C. Spitz et S. Daehne, ARCHITECTURE OF J-AGGREGATES STUDIED BY PRESSURE-DEPENDENT ABSORPTIONAND FLUORESCENCE MEASUREMENTS, Berichte der Bunsengesellschaft fur Physikalische Chemie, 102(5), 1998, pp. 738-744
Citations number
35
Categorie Soggetti
Chemistry Physical
Journal title
Berichte der Bunsengesellschaft fur Physikalische Chemie
The spectral shift of absorption and fluorescence bands as well as the
fluorescence decay of four J-aggregate forming 5,5',6,6'-tetrachlorob
enzimidacarbocyanine dyes have been investigated in solution under hig
h pressure up to 50 kbar. The investigated dyes differ only in their 1
,1' and 3,3' nitrogen substituents which do not influence the chromoph
ore itself. Whereas the spectral behaviour of the monomeric dyes is co
mparable to that of aromatic and polyenic compounds, the J-aggregates
show some unusual spectral features. Two types of J-aggregates can be
distinguished. One type exhibits a linear dependence of the absorption
and fluorescence maximum on pressure with vanishing Stokes shift over
the whole pressure range. The second type is characterised by a limit
ed shift of the absorption band to longer wavelengths whereas the Stok
es shift increases even at pressures where the absorption energy remai
ns constant. The spectral behaviour of the first type is consistent wi
th the well-known chain-shaped or brickstone-like structure of J-aggre
gates. As one dye of the second type is known to form optically active
, Davydov-split J-aggregates the pressure-dependent spectral behaviour
of such dyes corroborates the assumption that their J-aggregates cons
ist of helical cylindrical micelles.