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SUMMARY:Electrostatic Catalysis  of Non-Redox Reactions
DTSTART:20170613T163000
DTEND:20170613T173000
DTSTAMP:20260601T105554Z
UID:ef70f3a30973a0888cc40d6d84b073de1873a2b182c6bfe1760033c6
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Michelle Coote \nAustralian National University\nAustra
 lia\nIt is well known that the rate of redox reactions can be manipulated 
 by means of an electrical potential gradient.  However\, in this talk we 
 will show that electrostatic catalysis is also a practical possibility for
  manipulating non-redox processes. As elegantly demonstrated by Shaik and 
 co-workers\, many formally covalent species can be stabilized by resonance
  between their covalent and one or more charge-separated mesomeric forms.1
  In principle\, if an electric field is oriented in such a way as to elect
 rostatically stabilize one of these minor contributors\, the amount of res
 onance will increase and the species will be stabilized accordingly. As an
  example\, Shaik and co-workers showed via quantum-chemical modelling that
  an oriented electric field (OEF) could be used to promote selectivity bet
 ween the exo and endo products of a simple Diels-Alder reaction\, and also
  lower the activation barriers.1b However\, for electrostatic catalysis to
  be achieved in practice\, the orientation of the reactants would have to 
 be controlled. Together with collaborators\, we have been using a combinat
 ion of theory and experiment to explore two alternative solutions to this 
 problem. The first is using surface chemistry techniques\, in conjunction 
 with the break-junction technique in scanning tunnelling microscopy\, to p
 robe unfavourable Diels-Alder chemical reactions (see Fig. 1).2 This allow
 s us to detect chemical reaction events at the single molecule level\, whi
 lst delivering an oriented electrical field-stimulus across the approachin
 g reactants. In the second approach\, we have instead addressed problem of
  orientation of the electric field by making use of appropriately placed c
 harged functional groups to provide the electrostatic stabilization for so
 lution-phase reactions.3 In this way\, the direction of the local field ex
 perienced by the reaction centre is fixed\, and by associating the stabili
 zation or destabilization with the protonation state of an acid or base gr
 oup\, it has the advantage of providing a convenient pH switch. In this ta
 lk our experimental and theoretical results will be presented and the broa
 der prospects for electrostatic catalysis discussed.\n\n1. (a) For a revie
 w see: S. Shaik\, D. Mandal\, R. Ramanan\, Nature Chem. 2016\, 8\, 1091-10
 98\; (b) R. Meir\, H. Chen\, W. Lai and S. Shaik\, ChemPhysChem\, 2010\, 1
 1\, 301–310\n2. A. C. Aragonès\, N. L. Haworth\, N. Darwish\, S. Ciampi
 \, N. J. Bloomfield\, G. G. Wallace\, I. Diez-Perez and M. L. Coote\, Natu
 re 2016 531\, 88-91\n3. (a) G. Gryn'ova\, D.L. Marshall\, S.J. Blanksby an
 d M. L. Coote Nature Chem. 2013\, 5\, 474-481. (b) G. Gryn'ova and M.L. Co
 ote J. Am. Chem. Soc. 2013\, 135\, 15392-15403. (c) M. Klinska\, L. M. Smi
 th\, G. Gryn’ova M. G. Banwell and M. L. Coote\, Chem. Sci. 2015\, 6\, 5
 623–5627.\n\n 
LOCATION:BCH 2201 https://plan.epfl.ch/?room==BCH%202201
STATUS:CONFIRMED
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