Title
Electronic states of anthanthrene : linear and magnetic circular dichroism, polarized fluorescence, and quantum chemical calculations Electronic states of anthanthrene : linear and magnetic circular dichroism, polarized fluorescence, and quantum chemical calculations
Author
Faculty/Department
Faculty of Sciences. Chemistry
Publication type
article
Publication
,
Subject
Chemistry
Source (journal)
Polycyclic aromatic compounds. - Place of publication unknown
Volume/pages
25(2005) :1 , p. 23-45
ISSN
1040-6638
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Abstract
The pericondensed benzenoid hydrocarbon anthanthrene (dibenzo[def,mno{]chrysene, dibenzo[}cd,jk{]pyrene) was investigated by UV-VIS and IR linear dichroism (LD) spectroscopy in stretched polyethylene, by UV-VIS magnetic circular dichroism (MCD) spectroscopy, and by fluorescence polarization anisotropy measurements. The combined results led to a detailed experimental characterization of electronic transitions in the near-UV and visible regions, with determination of polarization directions. In particular, the results allowed an unambiguous assignment of the weak L} b { transition (corresponding to Clar's }α {-band), in spite of overlap with the much stronger L} a { transition (Clar's} p{-band). This assignment, which is at variance with a previous suggestion, was supported by a study of solvent and temperature shifts. The experimental results were compared with theoretical predictions using the LCOAO procedure. Excellent agreement with observed transitions was obtained, including transition moment directions and MCD signs. The theoretical analysis revealed a significant breakdown of the alternant pairing symmetry for anthanthrene, corresponding to Δ HOMO > Δ LUMO. Similar to benzo[}a{]pyrene, anthanthrene can be classified as a positive-hard MCD chromophore in Michl's terminology.