Method comparison against exp. data

1. A B3LYP Study on the C-H Activation in Propane by Neutral and +1 Charged Platinum Clusters With 2-6 Atoms T. Cameron Shore, Drake Mith, Doug DePrekel, Staci McNall, and Yingbin Ge* Department of Chemistry, Central Washington University, Ellensburg, WA 98926 + Propane (C3H8) Propene (C3H6) Introduction Global optimization of Pt clusters (e.g. Pt5) Potential energy surface (Pt5 + C3H8) Pt10 and Pt10+ local minima + C3H8 • Vajda et al. find Pt8-10 clusters are much more active than traditional catalysts towards propane in 4 steps1: • Ptn + C3H8 → H−Ptn−CH(CH3)2 • H−Ptn−CH(CH3)2 → (H)2−Ptn−propene • (H)2−Ptn−propene + ½ O2 → Ptn−propene + H2O + heat • Ptn−propene + heat → Ptn+ propene • We studied the Ptcluster size and charge effects regarding the rate limiting step 1. Removal of a 2nd H produces propene Relative energies are in kJ/mol. M stands for multiplicity. Global minimum • Computational method • B3LYP density functional theory • 6-31G(d) on C and H • LanL2DZ (f) basis set and LanL2 effective core potential on Pt • Ptn + C3H8 → Ptn---C3H8 → H−Ptn−CH(CH3)2 Method comparison against exp. data Each label consists of point group, relative energy in kJ/mol, and # of imaginary frequencies if applicable. Energy includes electronic energy and zero-point vibrational energy. Mean absolute errors of calculated electron affinity, ionization energy, & bond energy Global minima of Pt2-6 Mean absolute errors of calculated bond distances • Conclusions • Pt2 is less active than larger Pt3-6 clusters. • +1 charged Pt clusters are more active than neutral ones. • Electron pushing surface hinders the catalytic ability of the supported Pt clusters; electron withdrawing surface is preferred. • Ptn+ + C3H8 → Ptn+---C3H8 → H−Ptn+ −CH(CH3)2 Global minimum vs. Local minimum δ Global minima of +1 charged Pt2-6 e- E local minimum local minimum Electron withdrawing surface • Acknowledgements • CWU SEED Grant • CWU College of the Sciences Faculty Development Fund • CWU Department of Chemistry local minimum global minimum Various Ptn structures Notes and References The following experimental data are used as the benchmark: the electron affinity (EA) of Pt and Pt2 are 205.0 kJ/mol and 183.1 kJ/mol, respectively; the ionization energy (IE) and bond energy (BE) of Pt2 are 864.4 kJ/mol and 303 kJ/mol, respectively; the bond energy of PtH is 332 kJ/mol; the ionization energies of PtC, PtO, and PtO2 are 912 ± 5 kJ/mol, 965 ± 10 kJ/mol, and 1095 ± 5 kJ/mol, respectively; the bond energies of PtC, PtO, and PtO2 are 574 ± 7 kJ/mol, 415 ± 12 kJ/mol, and 426 ± 13 kJ/mol, respectively; the equilibrium bond distances of Pt2, PtH, PtC, and PtO are 2.333 Å, 1.53 Å, 1.679 Å, and 1.727 Å, respectively. Vajda S, Pellin MJ, Greeley JP, Marshall CL, Curtiss LA, Ballentine GA, Elam JW, Catillon-Mucherie S, Redfern PC, Mehmood F, Zapol P (2009) Subnanometre platinum clusters as highly active and selective catalysts for the oxidative dehydrogenation of propane. Nat Mater 8:213-216 T.C. Shore, D. Mith, DePrekel, S. McNall, Y. Ge SA (2013) A B3LYP study on the C—H activation in propane by neutral and +1 charged low-energy platinum clusters with 2-6 atoms: A B3LYP study, Reaction Kinetics, Mechanisms and Catalysis, in press, 2013