The IQC has an European exchange project (FP7-PEOPLE-2009-IRSES) with the Universidad de Guanajuato (UGTO) and VU University of Amsterdam (VUA), about “Chemical bonding and aromaticity in novel inorganic and organometallic clusters“. Within this project, I went to Guanajuato for a month together with dr. Mikael Johansson to work together with the group of Prof. Gabriel Merino. Our research stay here dealt with chemical bonding and aromaticity patterns in supermolecular flowers, and in novel organometallic clusters.

Prof. Marcel Swart, Abril Castro and dr. Mikael Johansson

The photo above shows both of us together with Abril Castro, a Master student from the group of Prof. Merino who will soon to be doing the reverse trajectory and be visiting Girona beginning of 2012. Given below are some typical pictures of Guanajuato, with a more elaborate photographic description available at:
Mikael Johansson’s website and my blog.

The IQC was well represented at the XXXVII Congreso de Químicos Teóricos de Expresión Latina (Quitel), which was held at a superb hotel in Riviera Maya (Mexico). Four members of the IQC (dr. Sílvia Osuna, dr. Ferran Feixas, dr. Eduard Matito and myself) gave a presentation about their recent work (unfortunately, mine had to be cancelled at the last minute due to flu; bad airco), three of which were invited lectures: “THE ROLE OF DISPERSION IN FULLERENE REACTIVITY”, “NEW APPROXIMATION TO THE N-ORDER REDUCED DENSITY MATRIX AND ITS APPLICATION TO MULTICENTER BOND INDICES”, “CHEMICAL BONDING AND AROMATICITY FROM ELECTRONIC DELOCALIZATION DESCRIPTORS” and “CHEMICAL BONDING IN SUPERMOLECULAR FLOWERS”. The conference was well situated as can be seen in the picture below:

Members of IQC at Quitel conference

But also the science was good, with prior to the Quitel conference a workshop of ADF (which I had been invited to lead), and many renowned speakers at the conference: Carlo Adamo, Roberto Car, Clemence Corminboeuf, Fernando Cossío, Francesc Illas, Todd Martinez, Michele Parinello, Maria Ramos, Gus Scuseria, Alejandro Toro-Labbé and Jesus Ugalde, to name just a few. Unfortunately, I had to miss most of them, but was lucky enough to see the talk by Jesus Ugalde: it was the first time I’ve seen him present actual chemistry, and similar to the previous talks I’ve seen on method development it was a splendid talk.

Together with Eduard Matito I was also able to meet dr. Kallol Ray, from the Humboldt Universitäaut;t Berlin, who was attending another conference on (bio)inorganic chemistry some 40 km away from our location.

Eduard Matito and MS meeting with Kallol Ray and his wife, in Playa del Carmen

Finally, some more pictures of the hotel, another hotel nearby (Molcas) that apparently deals with quantum-chemistry, and an impression of the ADF workshop:

Location of Quitel conference

One of the many pools at the hotel

Hotel dealing with quantum chemistry

ADF workshop at Quitel

α-diimine iron complexes have been suggested to catalyse polymerisation via two distinct pathways, depending on the spin state of the iron complex, thus being among the first non-biological catalysts exploiting the spin-state of a transition metal to do their magic. In what began as a HPC-Europa2 project, we have studied a typical complex of this family, ^R”[N,N]FeCl₂, with [N,N] = Cy–NCR”–CR”N–Cy (Cy = cyclohexyl). Three different R”-groups have been considered: PhF (para-fluorophenyl), PhOMe (para-methoxyphenyl), and PhNMe₂ (para-dimethylaminophenyl). With electron-withdrawing R”-groups (PhF, PhOMe), polymerisation proceeds as a catalytic chain transfer (CCT) mechanism, while the electron-donating PhNMe₂ takes an atom transfer radical polymerisation (ATRP) pathway.

Using the for spin-states reliable SSB-D functional, we see that, contrary to previous suggestions, the spin-states of the complexes involved are not affected by the R” group. Instead, the different behaviour arises from a subtle interplay between the electron-withdrawing or donating character of phenyl substituents and the iron centre, and small but crucial differences in the reorganisation energies affected during the reactions. In addition, we provide an alternative explanation of the measured magnetic moments, consolidating the experimental and theoretical findings. Read all about it in M. P. Johansson, M. Swart, “Subtle effects control the polymerisation mechanism in α-diimine iron catalysts“, Dalton Transactions.

