Exchange programs

Project #1.

You will develop ways of producing next generation 3D polymer nanomaterials. These are based on polymer network scaffolds made by UV-crosslinking monomers inside a self-organising 3D nanomaterial template that we study here in Bath. As applications: the scaffolds can be functionalised with lithium ion or proton-conducting groups, where their structure allows 3D ion transport while maintaining mechanical strength, for high performance membranes in batteries, water hydrolysers or hydrogen fuel cells. In addition, we expect just the bare network to be optically transparent, super-hydrophobic, strong, and a fraction the weight of solid Perspex, plexiglass or other plastic window materials. As part of the project, you will learn how to make the materials, and how to characterise their structure and performance using small-angle X-ray scattering, rheology, electrochemical and NMR diffusion measurements, and mechanical testing.

Project #2.

Multi-metal nanoparticles often provide uniquely active catalysts for reactions such as production of hydrogen or hydrogen peroxide from ethanol or glucose. The ability to release hydrogen is equivalent to the release of energy and of potential use in energy technologies or in sensing. In this project, methods for making uniform and well-defined multi-metal nanoparticles ("high entropy alloy nanoparticles") will be tested and the resulting catalysts screened for performance. The project will provide skills in making catalytic materials, testing catalysts, characterisation with electron microscopy and diffraction techniques, and in using electrochemical techniques.

Project #3.

The long-standing interest in the medicinal chemistry of thiosemicarbazones (TSCs) for theranostic applications, multimodality imaging and cellular imaging assays has been largely driven by: a) the need to understand and tailor the cancer hypoxia selectivity in corresponding metal complexes, and b) the emergence of triapine as a cancer therapeutic. In this project we will adopt new by photochemical- and microwave-irradiation methodologies to synthesise a new family of TSC-based ligands characterized by flat and aromatic backbones.  The preparation of new ligands and of their zinc, copper, platinum, rhenium and ruthenium complexes, as precursors for future cancer metallodrugs, will proceed using our new rapid, efficient and straight-forward microwave-assisted method, which supersedes the conventional heating approaches. Furthermore, the bioconjugation with cancer targeting peptides, using new linkers chemistry and photochemistry-activatable tags, reliant on 'click' coupling chemistry in unconventional environments will be carried out. The probe design will render these entities intrinsically fluorescent and therefore traceable in living cancer cells. We will then 'shine light' onto the new thiosemicarbazonato metal complexes aiming to understand their speciation, through loss of ligand, in cells and we will image their cellular uptake and interactions using multiphoton confocal fluorescence imaging.  This approach will open up the field for simple and rapid bioconjugation protocols and lead to new opportunities for the design, discovery and delivery of new precision medicines for the imaging and treatment of cancers.

Project #4.

Various projects are available (which can be narrowed down at a later stage):

• Phosphonium Ylide Stabilised low oxidation state metal complexes
• New ligands for metal chemistry: N,N,N,N-, O,N,N,N- and O,N,N,O- ligands
• Metal-atranes complexes: new precursors for materials chemistry

Project #5.

Achieving a hydrogen-driven economy has become of great importance to replace fossil fuels. Electrolysis is one of the most promising methods to produce hydrogen via water splitting, where the hydrogen and oxygen evolution reactions (HER and OER, respectively) occur simultaneously. However, the OER is sluggish and leads to severe energy losses. We are studying Ir(O)_x(OH)_y catalysts for the oxygen evolution reaction and have shown that the presence of residual alkali metal salts from the preparation procedures can affect the morphology and composition of the catalyst surface and supress certain crystallisation processes which give rise to low activity catalysts. In this project you will develop skills in catalyst synthesis and in the electrochemical characterisation of new catalysts based on IrO_x and RuO_x in the presence of alkali metal salts. A wide range of techniques including electron microscopy, X-ray diffraction, and electrochemical tools will be employed, and the resulting catalysts will be compared to industry benchmarks. The effect of bulk and surface structure on the catalytic reaction will be investigated.

Project #6.

