A graph-theoretical formula for computation of products of eigen coefficientsCrjCsj(r≠s) of a graph has been derived. A general formula for the characteristic polynomial of a linear chain having a branch with a weighted pendant vertex has been given. These have been utilised, together with the Ulam subgraph method for obtaining squares of eigen coefficients, to take into account the perturbations in Coulomb and resonance integrals due to introduction of heteroatoms in a conjugated system or due to attachment of Me groups to conjugated atoms. Heteroatom Hückel parametersh andk of N and Me groups have been estimated and some structural information about a number of electron donors have been extracted by applying the results to the trends in the charge-transfer bands of their π-type molecular complexes.
Volume 134, 2022
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