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

1. Paracyclophenylenes Carbon Nanohoop Structures • Gary Lloyd Lim • Miljanić Group Meeting / Literature • University of Houston ▪ Houston, TX ▪ January 16th2009

2. 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.

3. 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

4. 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.

5. 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.

6. It is possible to convert cyclohexadiene moiety to aryl ring Liu, H.-J.; Yip, J., Shia, K.-S. Tetrahedron Lett.1997, 38, 2253.

7. 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.

8. 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

9. 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

10. 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