Cyclodextrins and their Complexes

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Cyclodextrins and their Complexes
Molecules with holes...
Stoddart Cyclodextrins are all-purpose
molecular containers for organic, inorganic,
organometallic, and metalloorganic compounds that
may be neutral, cationic, anionic, or even
radical.
a
ß
glucopyranoside units
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EASY name to remember...
5,10,15,20,25,30,35- heptakis-(hydroxymethyl)-2,4,
7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaocta
cyclo 31.2.2.2.3,6.28, 11.213, 16.218, 21.223,
26.228,31nonatetracontane-36,37,38,39,40,41,42,43
,44,45,46,47,48,49-tetradecol
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In most cases these host molecules have an
average structure of a truncated cone with a
cavity lined with H3 and H5 protons and lone
pairs of glycosidic oxygen atoms lying in a plane
thus endowing the cavity with hydrophobic
character, while the bases formed by the primary
and secondary OH groups bestow a hydrophilic
character
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The great significance of CDs both in research
and applications lies in their ability to
selectively form inclusion complexes with other
molecules, ions, or even radicals. This
phenomenon bears the name molecular recognition
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By appropriate choice of host and guest one can
achieve a very high selectivity. 6 is complexed
much more strongly by the dimeric host 7 than is
8.
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Amazing sensitivity of CDs to the shapes of guest
molecules or ions
Most probably due to a difference in the
stoichiometry of these complexes. Namely, the
latter complexes are of 11 stoichiometry while
in the former one guest molecule is mostly
embedded in a capsule formed by two host CDs.
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flip-flop mechanism
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Molecular necklace
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Chemosensors Using Modified Cyclodextrins
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Numerous dye-modified CyDs were prepared as
chemosensors for highly selective and sensitive
molecular recognition
49 showed sensitivity for analytes such as
steroids and terpenes with different selectivity
from the native CD. 50 did not show any change
in fluorescence intensity upon the addition of
guests because of the strong inclusion of the
dansyl group into the CD cavity
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In the absence of guests effective quenching
occurred between included nitrobenzene and
pyrene, both closely located in the CD cavity.
The fluorescence intensity dramatically increases
with increasing concentration of a guest (e.g.
lithocholic acid), because the nitrobenzene
moiety is excluded from the CD cavity.
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Cyclodextrins Conjugated with Other Kinds of Hosts
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Metallocavitands Using Modified Cyclodextrins
Metallocavitands are expected to lead to the
development of new metal catalysts with enhanced
selectivities and activities, in particular
because of the protection against undesired side
reactions provided by substrate inclusion into
the CD cavity and by stabilization of unusual
coordination modes.
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Polymer Formation by Intermolecular Interactions
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Regulation of Photoreactions
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HostGuest Interactions
The intermolecular cavity of CDs includes H2O
molecules which are surrounded by a hydrophobic
wall mainly composed of hydrogen atoms.
Therefore, these H2O molecules cannot fully form
hydrogen bonds and are energetically less stable
than bulk water molecules. When a guest molecule,
of suitable size and preferably hydrophobic
character, is added to a CD solution, H2O
molecules in the CD cavity are replaced by the
guest molecule..
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Microcalorimetry
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Pharmaceutical Applications of Cyclodextrins and
Their Derivatives
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