Polymers such as polylactic acid (PLA) made from sugar-derived molecules are crucial to achieving a circular economy. However, the production of lactide (a cyclic monomer containing two lactic acid molecules) currently has limitations that act as bottlenecks in PLA manufacture. Our group is working with iCAST (innovation Centre for Applied Sustainable Technologies) and industry partners to develop heterogeneous catalysts for the synthesis of lactide monomer from biomass sugars/cellulose. Some challenges in realizing this at scale include increasing the reaction rate, and improving selectivity towards the dimer while preventing oligomer formation through careful design/selection of the zeolite catalyst. The project will involve catalyst synthesis, testing, and characterization in order to develop an understanding of how catalyst structure affects performance.

Project #7.

Synthetic and physical chemistry of late transition metal complexes, particularly in connection with their use in small molecule activation and catalysis. This research encompasses elucidating the fundamental structure, bonding and reactivity of transition metal complexes, mechanistic investigations and subsequent catalyst development. There are mu;tiple proejcts on offer (which can be narrowed down at a later stage):

• Activation and transformation of alkanes, nitrous oxide, and nitric oxide.
• Supramolecular inspired encapsulating and interlocking ligand architectures
• Isolation and reaction chemistry of complexes with a low coordination number
• Organometallic chemistry of late transition metals in unusual oxidation states
• Applications of pincer ligands in organometallic chemistry and catalysis

Project #8.

The carbazole heterocycle describes a tricyclic alkaloid with two fused benzene rings towards a central pyrrole. This heterocyclic moiety forms the core of a number of natural as well as synthetic biologically active compounds. Furthermore, carbazoles have found application in materials science for application in electronic devices, such as OLED and solar cells. Hence, there is a steady interest in the development of strategies towards the synthesis and functionalisation of carbazoles. We propose a new synthetic strategy for an efficient, one-pot synthesis of carbazoles starting from commercially available reagents. We demonstrated previously that 2- haloanilines and fluoroarenes can be coupled in a one-pot procedure to give highly functionalised biaryls.1 This reaction sequence includes a fluorine-directed lithiation followed by transmetallation and palladium-catalysed Negishi cross-coupling (Scheme 1). These biaryls are suitable substrates for an intramolecular nucleophilic aromatic substitution. This synthetic strategy has been successfully applied to the synthesis of carbolines, benzofuropyridines and dibenzofurans, providing these tricyclic molecules in just four synthetic operations without the isolation of any intermediates. In this project, this synthetic synthetic strategy will be expanded to the synthesis of carbazoles. The reaction conditions for all steps will be optimised and the substrate scope for the transformation will be evaluated.

Project #9.

The Pike group studies the synthesis and catalytic properties of metal-oxo clusters. These clusters act as very small, high surface area particles of metal oxide and can retain similar properties. We are also able to study molecular metal-oxo clusters in solution with spectroscopic techniques to determine precise structure and reaction mechanism. This project will explore the use of Ce-oxo clusters (Fig 1) as Lewis-acidic catalysts for useful organic transformations. The student will explore the synthesis of cluster molecules, characterise their structure and explore reactivity and reaction mechanism with organic substrates.

Project #10.

Zeolites as microporous materials are of tremendous importance in the fields of catalysis, separation and sorption. Often their overall performance is limited by the mass-transfer processes occurring within their pore systems, which are often on length scales approaching 1 nm diameter. A more detailed understanding of such mass-transfer processes is thus a key aspect in improving the overall performance of zeolite materials for catalytic applications. In this regard infrared microimaging (IRM) is a useful tool to directly study the motion of molecules inside pores (in situ) and better understand the underlying diffusion phenomena which affect such transport processes. Due to technical limitations in the resolution of IRM, large crystal zeolites are typically needed to study more complex diffusion processes. In addition, introducing hierarchy within the pore system of the zeolite via a secondary pore system (e.g. micro-/mesoporous zeolites) is a facile approach to improve mass-transfer properties, coincidentally by mimicking naturally occurring hierarchical pore systems. It is thus the scope of this project to synthesize and characterize large crystal zeolites (mainly ZSM-5 and silicalite-1) for subsequent IRM studies of molecular diffusion. Furthermore, the introduction of an active phase (such as platinum) for catalytic studies in the future is in focus. The student joining this project will get insight into some of the following fields:

• zeolite synthesis (influence of synthesis parameters)
• introduction of a secondary pore system into zeolites by post synthesis modification (top-down approach)
• introduction of a catalytically active phase via different methods (impregnation, electrostatic adsorption)
• characterization of porous materials (nitrogen sorption, imaging techniques, elemental analysis, power X-ray diffraction)
• -uptake and diffusion measurements via IRM.
• This will allow the student to develop a broad background in materials synthesis, characterization, and potentially applied catalytic studies

Project #11.

