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Vibrational spectroscopy of C60 photopolymer

Funding: OTKA T034198,

OTKA T032613,

NATO PST.CLG.977404

G. Klupp*, K. Kamarás, É. Kováts, S. Pekker, T. Pusztai

Research Institute for Solid State Physics and Optics,P. O. Box 49, Budapest, H 1525, Hungary, *email: klupp@szfki.hu

Z.-T. Zhu†, V. C. Long‡, J. L. Musfeldt§

Department of Chemistry, State University of New York at Binghamton, Binghamton, New York 13902

G. B. Adams, J. B. Page

Department of Physics and Astronomy, Arizona State University, Tempe, Arizona 85287

Introduction

Monomer

+

Dimer

+

Trimers

(5 possible structures)

+

Tetramers

(17 possible structures)

+

Higher oligomers

(insolubes)

Photopolymer =

[1], [2], [3]

…

a = 13.93 – 14.05 Å average ~2 cycloadditional bonds / C60 unit [2], [4]

Different preparation conditions different ratio of the compounds [3], [5]

Measured Ag(2) modes

Preparation

Calculations

Measurements

- Illumination of C60 + saturated C60 solution with 2*23W at 320-360K for 40 days
C60 + (C60)2 + soluble (C60)n>2 + insoluble (C60)n>2

- Repeated extraction with toluene
solid photopolymer with less C60, (C60)2

solution of C60 + (C60)2

- HPLC separation of the solution
(C60)2, 99.3% purity

- For the preparation of trimer see poster of É. Kováts

- Method:
- QMD (quantum molecular dynamics) [6]
- local pseudoatomic orbitals, minimal basis
- best results: 200-600 cm-1 (FarIR): with 1.05 uniform scaling 2% error
- intensities not reliable
- Molecules:
- triangle: most possible (C60)3
- rectangle: most possible (C60)4

- Raman: Renishaw System 1000B microscope
- + 785nm laser further polymerization avoided
- MIR: KBr pellet in Bruker IFS28
- FIR: pure photopolymer pellet @ LHe (4 K) in Bruker IFS 113v
- Weak lines seensharper lines

5 cm-1/ cycloadditional bond

Photopolymer contains: C60 + (C60)2 + (C60)3 + higher oligomers

Measured and calculated MidIR spectra

Measured and calculated FarIR spectra

calc. rectangle

calc. triangle

exp. photopolymer

exp. dimer

Photopolymer contains dimer, but other oligomers are present

MidIR: assignment of oligomer peaks not conclusive FarIR: fewer lines + no C60 lines

No interball modes 30-200 cm-1

Assignment of photopolymer spectrum with dimer, triangle and rectangle

Unassigned peaks: insoluble oligomers + small amount of other trimers and tetramers

Conclusions

- Ag(2): 5 cm-1/ cycloadditional bond
- No interball modes in IR 30-200 cm-1
- FarIR more informative for assignment than MidIR
- Photopolymer contains monomer + dimer + triangle + rectangle + other oligomers

References

[1] A. M. Rao, P. Zhou, K-A. Wang, G. T. Hager, J. M. Holden, Y. Wang, W-T. Lee, X-X. Bi, P. C. Eklund, D. S. Cornett, M. A. Duncan, I. J. Amster, Science 259, 955 (1993)

[2] T. Pusztai, G. Oszlányi, G. Faigel, K. Kamarás, L. Gránásy, S. Pekker, Solid State Commun. 111, 595 (1999)

[3] S. Pekker, K. Kamarás, É. Kováts, T. Pusztai, G. Oszlányi, Synthetic Metals 121, 1109 (2001)

[4] S. Pekker, É. Kováts, K. Kamarás, T. Pusztai, G. Oszlányi, Synthetic Metals 133-134, 685 (2001)

[5] B. Burger, J. Winter, H. Kuzmany, Z. Phys B 101, 227 (1996)

[6] O. F. Sankey, D. J. Niklewski, Phys. Rev. B 40, 3979 (1989)

Present addresses:

† Department of Material Science and Engineering, Cornell University, Ithaca, NY 14853

‡ Department of Physics and Astronomy, Colby College, Waterville, ME 04901

§ Department of Chemistry, University of Tennessee, Knoxville, TN 37996