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NIR SPECT1QSWDPY OF SYNTHETIC METALS: INTERCAIATED GRAPHITE

H.A. Resing, M. J. Moran*, Gerald Ray Miller, L. G. Banks,

C. F. Poranski, Jr. and D. C. Weber Naval Research Laboratory, Washington, D. C. 20375, and Dept. of Chemistry, The University of Maryland, College Park, MD 20742, USA

ABSTRACT N4R techniques have been used in graphite intercalation systems for chemical analysis and for determinations of structure, molecular dynamics, exchange kinetics, conductivity and electron concentration. Salient results will be presented. We have been most interested in understanding the reaction 3As5 + 2Cn

2C"F6 + AsF3

for which a single, extremely narrow 19F NMR line is observed when AsF 5 reacts with graphite. In contrast, when the reaction MN2 AsF 6 (in CH3N02 ) + Cn-.-', NM 2 T + CnASF6

(2)

is carried out, followed by addition of the stoichicmetric amount of AsF , separate spectra for the AsF6 (a broad doublet) and lor AsF (a sharp 1:2:1 triplet) are observed,

indicating that thesi two species do not exchange fluorine atoms, and suggesting that eq. (1) is not reversible. The AsF. triplet gives an order parameter for the molecular thrae fold axis with respect to the graphite c-axis. The carbon-13 spectrum for a fifth stage intercalate of HNO shows the 2:2:1 triplet expected if each kind of layer Is resolved. INTRDEUCION Non metallic materials of high electrical conductivity (about 2/3 that of copper) [1] have been produced by the action of certain classes of very reactive chemicals on a broad variety of polymeric materials. The search is for conducting materials with the favorable properties of polymers: flexibility, high strength-to-weight ratio, cheapness, and ease of fabrication. As part of this search we need analytical techniques to understand the chemistry involved, physical methods to determine the *Current Address:

Mat. Res.

Soc.

Dept. of Chemistry, West Chester State College, West Chester, PA

Symp. Proc. Vol.

20 (1983)

Published by Elsevier Science Publishing Co.,

Inc.

356

electronic structure of the solids, and even measurements of the electrical conductivity itself. In this note we describe how the Nuclear Magnetic Resonance (NMR) spectroscopy facilities at NRL have been used in this quest. A conductive polymer may be produced either by (a) the adding of electrons to its framework through the use of a "donor" dopant or (b) the withdrawal of electrons from the framework by an "acceptor" dopant/intercalant. The electron transfer is accompanied by the incorporation into the solid polymer body of part of the reagent which causes the transfer, and sometimes even by incorporation of neutral species as well; the process is called doping (in network polymers) or intercalation (in layered hosts such as graphite). The examples presented all deal with the sheet polymer graphite as befits this symposium. Our interest is in the acceptors because (a) their mode of action is still controversial, and (b) they appear at present to offer the best hope of chemically stable conducting materials. In what follows,