1 / 28

WYJAZDY I WYST Ą PIENIA WAKACJE 2008

WYJAZDY I WYST Ą PIENIA WAKACJE 2008. Kanada, Vancuver, lipiec 2008 Australia, Sydney, wrzesień 2008 S ł owacja, Strbske Pleso, wrzesień 2008. WATOC 2008 Sydney, September 14-19 2008.

soren
Download Presentation

WYJAZDY I WYST Ą PIENIA WAKACJE 2008

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. WYJAZDY I WYSTĄPIENIAWAKACJE 2008 Kanada, Vancuver, lipiec 2008 Australia, Sydney, wrzesień 2008 Słowacja, Strbske Pleso, wrzesień 2008

  2. WATOC 2008 Sydney, September 14-19 2008 The World Association of Theoretical and Computational Chemists (WATOC) former: The World Association of Theoretically Oriented Chemists.

  3. IX. PANNONIAN INTERNATIONAL SYMPOSIUM ON CATALYSIS Strbske Pleso, Slovakia8 - 12   Sept. 2008

  4. THEORETICAL MODELING OF SMART CATALYTIC ACTIVITY OF COPPER CENTRES IN ZEOLITES: FROM ELECTRON DENSITY FLOW TOWARDS ACTIVATION Ewa Broclawik Pawel Rejmak Institute of Catalysis Polish Academy of Sciences Pawel Kozyra Joanna Zalucka Mariusz Mitoraj Faculty of Chemistry Jagiellonian University

  5. FeIVO Cu+, Ag+ + H O O – O Al Si O O O O „Smart catalysis” – very selective, fine chemistry supported by transition metal active centres in homogeneous, heterogeneous and enzymatic catalysis Enzymatic activity: heme and nonheme iron centres (cytochromes, oxygenases etc.) Zeolitic activity: exchanged transtion metal (Ag, Cu, Co) sites in zeolites (MFI, FAU, FER etc)

  6. Methodologies for theoretical (QM) studies: DFT modeling of stable structures, reaction intermediates and their physical properties for cluster models of zeolitic sites: relatively cheap method, reliable results but neglect of long-range interactions, discrimination between different types of lattices, Si/Al ratio or specific metal siting hardly possible QMPOT (Combined QM – Interatomic Potential Functions Method) – entire framowk considered, main drawabcks of cluster modeling eliminated but framework treated approximately (classical Force Fields), extra parametrization required Periodic models – in principle accurate forentire framowk but computationally demanding varying Si/Al ratio or metal loading breaks strict periodicity New theoretical concepts for interpretation – NOCV (Natural Orbitals for Chemical Valence): analyzis of electron density flow accompanying catalytic event

  7. SPECIATION OF COPPER SITES IN FAUJASITE (by interaction with CO probe) Small cluster models are not useful to mimic various envirinments in different zeolites (e.g. FAU, mordenite, ferrierite, ZSM-5) Local environments may be very similar but framework and site properties will differ QMPOT

  8. COMBINED QUANTUM MECHANIC – INTERATOMIC POTENTIAL FUNCTIONS METHOD (QMPot) 1)Periodicframework (O) - MM 2) Cluster (C) - QM 3)Link atoms (L) Etot = EMM(O) + EQM(C+L) + E(O,C,L) = EMM(O) + EQM(C+L) – EMM(C+L) + ΔQM/MM(O,C,L) ≈ ≈ EMM(O) + EQM(C+L) – EMM(C+L) (Eichler, U., Koelmel, C. M., Sauer, J. J. Comp. Chem. 1997, 18(4), 463) Sierka, M., Sauer, J. In: Yip., S. (Ed.), The Handbook of Materials Modelling, Part A Springer, Dordrecht, 2005, 241-258)

  9. FAUJAZITE (FAU) • Regular cell F-d3m, • 192 atoms T and 384 O • FAU – high alumina content • Xzeolite – Si/Al close to 1 • Y zeolite – Si/Al about 2-3 Possible cationic (black) and crystallographic O positions (gray) (Smith., J. V. Adv. Chem. Ser. 1971, 101, 171) Cu(I)-Y XRD and ND experimentsindicate Cu(I) only in I’, II or II’ positions (Palomino, G. T., Bordiga, S., Zecchina, A., Marra, G. L., Lamberti, C. J. Phys. Chem. B2000, 104, 8641) theoretical positions (red) – stability: II≈I’ >> III (Rejmak, P., Sierka, M., Sauer, J. – w przygotowaniu) Site I is not accessible for adsorbed molecules

