13
Large Semiconductor Molecules
J. F. Corrigan and M. W. DeGroot
13.1
Introduction
The synthesis of large, discrete molecular complexes with several dozen, or indeed
several hundred, heavy atoms is currently the focus of numerous research efforts
worldwide and recent successful synthetic strategies have intensified efforts in this
area. Two primary reasons behind the development of this key area of chemical
research are: (i) the controlled synthesis of large mixed main group metal semiconductor nanoparticles and nanoclusters leads to a size regime wherein the electronic
properties of these molecules no longer resemble those of smaller, discrete molecular units nor do they mimic those of the corresponding bulk materials, and such
complexes hold great promise for use in future electronic applications. (ii) The use
of discrete ‘premixed’ binary or ternary clusters, with labile ancillary ligands may
afford alternate, low temperature routes to corresponding (and possibly new) solid
state materials. The use of preformed molecules in the preparation of solids allows
lower reaction temperatures for the formation of solids, thus implying kinetic
versus thermodynamic control during sample preparation.
Two crucial factors required for the successful development of these applications
are the need to synthesize the appropriate nanocluster molecules in such a manner as to have zero size distribution and to be able to structurally characterize the
products obtained. The numerous practical applications of binary late-metal chalcogenide semiconductors [1] have spurred the development of chemical methods to
access nanometer-sized pieces of these solid materials, where single crystal diffraction can be used to elucidate the three-dimensional structure of the clusters
obtained.
The flexibility of chalcogenide (E
2À ) and chalcogenolate (RE
À ) ligands is demonstrated in their ability to adopt several different bridging coordination modes
and to form stable bonds with most transition and post-transition metals [2–9].
This tendency to bridge metals is attributed to the highly polarizable electrons and
the anionic nature of these ligands. As a consequence of the bridging ability, binary
metal chalcogenides are typically nonmolecular solids, with extensive bonding in
one, two, or three dimensions. Access to molecular metal chalcogenide clusters
418
Large Semiconductor Molecules
J. F. Corrigan and M. W. DeGroot
13.1
Introduction
The synthesis of large, discrete molecular complexes with several dozen, or indeed
several hundred, heavy atoms is currently the focus of numerous research efforts
worldwide and recent successful synthetic strategies have intensified efforts in this
area. Two primary reasons behind the development of this key area of chemical
research are: (i) the controlled synthesis of large mixed main group metal semiconductor nanoparticles and nanoclusters leads to a size regime wherein the electronic
properties of these molecules no longer resemble those of smaller, discrete molecular units nor do they mimic those of the corresponding bulk materials, and such
complexes hold great promise for use in future electronic applications. (ii) The use
of discrete ‘premixed’ binary or ternary clusters, with labile ancillary ligands may
afford alternate, low temperature routes to corresponding (and possibly new) solid
state materials. The use of preformed molecules in the preparation of solids allows
lower reaction temperatures for the formation of solids, thus implying kinetic
versus thermodynamic control during sample preparation.
Two crucial factors required for the successful development of these applications
are the need to synthesize the appropriate nanocluster molecules in such a manner as to have zero size distribution and to be able to structurally characterize the
products obtained. The numerous practical applications of binary late-metal chalcogenide semiconductors [1] have spurred the development of chemical methods to
access nanometer-sized pieces of these solid materials, where single crystal diffraction can be used to elucidate the three-dimensional structure of the clusters
obtained.
The flexibility of chalcogenide (E
2À ) and chalcogenolate (RE
À ) ligands is demonstrated in their ability to adopt several different bridging coordination modes
and to form stable bonds with most transition and post-transition metals [2–9].
This tendency to bridge metals is attributed to the highly polarizable electrons and
the anionic nature of these ligands. As a consequence of the bridging ability, binary
metal chalcogenides are typically nonmolecular solids, with extensive bonding in
one, two, or three dimensions. Access to molecular metal chalcogenide clusters
418