ISMSC 2007 - Università degli Studi di Pavia

Macrocyclic hosts for supramolecular and traditional coordination
chemistry
Kristin Bowman-James
Department of Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, Kansas
66045 USA
Interactions linking hosts with their guests in chemistry and biology range from simple to
complex. They include supramolecular “coordination chemistry” involving hydrogen bonding
networks as well as traditional coordination chemistry involving coordinate covalent bonds with
transition metal ions. In order to understand the basic topological concepts regulating anion
recognition (anion coordination chemistry), we designed a series of macrocycles based on
simple amide/amine frameworks and used a systematic approach to examine the influence of
increasing complexity or dimensionality. Since anions and transition metal ions often bind
similar types of functional groups, i.e., protonated amines and amides for the former and neutral
amines and deprotonated amides in the latter, we have also begun exploring our anion hosts as
ligands for transition metals ions. Structural and chemical findings for monoatomic (F – , H + , M 2+ ,
M 3+ ), linear (FHF – , N3 – ), and other multiatomic (HSO4 – , ReO4 – , P2O7 2– , Cr2O7 2– ) complexes,
among others, will be described.
N N
N N N
Bicycles
N N
= ,
N
, O
N = amine linker
N
N
N N N N
Tricycles
N
N
PL 3
Covalent and Coordinative Dynamic Chemistry
J Fraser Stoddart
California NanoSystems Institute and Department of Chemistry & Biochemistry, University of
California, Los Angeles, 607 Charles E Young Drive East, Los Angeles, CA, USA 90095-1569
The chemical synthesis of (functional) materials is in a state of rapid development and
considerable flux these days. The profound influence that supramolecular chemistry has had
on the development of chemical science during the past few decades has led, in the first
instance, to supramolecular assistance to covalent synthesis, and then subsequently to
dynamic coordinative and covalent synthesis. Templation is central to success whichever
variant of the synthetic protocols is being employed.
For the synthesis of a particular molecular compound or specific extended structure to proceed
with efficiency, reactions under thermodynamic control have to be associated with the
overwhelming preference for one compound or structure over all the other possibilities, i.e., lock
and key chemistry. When kinetic control is operating, reactions which proceed apace and go to
completion, are very attractive candidates for synthesis, i.e., click chemistry. Phase changes
can also be used in an extremely effective manner to capture a product in a kinetic fashion from
an equilibrium mixture of products, e.g., crystallization of one of the less stable compounds from
a dynamic combinatorial library.
A Collage of Form and Function
PL 4
The lecture will focus, by way of examples, on the reversible nature of imine bond formation,
imine exchange, olefin metathesis in the presence of (Grubbs) catalysts, and the Menschutkin
reaction, as well as the irreversible copper-catalyzed Huisgen dipolar 1,3-cycloaddition between
an alkyne and an azide, all happening in some context or other where templation through metal
coordination, donor-acceptor interactions and/or hydrogen bonding is operative. The products
will all be mechanically interlocked compounds, including (bistable) catenanes and (bistable)
rotaxanes, Borromean rings, Solomon links, and molecular bundles and switches. Functions,
that will be addressed, will include nanovalves and molecular memory.
[1] “Molecular Borromean rings,” Science 2004, 304, 1308–1312.
[2] “A molecular Solomon link,” Angew. Chem., Int. Ed. 2006, 46, 218–222.
[3] “Efficient templated synthesis of donor-acceptor rotaxanes using click chemistry,” J. Am.
Chem. Soc. 2006, 128, 10388–10390.
[4] “A 160-kilobit molecular electronic memory patterned at 10 11 bits per square centimetre,”
Nature 2007, 445, 414–417.