Aarhus University Seal / Aarhus Universitets segl

Kemifaglige foredrag 2013

14.11.2013 Prof. Andrew Beeby

Andrew Beeby

Luminescent materials are widely employed in today's technological world and can be found in the most unexpected places - for example pet budgerigars fluoresce nicely!  Luminescence helps to protect our precious goods and money, it is used are used as a tracer or probes in medical diagnostics and the next generation of TV screens will contain light emitting materials.  Fundamental to harnessing the brilliant world of luminescence is a thorough understanding of molecular excited states and how these are influenced by molecular structure.  The presentation will provide a glowing report, showing a range of applications of luminescence and optical spectroscopy.  It will end with an example of an unlikely but rewarding interdisciplinary project in which we have used spectroscopy to look at the materials used to illuminate 7-12th century manuscripts.

Host: Peter R. Ogilby

07.11.2013 Prof. Stephen Faulkner

"Boxing Clever, or Just Boxed In? Exploring and exploiting coordination in kinetically stable complexes"

Stephen will discuss the application of lanthanide coordination chemistry  and spectroscopy in the development of kinetically stable complexes that can be used as building blocks for the construction of more complicated structures. These can be used for targeted delivery of imaging agents to specific cell types, or as components of complexes that interact with anionic guests or with molecules of biological interest such as oxygen. Self-assembly of polynuclear complexes with anionic guests will be explored in detail, focusing on the use of remote substituents to exercise conformational control  of the binding pocket, and exploring whether there is such a thing as too much control.

Vært: Peter R. Ogilby

05.11.2013 Specialized Lecture Edward C. Monahan

Edward C. Monahan

Laboratory Studies of Primary Marine Aerosol Production

Useful characterizations of the physical nature, and flux from the sea surface, of the primary sea-salt aerosols have been obtained from a series of laboratory studies, most involving the production of realistic breaking waves in tanks with enclosed head spaces and the subsequent monitoring of the sea-salt aerosol injected into the head space as the bubbles resulting from each such breaking wave rise to the saltwater-air interface and burst. By relating these results to the initial area of the whitecap (foam patch) formed by the breaking wave, it is possible to extrapolate such laboratory results to the global ocean. This linking of laboratory results to the global ocean requires a knowledge of the whitecap climatology of the world’s oceans. The results of these laboratory studies defining  primary marine aerosol production as a function of whitecap coverage (and hence wind speed) have proven useful to regional and global climate modelers.

Host: Merete Bilde

31.10.2013 Specialized Lecture Jens B. Ravnsbæk

Shaken – not stirred! - Polymer chemistry and sensor material fabrication enabled by mechanochemistry.

The activation of chemical reactions by mechanical force, i.e. mechanochemistry has been known and utilized for centuries. Within the field of organic synthesis, ball-mill promoted mechanochemistry has recently seen a rapid increase in utility and now includes many important organic transformations. These solid-state mechanochemical reactions are typically fast, simple and offers high yields.

In this talk, I will present a novel solid-state polymerization promoted by ball milling. This method provides a rapid, easy and solvent-free route to conjugated polymers. This method has found great application in a one-pot, solid-state fabrication of polymer composite materials. Solid-state polymerization of poly(phenylene vinylene)s in the presence of single-walled carbon nanotubes provides a direct route to selector-varied polymer composite materials. This method allows for a rapid and easy preparation of composite materials that can be utilized in abrasion-based sensor fabrication. These results and the very recent progress in the development of a wireless, non-line of sight platform based on RFID technology and chemi-resistive sensors will be presented in this talk.

Vært: Kim Daasbjerg 

30.05.2013 Robert J. McMahon

Mechanistic Organic Chemistry of Harsh Reaction Environments

Our research efforts focus on elucidating the chemistry and spectroscopy of organic species that are postulated to play a role in harsh environments (e.g. combustion, planetary atmospheres, interstellar space).  These environments contain a remarkable diversity of organic functionality, including reactive intermediates such as anions, radicals, and carbenes.  We have drawn on our knowledge of mechanistic and structural organic chemistry to identify chemically-significant targets for detection and characterization.  Many of these investigations are made possible through our ability to prepare specific chemical precursor molecules via synthetic organic chemistry.  I will present case studies that exemplify how modern physical-organic chemistry spans the disciplines of organic chemistry, chemical physics, and astronomy. 

Vært: Peter R. Ogilby

23.05.2013 Per-Ola Norrby

Sustainable Catalysis

In a future sustainable society, all needed materials must be made in sustainable processes. We can only use renewable resources in energy-efficient reactions, and must not produce environmentally damaging waste. To meet these demands, new chemistry must be developed. The current talk will include examples from projects aimed at enable the use of environmentally benign catalysts, and from our first attempts at direct biomass conversion.

Vært: Troels Skrydstrup

16.05.2013 Thomas Bein

Multifunctional Mesoporous Nanoparticles for Targeted Drug Delivery

Mesoporous materials have attracted great interest in the context of bio-applications. Their high pore volume, regular pore structure, controlled morphology and diverse possible molecular functionalities can be combined in numerous ways to address important bio-applications such as stabilization of enzymes or controlled and targeted drug release. We will discuss the power of multifunctional mesoporous silica nanoparticles (MSN)[1,2] for storing and releasing bioactive compounds. We will cover different strategies for encapsulation and release using triggers such as changes of temperature, pH, redox-potential, or light intensity. Moreover, the uptake of such particles in cells will be explored, with an emphasis on optical single particle tracking experiments.   