Perovskites are possible electrode materials for solid electrolyte fuel and electrolysis cells. We are studying such materials (e.g. LaCoO₃, LaNiO₃ and others) in the context of solid oxide electrolysis cells (SOEC) for valorization of CO₂. Properties of such materials are studied by photoelectron spectroscopy methods. In particular, reactivity towards CO₂ will be studied. Goal is to investigate surface processes in presence of electric fields as they are expected in operating devices.

Project #12.

Reducing greenhouse gas emissions to combat climate change is one of the most pressing issues in science and society. Since a large part of the anthropogenic carbon dioxide emissions can be traced back to the use of fossil fuels, the search for alternative energy sources is of great importance. Hydrogen is very often discussed as a suitable substitute, especially since its chemical energy can be converted directly into electrical energy in fuel cells without greenhouse gas emissions using atmospheric oxygen. In addition, hydrogen can be produced via water electrolysis from regenerative power sources. However, transport and storage of hydrogen is not a trivial task as it can only be performed under high pressures and low temperatures. An alternative is the use of ammonia, which can be produced from hydrogen and atmospheric nitrogen in the Haber-Bosch process and converted back to hydrogen in an ammonia cracker. Therefore, in this project, a solid electrolyte-based fuel cell is to be produced, which is suitable for the conversion of hydrogen produced by ammonia cracking. To do this, the membrane electrode assembly (MEA) must be resistant to traces of ammonia in the hydrogen feed and oxygen corrosion. In addition, a high operating temperature is advantageous because the cell can be thermally coupled with an ammonia cracker to achieve optimal utilization of the thermal energy. Therefore, the fuel cell in this project is developed based on a solid electrolyte fuel cell, which can work at temperatures of over 240°C. The electrolyte membranes for the fuel cells based on the effect of a super protonic phase transition are to be produced in a hot-pressing process, characterized, and scaled up. The electrocatalyst is applied to CDP nanoparticles by a spray-drying process and this electrode-catalyst is transferred to the membranes. Characterization is carried out using REM, XRD, X-ray fluorescence, optical microscopy, and electrochemical measurements. In all steps, the process parameters are to be quantified and parameter studies are to be carried out to create an ideal manufacturing protocol. The finished cells are examined and characterized by in operando analysis methods such as thermometry and micro-X-ray computer tomography.

Project #13.

Adhesion GPCRs (aGPCRs) contain large ectodomains, including the unique GAIN domain characteristic of this receptor class. In humans, there are 33 aGPCRs classified into nine subfamilies. We are studying representatives of different species and subfamilies with the goal of resolving the structure of the ectodomains. This structural information is of great interest for elucidating receptor function and interaction. A unique feature of the aGPCR is the GAIN domain, which "catalyzes" autoproteolytic cleavage of the protein, leaving the cleavage fragments non-covalently associated.

The work will involve designing and preparing expression constructs at the DNA level. Subsequently, the expression of the constructs will be tested on a small scale. Successful test expression will be followed by large scale expression of the protein and its characterization. The specific aim of the current work is to characterize the autoproteolytic cleavage and dissociation of a specific agonist from the GAIN domain. Depending on the status of the project, some of the following working techniques will be used:

• Creation of expression constructs (primer design, cloning, plasmid preparation, potential optimization of constructs e.g. via mutagenesis)
• Protein expression (cell culture, HEK293 cells, transient/stable transfection, small-scale test expression, preparative expression in roller bottles)
• Purification and analysis (affinity chromatography, SEC, SDS-PAGE, Western blot, DLS, nanoDSF)
• Characterization of the influence of mutations on autoproteolysis and dissociation (mainly via gel analyses)

Project #14.

Some mixed-anionic compounds of the REPnCh (RE = rare-earth metal; Pn = P, As, Sb, Bi; Ch = S, Se, Te) family show charge density waves (CDW) at low temperatures. These compounds are characterized by layer-like structures that are variants of the PbFCl type. Tuning the composition by substitution while maintaining valence electron concentration may allow the manipulation of their physical properties.

