Search

Your search keyword '"Jennifer L Herek"' showing total 4 results
Start Over Author "Jennifer L Herek" Publisher american chemical society
4 results on '"Jennifer L Herek"'

1. Ultrafast carotenoid band shifts: Experiment and theory

Author

M. Wendling, G Garcia-Asua, C N Hunter, Tomáš Polívka, Villy Sundström, Richard J. Cogdell, Zhi He, Jennifer L. Herek, Tõnu Pullerits, R. Van Grondelle, and Biophysics Photosynthesis/Energy

Subjects
biology, Time-dependent density functional theory, biology.organism_classification, Purple bacteria, Surfaces, Coatings and Films, Light-harvesting complex, chemistry.chemical_compound, Dipole, chemistry, Chemical physics, Computational chemistry, Electric field, Materials Chemistry, Bacteriochlorophyll, Physical and Theoretical Chemistry, Local field, Excitation
Abstract

The ultrafast carotenoid band shift upon excitation of nearby bacteriochlorophyll molecules was studied in three different light harvesting complexes from purple bacteria. The results were analyzed in terms of changes in local electric field of the carotenoids. Time dependent density functional theory calculations based on known and model structures led to good agreement with experimental results, strongly suggesting that the mutual orientation of the pigment molecules rather than the type of the carotenoid molecules determines the extent of the ultrafast band shift. We further estimate that the protein induced local field nearby carotenoid molecule is about 4 or 6 MV/cm, depending on the orientation of the change of the electrical dipole in the carotenoid upon optical transition.

Published
2004
Full Text
View/download PDF

2. Tunable Aggregation and Luminescence of Bis(diarylethene)sexithiophenes.

Author

Maaike T. W. Milder, Jennifer L. Herek, Jetsuda Areephong, Ben L. Feringa, and Wesley R. Browne

Subjects
*CLUSTERING of particles, *LUMINESCENCE, *THIOPHENES, *FUNCTIONAL groups, *TEMPERATURE effect, *ABSORPTION spectra, *ELECTRONIC structure, *MOLECULE-molecule collisions, *SUPRAMOLECULAR chemistry
Abstract

Diarylethenes with two different side groups (phenyl and chloro) were appended to both α-ends of a sexithiophene unit. The temperature dependent aggregation properties for both compounds were characterized by steady state and transient absorption spectroscopy. The peripheral side groups show an unexpectedly significant influence on the electronic properties of the sexithiophene core. Furthermore, the relative influence of the phenyl and chloro substituents on the aggregation behavior observed is remarkable. The phenyl compound exhibits formation of H-aggregates over a narrow temperature range, between 240 and 200 K, typical of strong intermolecular interactions. In contrast, the chloro compound shows gradual aggregation over a wide temperature range, forming H-aggregates albeit with weaker intermolecular interactions. The results demonstrate that minor changes in the structure lead to tunability of the aggregation and corresponding luminescence properties of sexithiophenes in solution and hold particular relevance to supramolecular and polymer systems based on sexithiophene units. [ABSTRACT FROM AUTHOR]

Published
2009
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results