Chair of Inorganic and Analytical Chemistry
The N,N,O binding motif is the key aspect of our research. This motif is found in many non-heme iron enzymes as well as in some zinc enzymes, for example the gluzincins, as metal binding motif. Thus, to mimic this motif is the purpose of most of our model complexes for these iron and zinc enzymes. Small organic k3-N,N,O ligands such as various bis(pyrazol-1-yl)acetato ligands are applied for this purpose. These ligands can be tailored with bulky substituents to modify their steric hindrance and with solid phase linkers for solid phase fixation. Some of these anionic k3-N,N,O ligands, we developed, are also quite useful in organometallics and coordination chemistry and allow a chemistry comparable to that of cyclopentadienyl (Cp) or hydrido(trispyrazol-1-yl)borato ligands (Tp). This includes future potential applications in radiopharmaceuticals.
Furthermore, new chiral enantiopure N,N,O tripod ligands have been developed starting from cheap compounds of the Chiral Pool. Finally, we try to investigate the biocatalytic pathways of the non-heme iron dioxygenases by pseudo kinetic protein crystallography.
Chair of Organic Chemistry I
Focus of current research interests lies in the area of modern supramolecular chemistry. Weak supramolecular interactions are used to recognize and specifically bind small guest molecules by specifically designed host molecules (keywords: anion recognition, sensors). Such recognition processes are further exploited in chemical catalysis. Thereby, the main interest lies on transformations using aqueous solution as reaction media.
Chair of Organic Chemistry II
Our research is devoted to the design of new materials composed of various molecular building blocks such as fullerenes, carbon nanotubes, porphyrines, dendrimers, calixarenes and acetylene compounds. These functional units are linked by covalent bonds or via supramolecular organization. The aim is to generate structures, which, for example, represent models for redox proteins, enable a directed photo-induced electron- or energy transfer, can form micellar containers for the encapsulation of guest molecules, are useful for applications in the field of molecular electronics and serve as new redox active drugs. The basis for the successful realization of such complex architectures is a) the development of new synthesis concepts, for example, for chiral and amphiphilic building blocks as well as for derivatives of carbon rich molecules, b) the systematic investigation of the self-assembly of achiral and chiral supramolecular organization motifs and c) the calculation of molecular properties with quantum mechanical methods.
- Water-soluble highly charged metalloporphyrins
- Novel porphyrin systems for the Photodynamic therapy of tumors
- Crown ether-appended metalloporphyrins
Chair of Physical Chemistry I
This outline summarizes our current research activities, namely, the application of an arsenal of spectroscopic and microscopic techniques to a variety of molecular systems designed specifically to explore the nature of the chemical, physical and photophysical properties of new molecular architectures. In particular, we explore new preparative strategies towards supramolecular hybrids, quantum dots, quantum rods and nanoparticles. Our experimental tools span from ultrafast spectroscopy (absorption and fluorescence) and vibrational spectroscopy (Raman and IR) to electrochemistry and microscopy (Raman, TEM and AFM). Such conception is extremely valuable for the realization of solar energy conversion, photovoltaics, and catalytic reactivity, specifically to novel chemical and light driven systems.
The first research project (I) is targeted to the elucidation of the dynamic interactions between carminic acid and DNA in aqueous buffer solution at pH=7 (BPES), whereas the focus of the second research project (II) is directed to the application of fluorescence spectroscopy to the study of the transport properties of P-glycoprotein in Caco-2 cells.
I. The excitation relaxation dynamics of carminic acid-DNA complexes are examined using femtosecond resolved transient absorption spectroscopy and fluorescence upconversion. The evaluation of the transient absorption spectroscopic data of carminic-acid in BPES yields four lifetimes for the excited state (S1): 8 ps, 15 ps, 33 ps and 46 ps. The four S1 lifetimes are ascribed to the coexistence of the normal and tautomer form of carminic acid in its non dissociated state (i.e. CAH and CAHT) and in its deprotonated state (i.e. CA- and CA-T), respectively. The two lifetimes of CA- T and CAHT, 33 ps and 46 ps, are confirmed by fluorescence up-conversion spectroscopy. The formation of intercalation complexes between carminic acid and DNA is associated with a prolongation of the two lifetimes which is explained by the rigid environment of the base pairs stacking.
II. For the pharmacokinetic study of P-glycoprotein the fluorescence dye rhodamine-123 is used as substrate. While the apical-to-basolateral transport of the dye occurs through pores of the Caco-2 cell membrane, P-glycoprotein mediates the basolateral-to-apical transport.
Chair of Physical Chemistry II
The research activities of the Steinrück group focus on the area of surface and interface science with the main research interests in:
- New materials with novel electronic, geometric and chemical properties (metals, alloys, oxides, semiconductors, organic layers, ionic liquids; ultrathin layers and lateral nanostructures; growth modification and electronic, geometric and chemical properties).
- Elementary steps of surface reactions (various model reactions on structured surfaces with particular emphasis on the influence of the surface structure on reactivity and reaction pathways; fundamental physical and chemical understanding of the mechanisms and processes involved).
- Development and construction of scientific apparatus (photoelectron spectrometer for in-situ XPS at synchrotron radiation sources; “high-pressure XPS” setup for measurements up to 1 mbar). The applied experimental methods include electron spectroscopy (XPS, UPS, AES, NEXAFS), scanning electron, scanning Auger and scanning tunneling microscopy (SEM, SAM, STM), electron diffraction (LEED), low energy ion scattering (LEIS), temperature programmed desorption (TPD) and molecular beam methods. Measurements at synchrotron radiation facilities are performed since 1986, mainly at BESSY, but also at MAX-II, ELETTRA, ALS and ESRF).
Large organic molecules have become promising materials in molecule based electronics (field effect transistors, light-emitting devices) due to the possibility to tailor their electronic and optical properties. However, the properties of the electronic devices largely depend on the structural properties of the organic film. In case of sufficiently large interactions at the interface between the organic molecules and the underlying substrate (usually metal single crystals) the geometric properties of the film can be controlled.
We concentrate on the electronic and structural properties of the metal-organic hybrid systems using high-brilliance synchrotron radiation. In order to monitor lateral inhomogeneities on a lateral length scale below 30 nm, we are developing high-resolution microspectroscopes utilizing the superior spectral contrast in the near-edge x-ray absorption spectra of organic molecules. Further interests concern magnetic studies, ferrofluids and microscopic studies of biological objects.
- Surface Coordination Chemistry
- Model Catalysis
- Surface Nanocalorimetry
- Ionic Liquids
Chair of Theoretical Chemistry
Quantum chemistry in general and density-functional methods in particular have gained more and more importance in chemistry over the last decades. Today research in chemistry is often driven by a close interplay between experiment and theory. Our group develops and applies new density-functional methods both for finite systems, i.e., molecules or clusters, and for periodic systems, i.e., polymeres, molecular wires, surfaces, or solids. Ground and excited electronic states as well as response properties, like NMR parameters or like hyper-polarizabilities for the characterization of nonlinear optical properties are considered.
Computer Chemistry Center (CCC)
The research group develops and applies calculation techniques for investigating the mechanisms of chemical and biological processes. Our main interests lie in the mechanisms of reactions of ligands coordinated to redox-active metal centers, reactions of organic radicals and conformational changes in proteins that lead to biological signal transduction.