For instance, PrSbS is promising in the field of structure manipulation by substitution, as its structure changes with temperature. In both cases the structure is built up from square atom layers,^[1] and the structural change involves symmetry reduction involving enlargement of the unit cell. Such structural changes have been linked to the appearance of CDW around the transition temperature, and they are not seen in comparable compounds of the same family (PrBiSe and PrBiTe). Thus, the possibility of manipulating the structural change in those compounds by substituting pnictogen atoms is open to investigation. After successful synthesis, the thermal and electrical transport properties can be characterized.

In this project, students are proposed to synthesize and characterize PrBi_xSb_1-xSe and PrBi_xSb_1-xTe with x ≤ 1. The elements will be mixed in stoichiometric ratios, pelletized under pressure, and heated to high temperatures under inert atmospheres (argon or vacuum). Repeating these steps should yield homogeneous samples. Samples will be analyzed using powder X-ray diffraction, including Rietveld refinements. The objective of this project is to conclude the feasibility of synthesizing PrBi_xSb_1-xSe and PrBi_xSb_1-xTe and the measurement of their physical properties.

Project #15.

The global spread of human pathogenic bacteria that are resistant to several, and in some cases all, clinically approved antibiotics has raised major concerns about rapidly increasing mortality and the prevalence of epidemic infectious diseases. In addition to various clinical measures to prevent the emergence and spread of resistant pathogens, there is general agreement that new classes of antibiotics are needed to treat multidrug-resistant pathogens. Antimicrobial peptides (AMPs) have been identified as a promising class of compounds that rely on different mechanisms to kill pathogens. Our research group is optimizing insect-derived proline-rich AMPs (PrAMPs) as novel antibiotics for the treatment of systemic infections in humans triggered by Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii and Pseudomonas aeruginosa, and the Gram-positive bacterium Staphylococcus aureus. The activities of several compounds have been confirmed in various murine infection models and we have elucidated the underlying mechanism of action.

The aim of the project is to synthesize new PrAMP analogs on solid phase, to purify them by RP-HPLC, to characterize them by mass spectrometry and to test their antibacterial activity against non-pathogenic bacteria.

Project #16.

The study of the coordination chemistry of lanthanide complexes with redox-active chelating ligands is a very topical research area. For example, an intensive search is being made for biomimetic complexes for the recently discovered lanthanide-dependent methanol dehydrogenases,¹ in order to understand the function of the rare earth elements in the catalytically active center and to develop new oxidation catalysts. Thus, our group is involved in the synthesis and characterisation of well-defined Ln³⁺ complexes bearing redox-active calix[4]arene ligands.² In the present project, diamagnetic La³⁺ and Yb³⁺ complexes will be synthesized and their electrochemical properties studied by cyclic voltammetry, EPR spectroscopy, and spectroelectrochemical methods.

Project #17.

A fundamental topic of the Tonner-Zech Group is the organic functionalization of semiconductor surfaces. This search was recently extended to Ge(001) surfaces building on the manifold investigation of the Si(001) surface. Various organic molecules have been investigated on the Si(001) surface and now on Ge(001). The reactions and structures have been characterized from a theoretical perspective. One of the most interesting results in the last years is the ring-opening reaction of THF on both surfaces which is observed as an SN2-type reaction. Trends that can be expected from the HSAB have been observed for the different surfaces. One remaining research question from the observed trends is the effect of the substitution of the reactive species in molecules and how the surface reactivity will be affected. This project has the goal of extending the research of tetrahydrofuran to the sulfur-analog tetrahydrothiophene to gain insight into the effects of polarizability and electronegativity on the structures and the reactivity.

Project goals:

* Study of adsorption structures of THT on Ge(001) using DFT theory

* Investigation of the reaction kinetics using NEB methods.

* Characterization of the adsorption structures and transition states utilizing bonding analysis (pEDA)

Possible Extensions to the project:

* Investigation of THT on Si(001)

* Simulation of adsorption dynamics utilizing AIMD

* Charge analysis using different partial charge schemes

Project #18.

