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Experimental and computational probes of the space in a self-assembled capsule

Academic Article
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Overview

authors

  • Ajami, Dariush
  • Iwasawa, T.
  • Rebek Jr., Julius

publication date

  • 2006

journal

  • Proceedings of the National Academy of Sciences of the United States of America  Journal

abstract

  • Self-assembled capsules are hosts that recognize and surround smaller molecule guests of appropriate size, shape, and chemical surfaces. The space available inside is a cage of fixed solvent molecules, many of which are aromatic. These aromatics provide anisotropic shielding to guests, and a map of induced magnetic shielding for the inner space can be obtained through nucleus-independent chemical shift calculations. Experimental values of the magnetic environment can be determined by NMR spectra of the guests inside. We describe here the environment in a cylindrical capsule with tapered ends. A series of terminal acetylenes -- the narrowest of organic structures -- was synthesized and used to probe the magnetic shielding of the capsule's ends. Their NMR spectra showed that the acetylenic hydrogen experiences deshielding as it is forced deeper into the tapered end of the capsule where four benzene rings converge. Modeling and density functional theory calculations provided excellent agreement with the experimental values and established a molecular ruler to explore steric and magnetic environments inside the capsule.

subject areas

  • Acetylene
  • Calixarenes
  • Hydrogen
  • Hydrogen Bonding
  • Magnetic Resonance Spectroscopy
  • Molecular Conformation
  • Molecular Structure
  • Phenylalanine
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Research

keywords

  • encapsulation
  • nanochemistry
  • self-assembly
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Identity

PubMed Central ID

  • PMC1482543

International Standard Serial Number (ISSN)

  • 0027-8424

Digital Object Identifier (DOI)

  • 10.1073/pnas.0602781103

PubMed ID

  • 16751271
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Additional Document Info

start page

  • 8934

end page

  • 8936

volume

  • 103

issue

  • 24

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