Binding Energy and Mechanisms of Conjugated Enediynes with a Ruthenium complex

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Lynn Tai Prime 2008 Monash University- Melbourne,
Australia 14th August, 2008 Mentors Prof. Kim
Baldridge, Celine Amoreira
Binding Energy and Mechanisms of Conjugated
Enediynes with a Ruthenium complex
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Recently Discovered Organometallic Reaction

• Conjugated Enediyne
• Ruthenium Complex
• Aromatic Ring

1 Bonding site 4-yne and 4-ene 2 Bonding Sites
5-diyne and 5-enyne 3 Bonding Sites 6
Cannot be determined in the laboratory and
therefore computational chemistry must be applied!
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What is a Conjugated Enediyne?

• Enediynes are made up 9 to 10 carbon and hydrogen
  member rings that have two triple bonds and a
  double bond.
• They have a general delocalization due to the
  double and triple bonds.
• The enediyne group is very susceptible to
  cyclization forming aromatic rings.
• One type of reaction is the Bergman
  cycloaromatization reaction where the enediyne
  forms a benzene through a 1,4 benzenoid diradical
  intermediate.

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What is a ruthenium complex and a aromatic ring?

• The ruthenium complex is a metal coordination or
  metal complex in which a metal is surrounded by
  ligands.
• This is possible due to the metals ability to
  expand the number of electrons permitted in the
  outermost orbital.
• The ligands are usually bound to the metal
  through coordinate covalent bonds in which a pair
  of electrons are donated to the metal.
• An aromatic ring are organic compounds that are
  made up of planar rings that must be conjugated
  (there is a general delocalization due to
  alternating double and single covalent bonds or
  alternating pi bonds).

So the Enediyne reacts with the ruthenium complex
to form an aromatic ring which is a
organometallic compound!
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Background on Organometallics and their importance

• Organometallic compounds play a vital role in our
  day-to-day lives.
• Important in catalytic reactions that are used
  for the manufacture of commercially important
  materials.
• Organometallic complexes are also found in
  nature, a common example being methylcobalamine.
• The mechanism this project is based on is the
  metal-catalyzed Bergman cycloaromatization of
  enediynes.
• These organic metallic compounds can be used as
  DNA cleavage agents
• This mechanism may even be useful in terms of
  anti tumor activity.
• New reactions which involve the formation of
  metal-carbon bonds are therefore of great
  interest to scientists.

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Method
MOLECULAR STRUCTURE
CONTRL SCFTYPRHF RUNTYPOPTIMIZE COORDCART
END BASIS GBASISN311 NGAUSS6 NDFUNC2
NPFUNC1 END DFT METHODGRID DFTTYPBHHLYP
END SYSTEM MWORDS12 MEMDDI800 END STATPT
HSSEND.T. END DATA EneDiyne Cn 1 C
6.0 0.875845 1.962503 0.000000 C
6.0 -0.070443 1.223857 0.000000 C
6.0 -1.116586 0.432450 0.000000 C
6.0 -1.023213 -0.905244 0.000000 C
6.0 0.122733 -1.543640 0.000000 C
6.0 1.162462 -2.143659 0.000000 H
1.0 1.713700 2.611642 0.000000 H
1.0 -2.108990 0.913126 0.000000 H
1.0 -1.939215 -1.519130 0.000000 H
1.0 2.082375 -2.670102 0.000000
END
Determine Symmetry and Basis Set
GAMESS input file - Optimization
Nimrod Grid
GAMESS output file- Optimized Structure
Can Be Viewed on MacMolPlt
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Method Cont.
GAMESS output file- Optimized Structure
GAMESS input file - Energy
Nimrod Grid
Can Be Viewed on MacMolPlt
GAMESS output file- Energy Calculations
Analysed and most stable structure determined
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Alternative Method- Kepler
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Preliminary Results for Basis-Sets
with BHHLYP
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Preliminary Analysis
Electrostatic potential map of benzenediyne
Molecular orbital map of benzenediyne
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How to Proceed

• Continue Basis Set evaluation
• Determine most accurate levels of theory for run
• Perform Energy runs for molecules on GAMESS
• Ultimately determine which mechanism has the
  lowest energy structure

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Acknowledgements

• University of Zurich Mentor Dr. Kim K.
  Baldridge, Assistant Celine Amoreira
• UCSD Professor Dr. Joe OConnor
• Monash University Supervisors and Mentors David
  Abramson, Colin Enticott
• All made possible by PRIME! Peter Arzberger,
  Gabriele Wienhausen, Teri Simas
• Thank you!