Perturbation theory of nonbonding orbitals in polymeric dyes

In terms of the approximation of an extremely long polymethine chain a relation was obtained between the electron-donating power φ0 and the effective length L of the terminal groups in cyanine dyes, on the one hand, and the form of their asymptotic nonbonding orbital, on the other. A simple general procedure for determining the coefficients of such orbitals is indicated. Expressions were obtained through these coefficients for the derivatives of φ0 and L with respect to the elements of the topological Hamiltonian of the terminal group, and this makes it possible to assess the effect of structural perturbations of the terminal groups on φ0 and L. The possibility of refinement of the absorption region of the dyes with a short polymethine chain is considered