✎ animation:seminaires:2017:accueil[CBP]

✎ animation:seminaires:2017:accueil
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  * [[animation:evenements|Évènements scientifiques]]

====== Séminaires/Colloquium 2017 ======

===== Computational photochemistry of complex molecular systems =====
{{:cbp_ens.jpeg?nolink&200 |}}**07 mars 2017 de 11h30 à 12h30** \\
COLLOQUIUM Centre Blaise Pascal-Laboratoire de Chimie \\
Grande salle du CBP (LR6 C 023), ENS Lyon, France \\

**Martial Boggio-Pasqua **, Laboratoire de Chimie et Physique Quantique, Université Paul Sabatier Toulouse
 \\

Organisateurs : \\ 

  * Ivan Rivalta (Laboratoire de Chimie, ENS de Lyon) \\
  * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon, France) \\
   **(25 participants)**
**
Abstract :** \\ 
In the past three decades or so, computational photochemistry has gained considerable credit as a tool to investigate photochemical reaction mechanisms in organic, inorganic and even biological chromophores.[1] This reputation has been gained thanks to the concomitant growth of computational power and theoretical developments in the field of quantum chemistry. These advances allow peering beyond the traditional interpretations of photochemistry focused on vertical excitations at the Franck–Condon geometry. The exploration of other regions of the complex multidimensional potential energy surfaces is becoming routine in small- and medium-sized molecular systems, and the synergy between accurate and global static calculations and either quantum or semiclassical nonadiabatic molecular dynamics simulations has allowed major breakthroughs in the understanding of photochemical and photophysical processes.
In this seminar, I will present some results of computational studies performed in our group on photochromic organic and inorganic compounds. In particular, dihydropyrenes (DHPs) derivatives, ruthenium sulfoxyde and nitrosyl complexes, for which complex photoswitching mechanisms have been invoked,[2–5] have focused our attention in recent years. In addition to their photochromic properties, DHPs and ruthenium nitrosyl complexes present a rich photochemistry. DHPs can photosensitize molecular oxygen and thermally release singlet oxygen,[6] while ruthenium nitrosyl complexes can photorelease nitric oxide.[7] I will show how advanced computational photochemistry can help to rationalize the photochemical behavior of such compounds.[8–13]

**References:** \\ 
  - (a) A. G. Kutateladze (Ed.), Computational Methods in Photochemistry, CRC Press, 2005. (b) M. Olivucci (Ed.), Computational Photochemistry, Elsevier, 2005.
  - M. A. L. Sheepwash, R. H. Mitchell, C. Bohne, J. Am. Chem. Soc. 2002, 124, 4693.
  - M. Boggio-Pasqua, M. J. Bearpark, M. A. Robb, J. Org. Chem. 2007, 72, 4497.
  - (a) B. A. McClure, N. V. Mockus, D. P. Butcher Jr., D. A. Lutterman, C. Turro, J. L. Petersen, J. J. Rack, Inorg. Chem. 2009, 48, 8084. (b) B. A. McClure, J. J. Rack, Inorg. Chem. 2011, 50, 7586.
  - (a) B. Cormary, S. Ladeira, K. Jacob, P. G. Lacroix, T. Woike, D. Schaniel, I. Malfant, Inorg. Chem. 2012, 51, 7492. (b) L. Khadeeva, W. Kaszub, M. Lorenc, I. Malfant, M. Buron-Le Cointe, Inorg. Chem. 2016, 55, 4117.
  - S. Cobo, F. Lafolet, E. Saint-Aman, C. Philouze, C. Bucher, S. Silvi, A. Credi, G. Royal, Chem. Commun. 2015, 51, 13886. 
  - (a) N. L. Fry, P. K. Mascharak, Acc. Chem. Res. 2011, 44, 289. (b) J. Akl, I. Sasaki, P. G. Lacroix, I. Malfant, S. Mallet-Ladeira, P. Vicendo, N. Farfán, R. Santillan, Dalton Trans. 2014, 43, 12721.
  - D. Roldan, S. Cobo, F. Lafolet, N. Vilà, C. Bochot, C. Bucher, E. Saint-Aman, M. Boggio-Pasqua, M. Garavelli, G. Royal, Chem. Eur. J. 2015, 21, 455.
  - M. Boggio-Pasqua, M. Garavelli, J. Phys. Chem. A 2015, 119, 6024.
  - A. J. Göttle, I. M. Dixon, F. Alary, J.-L. Heully, M. Boggio-Pasqua, J. Am. Chem. Soc. 2011, 133, 9172.
  - J. Sanz García, F. Alary, M. Boggio-Pasqua, I. M. Dixon, I. Malfant, J.-L. Heully, Inorg. Chem. 2015, 54, 8310.
  - J. Sanz García, F. Alary, M. Boggio-Pasqua, I. M. Dixon, J.-L. Heully, J. Mol. Model. 2016, 22, 284.
  - M. Boggio-Pasqua, M. López Vidal, M. Garavelli, J. Photochem. Photobiol. A 2017, 333, 156.
===== STRUCTURE, CHEMICAL ORDER AND REACTIVITY OF GOLD-PALLADIUM NANOPARTICLES: FROM VACUUM TO REACTION CONDITIONS =====
{{:cbp_ens.jpeg?nolink&200 |}}**19 janvier 2017 de 11h à 12h** \\
COLLOQUIUM Centre Blaise Pascal-Laboratoire de Chimie \\
Grande salle du CBP (LR6 C 023), ENS Lyon, France \\

