4th EucheMs chemistry congress

Monday, 27-Aug 2012
s834
chem. Listy 106, s587–s1425 (2012)
solid state Chemistry Materials chemistry/New materials
self-assembly, Molecular Recognition and Biomaterials – ii
o - 1 1 2
ChArGe-ASSiSted hydroGen BondS And weAK
interMoLeCuLAr interACtionS AS tooLS to
fABriCAte CoMPLex SuPrAMoLeCuLAr
ArChiteCtureS
A. CoMotti 1 , S. BrACCo 1 , M. BerettA 1 ,
M. d. wArd 2 , P. SozzAni 1
1 University of Milano Bicocca, Department of Materials Science,
Milano, Italy
2 New York University, Department of Chemistry, New York, USA
The rational design of synthetic supramolecular
architectures based on well-defined structure-directing forces and
hydrogen bonding is still a challenge. We present a
supramolecular cage assembled through 72 hydrogen bonds
which is constructed from two kinds of hexagonal molecular tiles
forming a truncated octahedron, one of the thirteen Archimedean
polyhedra (Science 2011, 333, 436). The framework displays an
extraordinary ability to encapsulate a wide range of differently
charged species, not observed otherwise.
By the exploitation of the same kind of interactions,
orientation of polyconjugated guest molecules is obtained in
tunable host cavities. The framework host architectures can be
controlled systematically in a manner that enables the regulation
of the guest orientation and aggregation (J. Am. Chem. Soc. 2010,
132, 14603). The effects of the distinct packing motifs is
manifested as bathochromic shifts in the absorption and emission
spectra of the guests as interpreted by ab initio TDDFT
calculations.
Interestingly, through CH···pi interactions, the molecular
recognition of specific blocks of triblock copolymers by a host
molecule promotes the formation of hierarchical periodic
structures. The formation of the supramolecular architectures is
followed by in situsynchrotron X-ray diffraction while the
specific CH···pi intermolecular interactions are highlighted by
fast-1H MAS NMR and GIAO HF ab initio calculations (J. Am.
Chem. Soc. 2011, 133, 8982).
Moreover, weak intermolecular interactions play a key role
in modulating the dynamics of molecular rotors in amphidynamic
materials. Indeed, the precise engineering of highly-organized
porous silica scaffolds supporting organic elements allows the
fabrication of fast molecular rotors (k>108 Hz) entirely exposed
to the guest molecules which act as regulators (Angew. Chemie
Int. Ed. 2010, 49, 1760).
Keywords: Crystal Engineering; Block Copolymers; Hydrogen
bonds; Materials science;
4 th EucheMs chemistry congress
self-assembly, Molecular Recognition and Biomaterials – iii
o - 1 1 3
dnA MAteriALS And nAnoMAChineS
n. SeeMAn 1
1 New York University, Department of Chemistry, New York, USA
We build branched DNA species that can be joined using
sticky ends to produce N-connected objects and lattices. We have
used ligation to construct DNA stick-polyhedra and topological
targets, such as Borromean rings. Branched junctions with up to
12 arms have been produced.
Nanorobotics is a key area of application. We have made
robust 2-state and 3-state sequence-dependent devices that change
states by varied hybridization topology. Bipedal walkers, both
clocked and autonomous have been built. We have constructed a
molecular assembly line by combining a DNA origami layer with
three 2-state devices, so that there are eight different states
represented by their arrangements. We have demonstrated that all
eight products (including the null product) can be built from this
system.
A central goal of DNA nanotechnology is the self-assembly
of periodic matter. We have constructed 2-dimensional DNA
arrays with designed patterns from many different motifs. We
have used DNA scaffolding to organize active DNA components.
Active DNA components include DNAzymes and DNA
nanomechanical devices; both are active when incorporated in 2D
DNA lattices. We have used pairs of 2-state devices to capture a
variety of different targets. Multi-tile DNA arrays have been used
to organize gold nanoparticles in specific arrangements.
We have self-assembled a 3D crystalline array and have
solved its crystal structure to 4 A resolution, using unbiased
crystallographic methods. More than ten other crystals have been
designed following the same principles of sticky-ended cohesion.
We can use crystals with two molecules in the crystallographic
repeat to control the color of the crystals. Thus, structural DNA
nanotechnology has fulfilled its initial goal of controlling the
structure of matter in three dimensions. A new era in nanoscale
control awaits us.
Acknowledgement: This research has been supported by the
NIGMS, NSF, ARO, ONR and the W.M. Keck Foundation.
Keywords: DNA Nanotechnology; Self-Assembled 3D Crystals;
Nanomechanical Devices; N-Connected Objects; Topological
Control;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc