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Improvements to a Peak Assignment Algorithm for Two-Dimensional NMR Correlation Spectra of Zeolites Using Graph Theory

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Darren H. BROUWER^{a} and E. Keith LLOYD^{b}*

^{a}School of Chemistry, University of Southampton,
Southampton, United Kingdom, SO17 1BJ

^{b}School of Mathematics, University of Southampton,
Southampton, United Kingdom, SO17 1BJ

(Received: May 24, 2004; Accepted for publication: July 1, 2004; Published on Web: September 10, 2004)

An improved version of a peak assignment algorithm for two-dimensional NMR correlation spectra of zeolites is described. Both the zeolite framework structure and the two-dimensional NMR correlation spectrum can be expressed as graphs such that the task of peak assignment is to find labelings of the vertices of the graphs which show that the two graphs are homomorphic. In this paper, it is shown that an initial analysis of the structure and spectrum graphs provides information about the possible identities of the peaks which can lead to large gains in the efficiency of the peak assignment algorithm. The improvements in the algorithm are demonstrated for the peak assignment of solid state magic-angle spinning ^{29}Si NMR spectra of the purely siliceous zeolite ZSM-5 from two-dimensional ^{29}Si INADEQUATE NMR spectra.

**Keywords:** Nuclear magnetic resonance, Zeolites, Graph theory, Peak assignment

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