**Hazar Guesmi**, Institut Charles Gerhardt – UMR5253-Equipe MACS ENSCM, Montpellier
 \\

Organisateurs : \\ 

  * David Loffreda (Laboratoire de Chimie, ENS de Lyon) \\
  * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon, France) \\

The knowledge of the composition and surface structure of nanoalloy particles is crucial to explain their catalytic performance. In addition, the bonding of adsorbates may, in some cases, induce modifications in local atomic composition and surface structure, changing the activity and selectivity of the catalyst. These facts were observed for Au-Pd nanoparticles (1,2). Indeed, although the gold surface enrichment is predicted to be thermodynamically favorable under vacuum conditions (3) , a reversed segregation of Pd as a more active component to the surface is reported to occur in the presence of adsorbates (4,5). 
In order to study how adsorption of CO molecules changes the surface composition of AuPd alloys, we develop a theoretical methodology which is able to take this effect into account (6) . An Ising model based on density functional theory calculations is derived to define interatomic potentials that describe metal–metal, metal–CO, and CO–CO interactions. Then, through the use of Monte Carlo simulations within the semi-grand canonical ensemble, the effect of adsorption-induced segregation for the AuPd(100) surface is well-reproduced for different temperatures and CO pressures. Segregation isotherms identify a Pd surface enrichment for low CO pressures, and CO surface saturation is reached at an intermediate coverage of θ = 0.5 ML. Furthermore, Pd chains induced by an ordering of adsorbed CO molecules appear at low temperature and intermediate CO pressures. These chains are the result of a competitive effect between CO–CO repulsions and metal–CO interactions

Références 

  - A. Hugon, L. Delannoy, J.M. Krafft, C. Louis, J. Phys. Chem. C 114 (2010) 10823.
  - H. Guesmi, Gold Bulletin 46 (2013) 213.
  - F. Pittaway , L.Paz-Borbün , RL. Johnston , et al., J. Phys Chem C 113 (2009)  9141.
  - H. Guesmi, C. Louis, L. Delannoy, Chem. Phys. Lett., 503 (2011) 97.
  - A. Dhouib, H. Guesmi, Chem. Phys. Lett., 521 (2012) 98.
  - B. Zhu,  J. Creuze, C. Mottet, B. Legrand and H. Guesmi, J. Phys. Chem. C 120 (2016) 350-359.