Self-Assembly of Fluorescent Inclusion Complexes in Competitive Media Including the Interior of Living Cells

Jeremiah J. Gassensmith, Easwaran Arunkumar, Lorna Barr, Jeffrey M. Baumes, Kristy M. DiVittorio, James R. Johnson, Bruce C. Noll, and Bradley D. Smith*
Contribution from the Department of Chemistry and Biochemistry and the Walther Cancer Research Center, University of Notre Dame, Notre Dame, Indiana 46556
J. Am. Chem. Soc., 2007, 129 (48), pp 15054–15059
DOI: 10.1021/ja075567v
Publication Date (Web): November 10, 2007
Copyright © 2007 American Chemical Society
*

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

, smith.115@nd.edu

Abstract

Abstract Image

Anthracene-containing tetralactam macrocycles are prepared and found to have an extremely high affinity for squaraine dyes in chloroform (log Ka = 5.2). Simply mixing the two components produces highly fluorescent, near-infrared inclusion complexes in quantitative yield. An X-ray crystal structure shows the expected hydrogen bonding between the squaraine oxygens and the macrocycle amide NH residues, and a high degree of cofacial aromatic stacking. The kinetics and thermodynamics of the assembly process are very sensitive to small structural changes in the binding partners. For example, a macrocycle containing two isophthalamide units associates with the squaraine dye in chloroform 400 000 times faster than an analogous macrocycle containing two 2,6-dicarboxamidopyridine units. Squaraine encapsulation also occurs in highly competitive media such as mixed aqueous/organic solutions, vesicle membranes, and the organelles within living cells. The highly fluorescent inclusion complexes possess emergent properties; that is, as compared to the building blocks, the complexes have improved chemical stabilities, red-shifted absorption/emission maxima, and different cell localization propensities. These are useful properties for new classes of near-infrared fluorescent imaging probes.

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History

  • Published In Issue December 05, 2007
  • Received July 25, 2007

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