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Aggregation and Photodimerization of Areno‐Condensed Annulenes
Author(s) -
Schnorpfeil Christoph,
Meier Herbert,
Irie Masahiro
Publication year - 2001
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 - 10.1002/1522-2675(20010919)84:9<2467::aid-hlca2467>3.0.co;2-y
Subject(s) - chemistry , pyrene , excimer , phenanthrene , monomer , annulene , photochemistry , fluorescence , excited state , ring (chemistry) , emission spectrum , spectral line , computational chemistry , organic chemistry , polymer , physics , quantum mechanics , astronomy , nuclear physics
[18]‐ and [24]Annulenes condensed with three pyrene or phenanthrene ring systems show, in solution, especially in apolar solvents, a strong aggregation evidenced, for example, by concentration‐dependent 1 H‐NMR spectra. However, the fluorescence bands and the fluorescence lifetimes of these compounds depend only to a minor extent on the concentration and correspond essentially to the measurements obtained for the monomer. Among several models discussed, one is favored in which aggregates can be excited, but the emission is due to an almost undisturbed monomer. Even for the pyrene system, an excimer fluorescence cannot be detected. Nevertheless, short‐lived excimers are responsible for the regio‐ and stereoselective photodimerization to belt cyclophanes.