the most severe liver-related symptoms and prevalent in over 62% of patients. Quality of life was affected in 88.7% of patients. Significant reductions were achieved in all documented laboratory parameters (p < 0.001), leading to marked improvement in liver-related symptoms and increased quality of life already after 2 months. The percentage of patients with liver enzymes in the normal range increased considerably within 4 months. No adverse drug reactions were observed. CONCLUSIONS: Silymarin is a safe and efficacious treatment option for patients with elevated liver enzymes. A benefit in terms of liver-related symptoms as well as quality of life and performance was demonstrated already after 2 months of treatment.

Exploring the scope of a novel ligand class: synthesis and catalytic examination of metal complexes with 'normal' 1,2,3-triazolylidene ligands.

Using new 'normal'-substituted 1,2,3-triazolylidene silver compounds as starting materials allowed for preparation of a series of molybdenum, ruthenium, rhodium, and palladium transition metal complexes bound to the new 1,2,3-triazolylidene ligand system. In this work, the first triazolylidene Mo compound is presented as well as the first structural investigation of a silver complex with a monodentate 1,2,3-triazolylidene. Furthermore, the triazolylidene Pd complex and the Mo complex were tested as precatalysts in Suzuki-Miyaura coupling and epoxidation catalysis, respectively.

Synthesis and comparison of transition metal complexes of abnormal and normal tetrazolylidenes: a neglected ligand species.

To date, only few examples of tetrazolylidene carbenes coordinated to transition metal complexes have been described. A direct comparison of "normal" tetrazolylidenes (1,4-substitution pattern) and "abnormal" tetrazolylidenes (also referred to as "mesoionic carbenes"; 1,3-substitution pattern) has not been performed at all. In this work, we describe coordination of both ligand types to a row of transition metals. For example, the first examples of tetrazolylidene Mo, Ag, or Ir complexes have been isolated and fully characterized. The mesoionic tetrazolylidene Ag compound 2d is shown to be a viable carbene transfer reagent. By means of NMR, IR, and Raman spectroscopy, as well as X-ray crystallography and computational results, the pronounced differences between the two ligand substitution patterns are highlighted. It is shown that simply changing the position of a methyl group from N3 to N4 in the heterocycle can cause enormous differences in ligand characteristics.

Synthesis and application of water-soluble NHC transition-metal complexes.

We provide an overview on the state-of-the-art in transition-metal complexes formed with water-soluble NHC ligands. Paths to introducing water solubility by ligand design are elucidated and some general properties of water-soluble NHC complexes are highlighted. The enhanced hydrophilicity of water-soluble catalysts offers advantages in applications. While studies based on C-C coupling reactions still dominate the field, recent reports show water-soluble NHC complexes can be applied in metathesis and hydrogenation reactions and turn out to be among the best performing catalysts known. Nevertheless, wide areas of this young field remain to be investigated, offering great potential for future research.

Hydrosilylation with biscarbene Rh(I) complexes: experimental evidence for a silylene-based mechanism.

A detailed study investigating the mechanism of the hydrosilylation of 4-F-acetophenone by N-heterocyclic biscarbene rhodium(I) complexes was performed, delivering substantial experimental evidence for a recently proposed catalytic cycle and explaining the observed side-product formation. Labeling experiments, silylene trapping reactions, and specific catalytic reactions were employed to substantiate each step of the catalytic cycle and explain the differences observed for different types of chiral catalysts. It is further shown that hydrosilylation and dehydrocoupling reactions with dihydrosilanes are mechanistically related.

Transformation of carbon dioxide with homogeneous transition-metal catalysts: a molecular solution to a global challenge?

A plethora of methods have been developed over the years so that carbon dioxide can be used as a reactant in organic synthesis. Given the abundance of this compound, its utilization in synthetic chemistry, particularly on an industrial scale, is still at a rather low level. In the last 35 years, considerable research has been performed to find catalytic routes to transform CO(2) into carboxylic acids, esters, lactones, and polymers in an economic way. This Review presents an overview of the available homogeneous catalytic routes that use carbon dioxide as a C(1) carbon source for the synthesis of industrial products as well as fine chemicals.