  10. 2)The impact of embedding • The nearest environment of Cu+ ions in site II • (2 Al atoms in para positions) • (A) free cluster • (B) Force Fieldonly • (C) QMPot model • environment importance!! 4Al

  11. Summary for QMPOT modeling: • environment importance accounted for • no microscopic insight into electronic processes/ charge flow (need for new theoretical development) Interaction of benzene with Cu+, Ag+ i Na+ in ZSM-5 zeolite Experiment:J. Załucka, P. Kozyra, J. Datka Theory:M. Mitoraj, A. Michalak

  12. activation M7-Me-benzene (Me=Cu(I), Ag(I), Na(I)) 6,5 kcal/mol Eint = 19,2 kcal/mol 11,9 kcal/mol Adsorption by 2 carbon atoms C=C variation, aromaticity diminished for Cu(I) and Ag(I)

  13. Mechanism of C=C activation??? Donationorbackdonation???

  14. NOCV – Natural Orbitals for Chemical Valence(Mitoraj M., Michalak A., Organometallics, 26 (2007) 6576-6580) NOCV are the eigenfunctions of a valence operator: Vi(ri) = ii(ri) where: V=1/2(P – P0) P – charge and bond order matrix for the molecule P0 – charge and bond order matrix for promolecule– fragmentsin thegeometryof common systembut noninteracting i(ri)describes spatial distribution and character of elementary electron density flows („channels”) ithe share of a given “channel” in total density flow

  15. occupied molecular orbitals in composed system occupied „promolecular” orbitals “pairing property” of NOCV (rigorous proof by M. Radon): relation between eigenvalues of V and expectation values of the molecular density operator, P  • total electronic transfer may be decomposed into sum of separated transfers within pairs of coupled NOCV • for each k, the transfer of νkelectrons from ϕ−kto ϕ+korbital is observed • during this transfer the total number of electrons in (ϕ−k, ϕ+k ) pair remains equal exactly to two electrons Now:

  16. NOCV – Natural Orbitals for Chemical Valence(Mitoraj M., Michalak A., Organometallics, 26 (2007) 6576-6580) Decomposition of differential density flow: ρ(r)molekule/cluster - ρ (r)fragment1–ρ(r)fragment2 into elementaryflow channelsi(ri) The method to discriminate between donation and backdonation (evenσ orπ)!! -i*-i(ri)2+i*i(ri)2describes spatial distribution andcharacter of elementary electron density flows („channels”) i the share of a given “channel” in total density flow

  17. Example: heme + CO O C

  18. backdonation donation -0.105*44 -0.218* -0.356* -0.484* NOCV [M7-Cu+]-C6H6 yellow – electron outflow green– electron inflow

  19. [Cu+-zeo]-C6H6 [Cu+-C6H6]-zeo bond Cu-zeo [Cu+]-[C6H6]

  20. donation backdonation -0.160* -0.266* -0.217* NOCV [M7-Ag+]-C6H6

  21. [Ag+-zeo]-C6H6 [Ag+]-[C6H6] [Ag+-C6H6]-zeo

  22. Both donation and backdonation correlate with C=C activation measured by IR frequency shifts • Total charge change does not correlate positively with C=C activation • Na+ - only electrostatic interaction, no activation

  23. CONCLUSIONS • Cluster DFT modeling: • open path to advanced calculations • reasonable reproduction of experiment (for justifiedmodel) • rough understanding of physical nature of the process • Combined QM/MM modeling: • environment importance accounted for • detailed speciation/discrimination of sites • statistical interpretation of experimental results • New interpretative theoretical tools • microscopic insight into electronic processes/ charge flow

  24. Acknowledgments Polish State Committee for Scientific ResearchIR studies supported by grant NN204198733. Computational studies supported by:EU project Transfer of Knowledge TOK-CATA, contract MTKD-CT-2004-509832 grant N20418031/3999. grant PZB-KBN-116/T09/2004 Thanks to prof. J. Sauer and dr. M. Sierka (Humboldt University) for QMPOT code. Thank you for kind attention!

More Related