| Autor: |
Matikonda SS; Chemical Biology Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 376 Boyles Street, Frederick, Maryland 21702, United States., Hammersley G; Chemical Biology Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 376 Boyles Street, Frederick, Maryland 21702, United States., Kumari N; School of Molecular Sciences and The Biodesign Institute at Arizona State University, Tempe, Arizona 85287, United States., Grabenhorst L; Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, München, 81377, Germany., Glembockyte V; Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, München, 81377, Germany., Tinnefeld P; Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, München, 81377, Germany., Ivanic J; Advanced Biomedical Computational Science, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702, United States., Levitus M; School of Molecular Sciences and The Biodesign Institute at Arizona State University, Tempe, Arizona 85287, United States., Schnermann MJ; Chemical Biology Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 376 Boyles Street, Frederick, Maryland 21702, United States. |
| Abstrakt: |
Appending conformationally restraining ring systems to the cyanine chromophore creates exceptionally bright fluorophores in the visible range. Here, we report the application of this strategy in the near-infrared range through the preparation of the first restrained heptamethine indocyanine. Time-resolved absorption spectroscopy and fluorescence correlation spectroscopy verify that, unlike the corresponding parent unrestrained variant, the restrained molecule is not subject to photoisomerization. Notably, however, the room-temperature emission efficiency and the fluorescence lifetime of the restrained cyanine are not extended relative to the parent cyanine, even in viscous solvents. Thus, in contrast to prior reports, the photoisomerization of heptamethine cyanines does not contribute significantly to the excited-state chemistry of these molecules. We also find that the fluorescence lifetime of the restrained heptamethine cyanine is temperature-insensitive and significantly extended at moderately elevated temperatures relative to the parent cyanine. Finally, computational studies have been used to evaluate the impact of the conformational restraint on atomic and orbital structure across the cyanine series. These studies clarify the role of photoisomerization in the heptamethine cyanine scaffold and demonstrate the dramatic effect of restraint on the temperature sensitivity of these dyes. |