Mono- and bis- methyltrioxorhenium(VII) complexes with salen ligands: synthesis, properties, applications.

Methyltrioxorhenium(VII) (MTO) forms 1:1 (mono-) or/and 2:1 (bis-) complexes with salen ligands, undergoing a hydrogen transfer from a ligand-bound OH-group to a ligand nitrogen atom. Some complexes show good stability both in the solid state and in solution, while others must be kept at low temperatures under an argon atmosphere. X-ray crystallography shows distorted trigonal bipyramidal structures of all examined complexes in the solid state, this structure being due to the steric demands of the ligands, with the methyl group of MTO residing in the apical sites in the cis position. Temperature-dependent proton NMR data indicate that the coordination between salen ligands and MTO at low temperatures is considerably stronger than at room temperature. Density functional theory calculations have been performed to find approximate structures for all described complexes and to try to find a rationale for the preferred formation of mono- versus bis-MTO complexes. The formation of mono- or bis-MTO adducts is dependent on both the steric and the electronic influence of the respective salen ligands. The catalytic performance is strongly influenced by the ring substitution. Two MTO molecules coordinated to one salen ligand lead to an additional boost of catalytic activity because there is not only double the amount of catalytic centers present but also a "ligand enhanced" activity increase.

Epi-laser in situ keratomileusis: comparative evaluation of epithelial separation with 3 microkeratomes.

PURPOSE: To evaluate the cleavage plane, corneal cytoarchitecture, and cell vitality of separated corneal epithelial sheets created with 3 commonly used microkeratomes. SETTING: Laboratories of the Regensburg University Medical Center, Regensburg, Germany. METHODS: Mechanical separation of the epithelial layer in 10 porcine eyes and 2 human eyes was performed with 3 different microkeratomes (Amadeus II, Zyoptix XP, Epivision). Five of 10 porcine corneas and the 2 human corneas treated with each microkeratome were processed for histology, electron microscopy, and immunohistochemistry. In 5 of 10 porcine corneas, the corneal epithelial sheets were separated from the globe and cell vitality was assessed with the trypan blue dye vitality test. RESULTS: A reproducible epithelial separation with a smooth surface was achieved in all eyes. The cleavage plane was located between the lamina lucida and the lamina densa. Damage to epithelial cells was mainly limited to the cut margins. CONCLUSIONS: Mechanical separation of the epithelial sheet in epithelial laser in situ keratomileusis (epi-LASIK) was safe and reproducible with all evaluated microkeratomes. Immunohistochemistry and electron microscopy showed the cleavage plane in epi-LASIK was between the basal epithelium and the basement membrane at the level of the lamina lucida.

Macular hole surgery: an analysis of risk factors for the anatomical and functional outcomes with a special emphasis on the experience of the surgeon.