We have recently investigated cycloadditions of transient ortho-quinone methides in great detail which give rise to a plethora of enantiomerically highly enriched benzannulated oxygen and nitrogen heterocycles.[1] Moreover, we have been able to extend this methodology to transient indole-2- and pyrrole-2-methides.[2]

It is the goal of this project to develop a novel synthesis of pyrrolo[1,2-a]indoles upon reaction of pyrrole-2-carbinols and enolrich aldehydes under chiral Brønsted acid catalysis. We envision a facile dehydration of the carbinol upon addition of the chiral phosphoric acid to produce a transient and hydrogen-bonded indole-2-methide. This in turn will hydrogen-bond to the enol tautomer of the aldehyde as well and undergo a (3+2)-cycloaddition in a highly organized transition state such as the one depicted to produce highly valuable pyrrolo[1,2-a] indoles in a single step from commercially or readily available substrates.

This methodology has been investigated in the context of ortho-quinone methide chemistry and is likely to be adopted to indole chemistry as well.

Project #19.

For more information see: https://www.tu.berlin/en/funktionsmaterialien

Project #20.

For more information see: https://www.biologie.hu-berlin.de/en/groupsites/struktbio/projekte-en

Project #21.

For more information see: https://www.unicat.tu-berlin.de/driess/

Project #22.

Two potential projects are available.

The first project is in sustainable synthesis. The development of novel catalytic reaction, in which alcohols are converted into important classes of compounds, contributes to the saving of our fossil carbon resources and the lowering of CO2 emission since alcohols can be obtained from indigestible and abundantly available biomass such as lignocellulose. The aims of this project are the rational design of such reactions and of catalysts mediating them.

The second project is in earth abundant transition metal catalysis. The conservation of our element resources is of outmost importance with regard of the future of mankind. One approach to save rare elements is their replacement by abundantly available elements in key technologies. Catalysis is a key technology and often mediated by rare noble metals. We are interested in replacing noble metals such as Pt, Pd, Ir, Rh or Ru by so called base metals (Co, Fe and Mn) in catalysis. Homogenous catalysis is used to explore the scope of such a replacement and to develop novel catalytic reactions mediated by base metals.

Project #23.

Polymer derived silicon carbon (nitride) [SiC(N)] ceramics exhibit interesting catalysis relevant properties such as high thermal stability, great resistance against chemicals and structuring at multiple lengths scales. When modified with metals, such a material could be employed as a heterogeneous catalyst. The aim of the project is the development of the catalyst class and applications of the catalysts in sustainable synthesis and energy storage.

Project #24.

We have a strong interest in the controlled and efficient polymerization of ethylene and novel products accessible by such controlled polymerization processes. In addition, we are interested in novel on-demand olefin syntheses.

Project #25.

Polymers play an esseherlandsntial role in everyday life and new functional polymer materials are of increasing importance in a wide range of applications, not least in creating smart surfaces and organic electronics. Making durable functional surfaces means that chemically robust and versatile building blocks are used. A prominent monomer used in many systems is the carbazole motif, which has proven to be highly versatile in providing efficient (electro)dimerization/polymerization. The polymerizability of carbazole derivatives is highly sensitive to their precise structure and especially steric constraints, but, surprisingly carbazole carbazole coupling remains a poorly understood process.

The key challenge in understanding oxidative di- or polymerization lies in characterization of the polymers formed at the ‘molecular’ level. Self-assembled monolayers (SAM’s), however, can help us shed light on these systems by providing us with a means to identify a single coupling event in real time.

In this research project, you will synthesis a novel surface-anchorable carbazole, containing a disulfide for attachment to a gold substrate. Once synthesized and characterized by elemental analysis, mass spectrometry and vibrational and NMR spectroscopy, the compound will be self-assembled on a roughened gold surface for analysis by Surface Enhanced Raman Spectroscopy (SERS) before, during and after electrochemical oxidation to form carbazole dimers on the surface.

If time permits, mixed monolayers may be made with a highly concentrated co-adsorbate, which does not undergo oxidative dimerization, and the electrochemical behavior of isolated carbazoles will be elucidated. A key experiment will be to couple the surface bound carbazole to carbazole units in solution.

In this project you will develop skills in the synthesis and purification of organic compounds by standard synthetic methods and their characterization with spectroscopic methods. You will gain experience with self-assembled monolayers and their characterization by surface enhanced Raman spectroscopy and spectroelectrochemistry.

