Carbon-13 N.M.R. chemical shift and electronic structure of an infinite polymer chain as studied by tight-binding MO theory Polyethylene, and cis and trans polyacetylenes

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Abstract
A tight-binding MO theory has been used to derive a formalism for calculating the 13C N.M.R. chemical shift of an infinite polymer chain with the sum-over-state approximation. This formalism has been applied to the calculation of the 13C N.M.R. shielding tensor of polyethylene using the extended Hückel MO theory. In order to discuss the specification of the finite interaction length for the 13C N.M.R. chemical shift of any specified CH2 group of polyethylene chain, 13C N.M.R. chemical shifts of some n-paraffins with 1–16 carbon atoms are calculated in the sum-over-state approximation using the extended Hückel MO theory, and are compared with the experimental values. In addition the 13C N.M.R. chemical shifts of polyacetylenes with trans and cis forms are calculated using the above theory and the results are found to agree with the experimental data.