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Our research topics

(For publications see our list of publications, for fancy graphics please scroll down ;-)

These research projects are currently supported by grants from the National Science Foundation (Chemistry Division) and the Heavy Element Chemistry program of the office of Basic Sciences of the US Department of Energy’s Office of Science.
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Many of these project involve collaborations with other researchers – often experimentalists – at UB, elsewhere in the US, and internationally.

Why is this interesting and important?

Quantum Mechanics makes it possible to predict, theoretically, from first principles the behavior of atoms, molecules and solids, i.e. the properties of the atomistic building blocks of everything around us. Solving these equations (with some necessary approximations) requires serious number crunching. Recent advances in computer technology and algorithm development have allowed for the computation and theoretical prediction of the structures and properties of, for example, biomolecules, nano-materials and catalysts. These calculations are of great importance in science for (at least) three major reasons:

Our research is primarily focused on predicting and understanding optical and spectroscopic properties of molecules. This is very important: In spectroscopy, scientists study molecules by placing them in static or oscillating electric or magnetic fields of varying frequency and detecting the molecule’s response to the presence of these fields. These spectroscopic methods are among the most powerful tools available to scientists to investigate molecular structure, bonding within molecules, interactions between molecules, their dynamical behavior, and how all this related to the desired functionality and chemical behavior. There are numerous spectroscopic methods available, depending on the choice of the fields, each one being governed by a different molecular response parameter that can be both measured and calculated. Many interesting properties of advanced materials are also described by such response parameters.

Quantum Chemistry Software

Performing calculations as described above requires quantum chemistry software. The Autschbach research group is active in developing new functionality. In particular, we are active contributors to the open-source NWChem quantum chemistry package, and to the Amsterdam Density Functional and Molcas programs.

Research examples

(this section is steadily growing but not yet complete)

NMR (Nuclear Magnetic Resonance)

Catalysts: We are very interested in catalysts and co-catalysts for which molecular geometry and reactivity are poorly understood, but where it would have tremendous impact if they could be improved in a rational design process. As an example, together with our collaborator Dr. Monika Srebro, we have studied how Titanium NMR chemical shifts and nuclear quadrupole coupling parameters (observed, for example, by solid-state NMR) of half-titanocene pre-catalysts depend on the local structure and bonding around the Ti center. See publication [198].

Platinum anti-cancer drugs: cis-platin is a square planar Pt complex that is used to treat various types of cancer.
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(images from Wikipedia)
This and related compounds have very interesting NMR parameters, in part because of relativistic effects at the Pt center. It may be possible to utilize the Pt chemical shift, ligand chemical shifts, and the Pt–N J-coupling constants to monitor how the structure of the complexes change as they react with DNA and other molecules. However, there are also plenty of water molecules around and therefore it is important to know how these water molecules influence the NMR parameters. We have carried out several theoretical studies of cis-platin, cis-platin derivatives, and Pt complexes with 6 ligands and used a combination of ab-initio molecular dynamics and relativistic calculations of NMR parameters to determine the impact of water solvent molecules on the NMR parameters of the complexes. One surprising result: half of the magnitudes of the Pt–N J-coupling constants are due to the presence of the water molecules. Therefore, when the complex reacts and binds to DNA it would be vital to consider this effect before drawing any conclusions from measurements of the Pt–N J-couplings. See publications [156], [155], [127].

One problem with anti-tumor agents such as cis-platin is that they tend to be rather toxic, and only a small amount of what enters the body gets to work on the tumor where the toxicity is welcome. A new class of Pt-azido complexes have shown promise as photo-activatable anti-tumor agents. The azido ligand (N3-) is not very stable. This property can be used to convert a tumor-inactive (and less toxic) Pt-azido compound into an active one by shining light of a certain color onto the tumor region. We investigated the very unintuitive NMR parameters of these azido complexes. See publication [177],

Nanotubes and fullerenes: Together with my colleague Eva Zurek, for a number of years we have investigated 13C NMR chemical shifts in carbon based materials such as fullerenes and single-walled nanotubes (SWNTs). The images below show graphical representations of the NMR shielding tensors for C60 and for a finite (9,0) zig-zag nanotube:

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It was very exciting when we were the first team to predict the NMR shift of a carbon nanotube from first principles (ab-initio quantum theory) and an experimental paper confirming the prediction appeared just a few months later in the same journal. Subsequently, we investigated the dependence of the chemical shifts depending on the nanotube diameter and the effects of chemical functionalization. See publications [149] [141] [119] [105] [94] [90] [71] [31] for details and related work.

Metal-metal bonded systems: For many years we have studied NMR parameters of metal-metal bonded systems, in particular with very heavy transition metals where relativistic effects really play a big role. Examples are the following publications:
[47], [30], [27], and [20] for studies of Pt–Tl bonded systems.

A particularly interesting but also challenging system for NMR calculations, with metal-metal bonds but also being a super atom, is [Pt Pb12]2-. See publication [157].

Models for analyzing NMR chemical shifts and other NMR parameters NMR shifts and other magnetic properties can be analyzed rather intuitively by using ‘orbital rotation models’. The concept, and the action of a magnetic field on atomic s, p, d, and f-orbitals is explained
on this page (please follow this link).

Optical Activity

Much of our research is concentrated on understanding Optical Activity of chiral molecules. When synthesized, such molecules come in pairs that are mirror-images of one another with different optical properties, and they can be separated into samples containing pure forms of these mirror images. The technical terms are that these molecules have a ’handedness’ (’chirality’, from the Greek word for hand, as our left and right hands are mirror images of one another and nor ) and can be separated into two distinct enantiomers with different ’chiro-optical’ properties. Most bio-chemically active molecules are also chiral.

There is a separate page on optical activity and light polarization on our www-server (please follow the link).
You can also find some Mathematica-generated animations on that page, explaining linear and circular polarization of light and what happens when a chiral molecule interacts with light.

This research project has several facets. We were among the first to develop reliable computational methods for calculating electronic optical activity (optical rotation, circular dicroism). A summary of the formalism within a Time-dependent Density Functional Theory framework can be found in publication [165] Developments are on-going. Second, there is the question of how molecular structure and bonding relates to the observed optical activity. This is not an easy problem! Third, there are many applications of such computations, to help assigning absolute configurations or assign a CD spectrum, or find out how solvent may interfere with the observed optical activity.

We also have a very active collaboration with an experimental group on the optical properties of chiral organo-metallic complexes with helical organic groups.

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The graphics above has been composed from data generated during a study of the unusually large optical activity of norbornenone (publication [179]). Electron delocalization id an important factor that determines the magnitude of the optical rotation of this molecule. The green/red surfaces are graphical representations of the optical rotation tensor for this molecule.

Heavy elements

We implemented new functionality for calculations of NMR and EPR parameters in NWChem, see publications [168] [161] [136] . The figure below shows graphical representations of the electric field gradient in uranyl and a uranyl carbonate complex, calculated with an exact two-component (X2C) Hamiltonian. There is a sign change upon equatorial coordination of uranyl which we showed to originate, in part, by electron donation from the equatorial oxygen ligands to a U 5f orbital.

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 2011 – 2014 J. Autschbach. The material shown on this web page is in parts based on the results of research funded by grants from the National Science Foundation (NSF, grants CHE 0447321 (2005 – 2011, 0952253 (2010 – 2014), 1265833 (2013 – 2016)), by the Heavy Element Chemistry program of the US Department of Energy, Office of Science, Basic Energy Sciences (grant DE-FG02-09ER16066 (2009 – 2015)), as well as educational projects supported by these grants. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of these funding agencies.

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