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Group seminars

Each Friday CoopCat group holds on-line seminars during the coronavirus outbreak. Please let mail if you would like to join us!

Upcoming seminar: Friday, 23.10.2020, 10 am
dr Dariusz Piekarski
“Insight into the Folding and Cooperative Multi‐Recognition Mechanism in Supramolecular Anion‐Binding Catalysis”

Recent seminar: Friday, 16.10.2020, 10 am
dr Michał Kochman

“Modeling solvent effects in the photophysics of organic molecules”

CoopCat group has new members!

Dr Michał Kochman and dr Dariusz Piekarski received PD2PI grants to carry out research in CoopCat group. Michał will look on trans-cis photoisomerization of retinoids using quantum chemical methods. Darek will focus on machine learning design of anion binding catalysts.

James Pogrebetsky started PhD project with us. He will work together with Aleksandra to develop new embedding scheme to represent metallic surfaces.

UV-VIS of [2Fe-2S] cluster computed with CI approach for the first time

Adam’s work on [2Fe-2S] cluster is out:

Characterization of charge transfer excited states in [2Fe–2S] iron–sulfur clusters using conventional configuration interaction techniques

The experimental UV–Vis spectra of the biologically relevant [2Fe–2S] iron–sulfur clusters feature typically three bands in the 300–800 nm range. Based on ground-state orbitals and using the one electron transition picture, these bands are said to be of charge transfer character. The key complication in the electronic structure calculations of these compounds are the antiferromagnetic coupling of the iron centers and high covalency of Fe–S bonds. Thus, the examples of the direct computations of electronically excited states of these systems are rare. Whereas low lying electronic excited states were subject of recent studies, higher energy states computed with many-body theories were never reported. In this work we present, for the first time, calculations of the electronic spectra of [Fe2S2](SMe)2−4 biomimetic compound. We demonstrate that spin-averaged restricted open-shell Hartree–Fock orbitals are superior to high-spin orbitals and are convenient reference for subsequent configuration interaction calculations. Moreover, the use of conventional configuration interaction methods enabled us to study the nature of the excited states in details with the difference density maps. By systematic extension of the donor orbital space we show that key excitations in the 300–800 nm range are of Fe 3d ← (μ-S) character.

More on GO-porphyrin is out

Check our latest paper on GO-porphyrins interface. Our contribution includes structure and spectra simulations, explanation of exp-observed peaks as well as charge-transfer study in the nanohybrid using high-level multireference methods (CASSCF/DLPNO-NEVPT2).

Interaction of Light with Non-Covalent Zinc Porphyrin-Graphene Oxide Nanohybrid

The present study explores the influence of graphene oxide (GO) on deactivation pathways of the excited states of zinc 5,10,15,20-tetrakis(4-(hydroxyphenyl) porphyrin (ZnTPPH). The interaction of light with free ZnTPPH molecules and with ZnTPPH molecules adsorbed on graphene oxide sheets was probed via UV-Vis spectroscopy, fluorescence spectroscopy, femtosecond pump–probe spectroscopy and nanosecond flash photolysis. Formation of the ground-state ZnTPPH-GO complex in solution was monitored by the red-shift of the porphyrin Soret absorption band. It was found that Stern−Volmer fluorescence quenching can be described in terms of two different quenching regimes depending on the GO concentration. In addition, our comprehensive analysis of the steady-state and time-resolved emission experiments led to the conclusion that the observed quenching was entirely attributable to a static mechanism. Laser flash photolysis showed that the triplet lifetime of the ZnTPPH was increased in the presence of GO from 174 µs to 292 µs, which is related to the decrease of the rate constant of a radiationless decay mechanism involving rotation of the peripheral hydroxyphenyl rings of the porphyrin. Femtosecond transient absorption spectroscopy demonstrated the presence of a fast photoinduced electron transfer from the singlet excited state of ZnTPPH to the GO sheets, as indicated by the formation of a porphyrin radical cation. Quantum chemical calculations were used to gain deeper insights into the nature of the electronically excited states in the ZnTPPH-GO complex.

New paper published

Magda’s work in collaboration with Emil and Ania from R. Nowakowski group has been published!

Effect of unimodality and bimodality of Pd nanoparticles on the catalytic activity of Pd/SiO2 in the removal of diclofenac from water

In this work, we investigated the catalytic performance of uni- and bimodal Pd/SiO2 catalysts in the aqueous phase hydrodechlorination (HDC) of diclofenac – a very popular nonsteroidal anti-inflammatory drug. Unimodality and bimodality was confirmed by temperature-programmed hydride decomposition (TPHD) and TEM. The highest activity and 100% efficiency in batch and flow mode were observed for bimodal Pd NPs. This outstanding efficiency could be attributed to the close coexistence of small and large metal nanoparticles with different affinity to hydrogen and chloroorganic compound. The obtained results encourage discussion on the necessity to strive for perfect unimodal catalysts for the HDC processes.

New paper is out!

Tuning Nano‐Nickel Catalyst Hydrogenation Aptitude by On‐the‐Fly Zirconium Doping

The effect of nano‐Ni catalyst post‐synthetic Zr‐modification on hydrogenation reaction of 6‐methyl‐5‐hepten‐2‐one was investigated in a fixed bed continuous‐flow micro‐reactor to produce fine chemicals. The catalytic performance revealed that Zr‐doping achieved by surface organometallic chemistry approach modifies the natural aptitude of nickel to hydrogenate C=C bond, since the addition of small quantities of zirconium significantly increased the amount of unsaturated and saturated alcohols formed in 6‐methyl‐5‐hepten‐2‐one hydrogenation. Quantum chemical calculations revealed a stronger interaction between Zr←O=C that promotes the formation of C=C semihydrogenation product and enhances the probability of complete hydrogenation. The on‐the‐fly strategy presented herein enables for rapid optimization and understanding of catalytic processes.