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Published on: May 8, 2015
Squaraine-derived rotaxanes: sterically protected fluorescent near-IR dyes
Easwaran Arunkumar1, Christopher C Forbes, Bruce C Noll
1Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA.
Abstract:
A squaraine dye with bulky end groups is employed as the thread component in two Leigh-type amide rotaxanes. The rotaxanes are synthesized in a simple two-step process. X-ray crystal structures of the rotaxanes show that the pyridyl-containing macrocycle is more rigid and wraps more tightly around the cyclobutene core of the squaraine thread compared to the isophthalamide-containing macrocycle. The rotaxanes exhibit photophysical properties that are similar to the precursor squaraine. The encapsulating macrocycle greatly increases the chemical stability of the squaraine thread and inhibits aggregation-induced broadening of its absorption spectrum. It should be possible to prepare squaraine-derived rotaxanes with improved properties for a wide range of photophysical, photochemical, and biomedical applications.
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