Conjugated Compounds. III. Spectra and Ionization in Polyenes and Polymethines by a Finite Difference Method

Abstract

Periodic potential energies were calculated for x-electrons along the molecular axes of butadiene and three polymethines NH₂-(CH=CH)_n-CH= NH₂+, using Z'C = 1.0 and Z'N = 2.0 or 1 5 as the respective effective nuclear charges of the carbon and nitrogen nuclei. The Schroedinger equation was solved by finite differences, and with two restricted and self-consistent parameters, good agreement was obtained with observed ionization energies, band frequencies, and band intensities. The Brillouin zone effect is discussed, and also the screening in conjugated compounds. The use of an iteration procedure for the solution of eigenvalue problems by finite differences is described in Appendix I.