Transcript Nanostructural Architectures from Molecular Building Blocks

Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
 Molecular building blocks:
 MBBs are the link between classical
synthsis chemistry from in theory the
smallest possible unit, and large structures.
 MBBs are molecules that self assemble into
larger units.
 The limitations of this method are:
 Availability of the units, connectivity, and
suitable linkers
Nanostructural Architectures from
Molecular Building Blocks
 Bonding and connectivity
– Covalent bonding
– Covalent bonds are formed by the sharing of pairs of
electrons between atoms.
– Best example is the covalent bond between two C
atoms.
– Sigma bonding along the axis between the two atoms,
provides a means of low energy rotation in linear
molecules and low energy angle twisting in cyclic
molecules.
– Sigma bonding defines the general connectivity and
framework of the molecule
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
 Covalent bonding has many advantages:
– Covalent bonds lead to extremely stable
intermolecular connections, as compared to
electrostatic interactions (temperature, ionic
strength, pH)
– Covalnet bonds are dependable, they do not
reorganise, like hydrogen bonds
– Protocols exist to form all kinds of covalent
bonds for all kinds of building blocks, allowing
all possible connectivities
Nanostructural Architectures from
Molecular Building Blocks
 Coordination complexes
– In between the covalent bonds and the other
interamolecular interactions are the coordination
complexes between organic molecules and
metal ions.
– The initial description of these metal ligand
molecules stems from the ability of metal ions to
coordinate ligands electron donating molecules
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
 Dative bonds:
– Interaction of a lone pair with an atom centered
molecular orbital. Strength comparable to a
sigma bond.
– E.g. Bonding between B and N.
– Coupling of a molecule to B with a lone pair
leads to change in boron from trigonal planar
(sp2) to tetrahedral (sp3).
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Boroadamantane is a special case, because B is
already in sp3 hybridisation and has the final
conformation already built in the molecule.
Nanostructural Architectures from
Molecular Building Blocks
  Interactions
– They play a role in base stacking in DNA
– Molecular crystals
– Polymer chemistry
– Foramtion, shape and function of proteins
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
 Molecular building block approaches
– The ultimate goal is the assembly of nanostructures or
nanoscale materials through the manipulation of a
subunit by chemical modification
– The MBB is devisible into one or more
chemically/electrostaically active region
 Supramolecular Chemistry
 Science of electrostatic interaction at the
molecular level
Nanostructural Architectures from
Molecular Building Blocks
 Hydrogen bonding
 It is used extensively in Supramolecular
Chemistry
 Easy means to self assemble large units
from smaller subunits, can rearrange
 Stability increases with the total amount of
Hydrogen bonds
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
 Crystal Engineering
– Hydrogen Bonding has been extensively used
in the stabilisation of crystal lattices.
– Hydrogen bonding is one of the main bonding in
biological molecules
– Stabilisation of structures and backbones
– Secondary structure stabilisation
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
 Supramolecular structures
 Whole families of Supramolecular structures
are known that have been built up only by
Hydrogen bonding
 Mixing the units in te correct ratios will lead
to the self assembly of the desired
structures
 Cavities, sheets, triangular structures,…..
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
 Catenanes
– Catenanes are a very special class of
supramolecular molecules
– They come into existence when two
macrocycles interpenetrate each other.
– The first catenane has been synthesised in very
poor yields
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
 Molecular Zippers
– Molecular zippers are formed by amide oliomers
– They maximise the amount of Hydrogen
bonding and -stacking
– Stabiloity increases with oligomer length
– Decrease in stability in polar solvents
(methanol)
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
 Covalent Architectures
 The Tinkertoy chemist
 Idea behind the concept to build all possible
structures and shapes from a limited set of
molecules where all possible connectivities
of each single are known
 LEGO block system for organic chemistry
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
 Stability:
– Stability and reactivity are the most important
factors
– The MBBS should only react during the
formation of the structure and result in an inert
structure at the end of the reaction
 Size
– Control over the size is better the smaller the
single building blocks are.
Nanostructural Architectures from
Molecular Building Blocks
 Chemical reactivity
– From the box of the 24 molecules the reactivity
and reaction chemistry is known and described.
– Protocols for all possible linking reactions are
known
– Engineering all possible shapes is possible
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Honeycomb lattices
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
 Symmetry interaction model
– Symmetry interaction model builds on the
understanding that many highly symmetric
naturally occuring structures are formed as a
consequence of lock and key interactions
between the subunits.
– Metal complex chemistry uses these principles
to generate new metal-ligand assemblies
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
 2 Dimensional structures
 Virtually no limit in structural combinations
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
 3D structures
 Spotaneous self assembly from non
covalent self assembly is a known principle
in biological structures
 Proteins
 Ladders
 Rods
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks
Nanostructural Architectures from
Molecular Building Blocks