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At least 289 records · Page 16Linked to original sources
PubMed2004

Influence of chain length on exciton migration to low-energy sites in single fluorene copolymers.

Fluorescence spectroscopy was performed on single molecules of two 9,9-dialkylfluorene-benzothiadazole (FxBT) copolymers with a 10-fold difference in average molecular weight. Molecules of both polymers exhibit red-shifted emission indicative of energy migration to low-energy sites (LES) on the polymer chains; however, "red" spectra are much more common for the longer polymer. Since singlet-exciton migration is found to occur on the molecular length scale in both cases, the increased number of red-shifted spectra observed for the longer polymer is evidence that the likelihood of LES formation increases with chain length. This relationship is discussed in terms of three possible causes of low-energy sites: local polymer conformations, chromophores with extended conjugation lengths, and random chemical defects.

Energy Transfer↗
PubMed2001

1,4-Methano-11a-methyl-4,4a,11,11a-tetrahydro-1H-benzo[b]fluoren-11-one.

The title compound, C(19)H(16)O, crystallizes with two molecules of opposite chirality in the asymmetric unit. In both molecules, the naphthalene and cyclopentanone moieties are individually planar. The two cyclopentane rings adopt envelope conformations, while the cyclohexane ring adopts a boat conformation.

Coumarins↗
PubMed1998

9H-fluorene-2-carboxaldehyde.

The title compound, C14H10O, crystallized in the centrosymmetric space group P2(1)/c with a single molecule in the asymmetric unit. The C-H...O interaction having the shortest C...O distance involves the ring-bridging C9 atom and one of its H atoms, and results in the formation of a cyclic dimer about a center of symmetry. The molecular core is nearly planar. The dihedral angle between the best-fit plane of the ring to which the aldehyde group is attached and the plane of the aldehyde group is 4.4 (9) degrees. In a number of respects the molecular disposition is similar to that previously determined for the geometrically similar dibenzofuran-4-carboxaldehyde molecule.

Aldehydes↗