Conjugative, Exciton and Charge-Resonance Interactions in D2d-9,9′-Spirobifluorene and D2d-Tetrabenzotricyclo [5.5.0.02,8]dodeca-3,5,9,11-tetraene. Photoelectron and Polarized Absorption Spectra

✍ Scribed by Jens Spanget-Larsen; Rolf Gleiter; Rudolf Haider

• Publisher: John Wiley and Sons
• Year: 1983
• Tongue: German
• Weight: 787 KB
• Volume: 66
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19830660513

✦ Synopsis

Abstract

Photoelectron spectroscopy, polarized electronic absorption spectroscopy in stretched polymer sheets, and semiempirical theoretical methods have been applied to investigate the valence electronic structures of the two title compounds 1 and 2, considering fluorene (3) as a reference compound. The results are analyzed in terms of ‘through space’ and ‘through bond’ conjugative effects and exciton and charge‐resonance interactions. Spiro‐conjugation in 1 is found to play a similar role as ‘through bond’ interaction via the cyclobutane ring in 2. In contrast to the results of a recent investigation, exciton coupling is found to be relatively insignificant, while charge‐resonance effects are important. The transition close to 41 000 cm^−1^ in the absorption spectra of 1 and 2 has no obvious counterpart in the spectrum of 3; it is assigned to a ^1^E^−^ state with large charge‐resonance character, involving promotion of an electron from the HOMO of one half‐chromophore to the LUMO of the other.