For example, in recent work we have developed a polymer-based modular porous nanosystem that features, simultaneously, pH-sensitive release, cell targeting and long term stability.[3] To the surface of the amino-functionalized shell of our core-shell MSN particles, a heteroaromatic polymer was attached as a pH-sensitive cap system. At pH values of ~7 or higher, this polymer is hydrophobic and blocks the pores, whereas at acidic pH it is solvated and allows the release of a drug. Furthermore, we used poly(ethylene glycol) (PEG) as solubilizer, folic acid as targeting ligand and a red light photosensitizer for triggering endosomal escape. Release in HeLa cells was studied by confocal fluorescence microscopy, whereas targeting experiments were conducted in KB cells. Long-term stability tests of our silica-polymer composite material were performed in simulated body fluid at different pH-values. Under these conditions, no degradation of the mesoporous silica host could be observed, whereas with unfunctionalized silica strong degradation occurred. Our results show the great potential of this polymer-capped system for targeted drug delivery.

Acknowledgement. The authors are grateful for funding from DFG through the SFB 749, the NIM cluster and the “Fonds der Chemischen Industrie”.

[1] J. Kecht, A. Schlossbauer, T. Bein, Chem. Mater. 2008, 20, 7207.

[2] C. Cauda, A. Schlossbauer, J. Kecht, A. Zürner, T. Bein, J. Am. Chem. Soc. 2009, 131, 11361.

[3] S. Niedermayer, V. Weiß, A. Schmidt, C. Bräuchle, T. Bein, to be submitted

Vært: Peter R. Ogilby

02.05.2013 Dirk Trauner

Red colorants have played a prominent role in the history of organic chemistry and
continue to drive new developments in science. Azobenzenes, for instance, were first
described by Mitscherlich in 18341 and gave rise to an important class of dyes that are
still in wide use. In recent years, their ability to reversibly change configuration upon
irradiation has led to many useful applications in biology and the material sciences.
I will describe how azobenzene photoswitches can be used to control biological function with the spatial and temporal precision that only light provides.
Red sandalwood has been valued for millennia, particularly in China, where it was once reserved for the furniture of the imperial household.
Chemical investigations of its colored constituents started with Pelletier’s pioneering studies in 1814.2 I will present our own studies on the subject, which culminated in an efficient, biomimetic synthesis of the major colorants of red sandalwood, such as santalin A.
Our syntheses demonstrate that complex molecular scaffolds, not easily accessed with other methods, can be assembled along biosynthetic lines but without the necessity of enzymatic catalysis.

1) Mitscherlich, E. (1834), Ann. Pharm., 12: 311–314.
2) Cited in Poggendorf'?s Ann. Phys. Chem. 1833, 29, 102–107.

Vært: Thomas B. Poulsen

28.02.2013 Merete Bilde

Merete Bilde

Atmospheric Aerosols

Atmospheric aerosols affect human health, air quality and global climate. They are small (nano- to micro-meter sized) particles surrounded by air.
The particles are complicated structures presenting a wealth of scientific challenges; the particle phase can be solid, liquid (or both) with a highly complex chemical composition and a constant exchange of molecules with the gas phase.
In this talk I will discuss the formation, properties and impact of atmospheric aerosols in general and present our work on the chemico-physical properties of aerosol particles.

Vært: Karl Anker (konstitueret Institutleder)


21.02.2013 Willem H. Koppenol

Mechanisms of Oxygen Toxicity

We need oxygen to live, but we should not forget that it is toxic.  The toxicity of oxygen involves its partial reduction: initially, iron was thought to catalyse the formation of hydroxyl radicals from hydrogen peroxide, and while this mechanism may operate under certain conditions, later it was shown that peroxynitrite, formed from superoxide and nitrogen monoxide, was responsible for oxidation and nitration of biomolecules.  In principle, protective proteins such as superoxide dismutase and catalase, and antioxidants, such as as ascorbate, vitamin E and glutathione, are sufficient to protect or repair oxidative damage.  However, these defense mechanisms are overcome near activated macrophages and neutrophils.  The initial damaging event, the one-electron oxidation of a surface amino acid of a protein, has been investigated, but repair has not, until now.  Often, the site of radical attack is repaired by another amino acid within the protein, a process whereby a new radical is created.  Our studies also pertain to “normal” electron transfer, as from a cysteine, across a distance of 35 Å, to a high-valent iron complex in ribonucleotide reductase.  New values for the electrode potentials of tryptophan and tyrosine help to understand this process and to bring these separate areas of investigation – normal and abnormal electron transfer - together. 

The question really is whether a protein radical can be reduced before O2 reacts with it to form a peroxyl radical, often a diffusion controlled reaction.  While ascorbate and urate can reduce a protein radical rapidly, and thereby “repair” the protein, glutathione reacts too slowly.  Furthermore, thiyl radicals can oxidise nearby C-H bonds, which adds to the problem, rather than alleviating it.

Vært: Ove Christiansen 

14.02.2013 Barry Carpenter

Do we fully understand what controls selectivity in chemistry?

In the conventional view of selectivity in kinetically controlled reactions, product ratios are completely predictable from the relative standard-state activation free energies of the competing paths.  In this lecture it will be argued that, for many reactions, the activation free energies are not relevant quantities for determining selectivity.  The processes for which this will be the case are those in which the reaction path bifurcates after a transition state or for which nonstatistical dynamical effects are important.  The consequences can be profound for our understanding of reaction mechanisms.

Vært: Karl Anker Jørgensen