In the middle of March (13-14th), Prof. Marcel Swart visited the group of Prof. Abhik Ghosh, at the Centre for Theoretical and Computational Chemistry in Tromsø. Not only is this centre located at the city with the most northern university in the world, Tromsø is also the capital of the Arctic and has a remarkable modest climate (because of the North Atlantic Current that brings relatively warm water northwards, and as a result, the coastal area of the city has winter temperatures of on average -2 degrees Celsius). The difference between Girona and Tromsø was however big, with nice spring weather in Catalunya and snow in Tromsø (as can be seen in the pictures below).

Tromsø covered in white

View from office of Prof. Ghosh

Mountain-side in Tromsø

Dr. Swart gave a presentation about “Improved density functional for biological applications (SSB-D)” and discussed the research currently taking performed in Tromsø, and talked with Prof. Ghosh about a collaboration on transition-metal complexes. Both Profs. Ghosh and Swart are very interested in spin-states, for instance those of metalloporphyrins and related compounds. A number of recent papers by both groups have shown the importance of the OPBE/OLYP density functionals (see e.g. the publications of Prof. Ghosh or the publications of Prof. Swart), as well as the more recent SSB-D functional.

We have recently held the first of an annual online poll for favorite density functionals in order to obtain a popularity adapted consensus object (PACO), as announced in a previous entry.

This “consensus” PACO functional may serve as a measure of how well the computational chemistry community is doing if compared to state-of-the-art reference data.

It will change over time and hopefully will result in gradual improvements. To track the performance of the PACO functionals, it is checked for a variety of diverse interactions: atomization energies of six representative molecules (AE6), barrier heights of hydrogen-transfer reactions (BH6), π-π stacking of anti-parallel cytosine dimer, spin-state splittings of FeFHOH and Ni(EDT)₂^2–, excitation energies (singlet, triplet) of CO, and hydrogen-bonding in four dimers (ammonia, water, formic acid, formamide). These small systems are studied using basis sets close to the basis set limit, and compared to either coupled cluster results or experimental data.

A surprising result from the poll was that the widely-used B3LYP is in fact not the most popular density functional, but came only second after PBE0 (also known as PBE1PBE).

More information can be found in the news-item and the popularity poll webpage.

In many redox-active enzymes, electron transfer (eT) is due to tunnelling. In collaboration with the University of Helsinki and the National Institutes of Health, Bethesda, we show that the haem to haem eT in cytochrome c oxidase (CcO), the terminal respiratory enzyme, exhibits an exceptionally low reorganisation energy. Independent molecular dynamics and quantum-chemical modelling  indicate that the energy penalty of structural reorganisation is only 0.2 eV upon eT, while the “standard” value lies around 0.7 eV. The rate of eT can, however, still be modelled by the Moser-Dutton formulation, if reinterpreted as the average of individual eT rates between all atomic donor/acceptor pairs, using individually determined packing densities. In the paper Interheme electron tunneling in cytochrome c oxidase, the implications of the findings are discussed in detail. Read all about it in the Proceedings of the National Academy of Sciences.

The two haems of CcO

The tribunal assigned by the Consell de Govern of the University of Girona that had to decide on the Outstanding Awards of Doctoral Studies in Chemistry 2009 has decided to award it to Mireia Güell. She defended her PhD thesis entitled “Theoretical Studies of Systems of Biochemical Interest Containing Fe and Cu Transition Metals” end of July 2009 and obtained the grade excel·lent cum laude. Her PhD supervisors were Dr. Miquel Solà, Dr. Josep Maria Luis and Dr. Marcel Swart.

The IX Girona Seminar has been a pioneering conference in the sense that new communication technologies were incorporated in order to open it to anybody in the net. In this way, from today it is possible to watch any of the given talks of the Seminar by just connecting to this link and searching for a specific scientist or topic. Enjoy the high scientific level met in Girona this last summer.

This week a number of applications for computer time have been awarded (all with M. Swart as principal investigator): for more information see the BSC and the Cesca websites.

For the period of November to end of February two new projects at MareNostrum have been given: 245.760 hours for the project “Spectroscopy and reactivity of copper proteins” (M.P. Johansson and M. Swart), and 176.640 hours for “Exploring the exohedral reactivity of the metallic carbide endohedral metallofullerene Ti₂C₂@D_3h-C₇₈” (M. Garcia, S. Osuna, J.M. Luis, M. Solà and M. Swart).

Today also a project for testing of the new SGI Altix UV 1000 machine at Cesca has been awarded to study the NMR of water clusters (M. Solà and M. Swart), 100.000 hours to be spent before the end of December 2010.