A New Class of Hydroxy-Substituted Squaraine Rotaxane

Na Fu; Jeremiah J. Gassensmith; Bradley D. Smith

doi:10.1071/CH09671

RESEARCH FRONT

Previous Next Contents Vol 63(5)

A New Class of Hydroxy-Substituted Squaraine Rotaxane

Na Fu ^A , Jeremiah J. Gassensmith ^A and Bradley D. Smith ^A ^B

+ Author Affiliations

- Author Affiliations

^A Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46545, USA.

^B Corresponding author. Email: smith.115@nd.edu

Australian Journal of Chemistry 63(5) 792-796 https://doi.org/10.1071/CH09671
Submitted: 23 December 2009 Accepted: 10 February 2010 Published: 21 May 2010

Abstract

A templated macrocyclization reaction was used to permanently encapsulate a highly fluorescent hydroxy-substituted squaraine dye inside a tetralactam macrocycle. The free squaraine dye is quite rigid due to internal hydrogen bonding and its photophysical properties hardly change upon encapsulation. A combination of X-ray and NMR data show that the surrounding tetralactam macrocycle adopts an unusually rigid chair conformation and does not undergo rapid pirouetting. Because of its large size and conformational rigidity, the macrocycle creates anisotropic NMR shielding zones that extend over the N,N-dibutylamino groups at each end of the squaraine thread. This shielding anisotropy allows hindered aryl-N rotation to be observed by NMR spectroscopy and provides direct experimental evidence that quinoid-like resonance structures are major contributors to the bis(N,N-dialkylaminophenyl)squaraine resonance hybrid.

Acknowledgements

This work was supported by the NIH (USA).

References

A New Class of Hydroxy-Substituted Squaraine Rotaxane

Abstract

Acknowledgements

Subscriber Login