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

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 29Si NMR spectra of the purely siliceous zeolite ZSM-5 from two-dimensional 29Si INADEQUATE NMR spectra.