Paracyclophenylenes
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Miljanić Group Meeting / Literature University of Houston ▪ Houston, TX ▪ January 16 th 2009 PowerPoint PPT Presentation


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Paracyclophenylenes Carbon Nanohoop Structures. Gary Lloyd Lim. Miljanić Group Meeting / Literature University of Houston ▪ Houston, TX ▪ January 16 th 2009. Great Minds behind the Research. Carolyn Bertozzi PhD—University of California, Berkeley (1993)

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Miljanić Group Meeting / Literature University of Houston ▪ Houston, TX ▪ January 16 th 2009

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Miljani group meeting literature university of houston houston tx january 16 th 2009

Paracyclophenylenes

Carbon Nanohoop Structures

  • Gary Lloyd Lim

  • Miljanić Group Meeting / Literature

  • University of Houston ▪ Houston, TX ▪ January 16th2009


Miljani group meeting literature university of houston houston tx january 16 th 2009

Great Minds behind the Research

Carolyn Bertozzi

PhD—University of California, Berkeley (1993)

Predoc—Office of Naval Research (1988–1991)

Diploma—Harvard University (1988)

Professor at University of California, Berkeley

Jeffrey Neaton

Postdoc—Rutgers University, Physics (2000–2003)

The Molecular Foundry, LBNL (2003–2005)

PhD (Physics)—Cornell University (2000)

Diploma—University of Minnesota (1995)

Facility Director—Theory of Nanostructured Materials Facility

JoydeepBhattacharjee—NCN Postdoc

RameshJasti—University of California, Berkeley

Jasti, R.; Bhattacharjee, J.; Neaton, J.; Bertozzi, C. J. Am. Chem. Soc.2008, 130, 17646.


Miljani group meeting literature university of houston houston tx january 16 th 2009

California and Its Diversity

  • Located on West Coast of the US

  • 3rdlargest state (163, 696 sq. mi.)

  • Capital city is Sacramento

  • Most populous state (36,756,666)

  • Gross State Product of $1.812 trillion (2007)

  • Climate varies from Mediterranean to subartic

  • Well-known Universities in California:

    • University of California (10 campuses)

    • California Institute of Technology

    • Stanford University


Miljani group meeting literature university of houston houston tx january 16 th 2009

CycloparaphenyleneIs a Synthetic Challenge

strained and distorted

aromatic systems

radially oriented p-orbitals

3,6-syn-dimethoxy-cyclohexa-1,4-diene

provides the curvature and rigidity

necessary for macrocyclization

Parekh, V. C.; Guha, P. C. J. Indian Chem. Soc.1934, 11, 95.

Jagedeesh, M. N.; Makuy, A.; Chandrasekhar, J. J. Mol. Model.2000, 6, 226.


Miljani group meeting literature university of houston houston tx january 16 th 2009

Macrocylic precursors were prepared

34%

Alonso, F.; Yus, M. Tetrahedron1991, 47, 7471.

Song, Z. Z.; Wong, H. N. C. J. Org. Chem.1994, 59, 33.


Miljani group meeting literature university of houston houston tx january 16 th 2009

It is possible to convert cyclohexadiene moiety to aryl ring

Liu, H.-J.; Yip, J., Shia, K.-S. Tetrahedron Lett.1997, 38, 2253.


Miljani group meeting literature university of houston houston tx january 16 th 2009

What are the Properties of the Cycloparaphenylenes?

  • UV-Vis Absorption Spectra:lmax≈ 340 nm

  • Fluorescence Spectra:as carbon nanohoop size decreases,

    • the Stokes shift increases

Nijegorodov, N. I.; Downey, W. S.; Danailov, M. B. Spectrochim. Acta, Part A2000, 56, 783.


Miljani group meeting literature university of houston houston tx january 16 th 2009

Rings Are in a Staggered Configuration

Even-memberednanohoops, [12]- and [18] cycloparaphenylenes,

have dihedral angles of 33o and 34o between two adjacent phenyl rings

Strain energies of 28 and 5 kcal mol−1with diameters of 1.7 and 2.4 nm, respectively

Odd-memberednanohoop, [9] cycloparaphenylene,

has varying dihedral angles of 18o, 30o, 31o and 34o around the carbon nanohoop

Strain energy of 47 kcal mol−1 with a diameter of 1.2 nm


Miljani group meeting literature university of houston houston tx january 16 th 2009

Understanding its properties using Density Functional Theory

Eg = IP – EA – Ee-h

IP = ionization potential

EA = electron affinity

Ee-h = electron-hole interaction energy

  • IP – EA decreases as the number of phenyl rings increase

  • Ee-h grows dramatically with the decreasing number of phenyl rings

Large Stokes shift observed is governed by the degree of structural relaxation in the optically excited state

Enhanced curvature leads to greater sp3 hybridization and increasingly asymmetric p-orbital


Miljani group meeting literature university of houston houston tx january 16 th 2009

Cycloparaphenylenes Are Remarkable

  • 1) Cycloparaphenylenescan be synthesized using a masked aromatic ring moiety

  • 2) Cycloparaphenylenesare subunits of an armchair carbon nanotube

  • 3) Possible route to extended carbon nanotubes using solution-phase chemistry

  • 4) Preparation of carbon nanotubes of a specific chirality


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