PURPOSE: The aim of this study was to evaluate risk factors for the anatomical and functional outcomes of macular hole (MH) surgery with special emphasis on the experience of the surgeon. METHODS: A total of 225 surgeries on idiopathic MHs (IMHs) performed by 6 surgeons with a mean follow-up period of 20.5 months were reviewed in this retrospective study. Outcome parameters focused on IMH closure, complications and visual acuity improvement. The results of MH surgeries performed by experienced surgeons were compared to those of surgeons in training. RESULTS: The average MH size was 381 µm (standard deviation [SD]=168). Brilliant blue G (BBG) for internal limiting membrane (ILM) staining was used in 109 (48%) eyes and indocyanine green (ICG) in 116 (52%) eyes. As endotamponade, 20% SF6 was used in 38 (17%) cases, 16% C2F6 in 33 (15%) cases and 16% C3F8 in 154 (68%) cases. IMH closure was achieved in 194 eyes (86%). Mean preoperative visual acuity was 0.84 logarithm of the minimum angle of resolution (log MAR; SD=0.29, range: 0.3-1.5); surgery led to a mean improvement of 0.40 (SD=0.37) log MAR. Although the MH closure rate was the same using BBG or ICG for ILM peeling, visual acuity improvement was better in eyes peeled with BBG compared to eyes peeled with ICG (log MAR: BBG: 0.38 [95% CI: 0.32, 0.44] vs ICG: 0.48 [95% CI: 0.42, 0.54], P=0.029). Surgeons with previous experience in vitreoretinal surgery of ≥6 years achieved better visual outcomes compared to surgeons with 0-3 years of experience, regardless of the MH size, preoperative visual acuity, time to follow-up or dye used for ILM peeling (0-3 years [0.27, Δlog MAR] vs ≥6 years [0.43, Δlog MAR], P=0.009). CONCLUSION: Our results indicate that vitrectomy with ILM peeling performed by non-experienced surgeons is a safe procedure leading to good anatomical and functional results. Very experienced surgeons may achieve even better functional outcomes.

Hydrogen Production and Storage on a Formic Acid/Bicarbonate Platform using Water-Soluble N-Heterocyclic Carbene Complexes of Late Transition Metals.

The synthesis and characterization of two water-soluble bis-N-heterocyclic carbene (NHC) complexes of rhodium and iridium is presented. Both compounds are active in H2 generation from formic acid and in hydrogenation of bicarbonate to formate. The rhodium derivative is most active in both reactions, reaching a TOF of 39 000 h-1 and a TON of 449 000 for H2 production. The catalytic hydrogenation reactions were carried out in an autoclave system and analyzed using the integrated peak areas in the 1 H NMR spectra. Decomposition of formic acid was investigated using a Fisher-Porter bottle equipped with a pressure transducer. Long-term stability for hydrogen evolution was tested by surveillance of the gas flow rate. The procedure does not require any additives like amines or inert gas conditions. Density functional theory calculations in agreement with experimental results suggest a bicarbonate reduction mechanism involving a second catalyst molecule, which provides an external hydride acting as reducing agent.

Olefin Epoxidation in Aqueous Phase Using Ionic-Liquid Catalysts.

Hydrophobic imidazolium-based ionic liquids (IL) act as catalysts for the epoxidation of unfunctionalized olefins in water using hydrogen peroxide as oxidant. Although the catalysts are insoluble in both the substrate and in water, surprisingly, they are very well soluble in aqueous H2 O2 solution, owing to perrhenate-H2 O2 interactions. Even more remarkably, the presence of the catalyst also boosts the solubility of substrate in water. This effect is crucially dependent on the cation design. Hence, the imidazolium perrhenates enable both the transfer of hydrophobic substrate into the aqueous phase, and serve as actual catalysts, which is unprecedented. At the end of the reaction and in absence of H2 O2 the IL catalyst forms a third phase next to the lipophilic product and water and can easily be recycled.

Synthesis of cyclic carbonates from epoxides and carbon dioxide by using organocatalysts.

The synthesis of cyclic carbonates through coupling of carbon dioxide with epoxides is 100 % atom economical and is already performed on an industrial scale. Its impact regarding the use of carbon dioxide as a renewable carbon source is expected to grow significantly in the near future, so that the development of efficient catalysts is of high interest in academia and industry. To improve the carbon footprint and sustainability of the cycloaddition reaction, the use of organocatalytic methods is a promising approach. Herein, available metal-free catalysts for the preparation of cyclic carbonates are described and elaborated concerning the overall sustainability of the process. Therefore, the required reaction conditions, as well as the activity of the catalysts and their reusability, are compared and evaluated. In addition to ammonium-, phosphonium-, or imidazolium-based single-component catalysts and their supported analogues, the growing field of research concerning dual catalysts are also discussed in detail.