Project #26.

Parity violation (PV) through the weak interaction is a well-established phenomenon is nuclear and atomic physics. In chiral molecules, the weak neutral current between the electrons and the nucleus is predicted to result in a tiny energy difference between the two enantiomers. Due to this energy difference, the lower-energy enantiomer would be present in slight excess in an equilibrium mixture; this imbalance may provide a clue to the origin of biomolecular homochirality, i.e. why chiral molecules often occur in only one enantiomeric form in nature. However, to date, PV has not been detected in molecules, and the experimental search continues. As the observable effects are expected to be extremely small, the success of such measurements strongly depends on the choice of the molecule.

The topic of the proposed research project is theoretical investigation of the sensitivity of different chiral molecules to parity violation. The calculations will be carried out using the relativistic density functional theory (DFT). The most promising molecular transition for guidance of future measurements will be identified.

Project #27.

Even before the Nobel Prize in 2021, asymmetric organocatalysis attracted much attention in organic synthesis. An example is the well-established benzoin addition. The benzoin addition consists of two steps, the first step is the umpolung of an aldehyde, and the second is the nucleophilic attack of the aldehyde to a carbonyl carbon. The aim of the project is to test an intramolecular ring-closing benzoin addition forming two stereocenters, with both achiral and chiral organocatalysts on a previously reported substrate. In this project the student will first synthesize N-heterocyclic carbenes (NHC) and the required reaction substrate. Finally, the prepared catalysts will be tested in the target reaction.

The goal of the project is to get further insights in the intramolecular ring-closing benzoin additions reaction for further optimization of the reaction conditions. Within the Pollice research group, there is also an interest in the automatization of lab workflows. During this project, the student can, if advantageous, use the Opentron-2 liquid dispensing robot to increase the reaction throughput.

Screening of substrate scope: First, the student works on the substrate scope. This can be done by changing two different things: on the one hand, the ring size can be changed, on the other hand, the R1-group, which eventually is bound to the second chiral centre, can be changed.

Screening of amino acids: The amino acid sequences attached to the NHC will be changed.

Screening of alkylating groups: The organocatalyst can also be changed on both N-positions of the carbene. The effect of different amino acids, different peptide-sidechain length, or the effect of different R2-group on the reaction yield and the enatiomeric excess (e.e.) can be studied.

Reaction condition screening: The effect of reaction conditions on the yield and the e.e. could also be studied. Herein, varying the temperature or the base might prove effective.

Project #28.

Since the 60’, micro- and nanoparticles (M&NPs) have had a powerful impact in biomedical applications such as imaging, diagnosis, and drug delivery. Since then, various classes of spherical M&NPs have been designed, mainly by tuning compositions, sizes, and surface properties. More recently, a new criterion to control biological processes has been added by conceiving M&NPs with specific shapes. Synthetic nonspherical M&NPs have been generated using different fabrication techniques divided into bottom-up and top-down approaches. However, all those techniques are batch processes that have several drawbacks: (i) they result in large particles (typically >150 nm), (ii) high polydispersity, and (iii) high batch-to-batch variation. Those drawbacks are sub-optimal for biological applications. To address current challenges in M&NPs formulation, microfluidic technologies have been used to prepare NMs with more controlled physicochemical properties and good reproducibility. Interestingly the size can be varied from 20 nm to 80 nm by acting on microfluidic device geometry and the process parameters. Work Packages (WP) in the project will include:

WP1: M&NPs used in this proposal are composed of biodegradable poly(lactic acid) stereocomplexes. Those materials provide unique properties, such as the control of the molecular architecture. The molecular weight and the stereoregularity will be tuned. For the biological evaluations, a fluorescent dye^[4] will be covalently grafted on the polymer backbone.

WP2: Once synthesized and characterized, the polymers will be used to formulate the M&NPs. Spherical M&NPs will be prepared by nanoprecipitation in a microfluidic device. Nonspherical M&NPs will be designed by adapting protocols previously reported in the literature.

WP3: NM dimensions, concentration, morphology, volume, surface specific areas, mechanical properties, the surface potential will be assessed using conventional physicochemical and physical methods of characterizations