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Conjugative, Exciton and Charge‐Resonance Interactions in D 2 d ‐9,9′‐Spirobifluorene and D 2 d ‐Tetrabenzotricyclo [5.5.0.0 2,8 ]dodeca‐3,5,9,11‐tetraene. Photoelectron and Polarized Absorption Spectra
Author(s) -
SpangetLarsen Jens,
Gleiter Rolf,
Haider Rudolf
Publication year - 1983
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19830660513
Subject(s) - chemistry , exciton , absorption spectroscopy , resonance (particle physics) , homo/lumo , valence (chemistry) , molecular electronic transition , chromophore , fluorene , spectroscopy , spectral line , vibronic coupling , atomic physics , photochemistry , polymer , molecule , physics , condensed matter physics , organic chemistry , quantum mechanics , astronomy
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.