ROSETTE NANOTUBES

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ROSETTE NANOTUBES

• Presentation by Adam Keller
• Based on the work of
• Hicham Fenniri
• Purdue University

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There is much interest in molecular structures
that can self-assemble. Their study may lead
to a better understanding of natures approach to
generating supramolecular architectures that
possess a predefined shape, size, topology,
stereochemistry, hierarchy, and shape.
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What is a Rosette?
It is an especially stable, hexameric, disk
shaped aggregate. The disks spontaneously stack
in solution to produce cylindrical structure. The
subunits were designed and synthesized to
possess a Watson-Crick donor-donor-acceptor
H-bond array of guanine and acceptor-acceptor-don
or of cytosine. Each subunit (six for each
rosette) also possesses a sidechain the
identity of which dictates the functionality of
the resulting Nanotube.
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Subunit
SUBUNIT STRUCTURE
The arrows indicate the DDA-AAD sites
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Pictorial of rosette
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The formation of a Rosette nanotube occurs
spontaneously in water (analogous to biological
conditions). They are the only reported
structure (synthetic) known to do so under these
conditions. The nucleotide-like subunits self
assemble into the rosette, followed by the self
assembly of the rosettes (stacking) into
nanotubes.
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Cartoon Representation of Stacked Rosettes
The chirality of the sidechain translates into
the assumed chirality of the resulting nanotube
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The resulting nanotubes have the following
properties -tube diameter of 4 nm
(calc) -140 rosettes per tube
(average) -tunable chirooptical
propertieswhich can be
controlled by the chirality of sidechain
BUT..Fenniri and co-workers discovered a HUGE
advantage These structures can lend towards the
control and reproducibility Of their
chirooptical properties.
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CROWN ETHERS AS SIDECHAINS!
Incorporating an achiral crown ether as a
sidechain, the resulting rosettes can stack with
a left handed twist OR a right handed twist,
depending on the chirality of the ligand that
binds into crown ether pocket. An excess of
L-alanine in solution will cause the rosettes to
stack with a left handed twist. An excess of
D-alanine will cause them to stack with a
right- handed twist.
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The tubes can also revert from left-handed to
right-handed twist, and vice versa, depending on
the chirality of the excess ligand in solution.
Chiral tubes
Chiral tubes
Racemic tubes
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HOW MAY THEY BE USEFUL?
This process may be viewed as a process by which
a predefined set of physical and chemical
properties is expressed at the macromolecular
level through stereospecific, programmable,
and potentially autocatalytic sequence of
supramolecular reactions
-Fenniri
Therefore, these structures may have applications
in adaptive chemistry, dynamic combinatorial
chemistry, materials sciences, and in
Chirotechnology. It is also notable that the
dimensions of these nanotubes are on the Same
order as many ion channels used in living cell
membranes (possible application in medicinal
technology)
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REFERENCES

• Fenniri, Hicham. JACS 2002, 124, 11064-11072
• Timmerman Reinhoudt. JACS 1999, 121, 7154-7155
• Zimmerman. JACS 1998, 120, 9092-9093

most of the information contained in this
presentation is from the work done by Hicham
Fenniri et.al. , from Purdue University
(Rosette Nanotubes).