Synthetic efforts at the Center for Molecular Design and Recognition (CMDR), located on the fifth floor of the Goodyear Polymer Center at the University of Akron and founded by Professor George R. Newkome, a pioneer and founding father of dendrimer chemistry, are focused on the investigation of new molecules, polymers, and nanoscopic constructs that possess unique architectures and utilitarian features. Over the years, this has led our group to become involved in the preparation of numerous supramolecular and heterocyclic structures such as crown ethers, rotaxanes, and polypyridines. Presently, we are concentrating on the construction of highly branched architectures, currently known as dendrimers and hyperbranched polymers, along with their attendant properties. Associated with the construction of these macromolecules is also the design and preparation of building blocks that facilitate a modular synthetic approach aimed at the ability to fine tune the desired properties of higher order structures such as functional group density, internal void volume, hydrophilicity/lipophilicity, mode of assembly, and molecular recognition capability.
An example of the versatility of this approach is evident in the ability to prepare the molecular equivalent of a "Rubik's Cube" termed a "Rubik's Sphere" (pictured in the upper left hand corner of this page). The Rubik's Sphere can be envisioned by considering the grafting of building blocks, or spherelets (analogous to cubelets), with differing terminal functionality to the surface of a spherical polymer (a dendrimer) whereby the properties of bond and branch rotation produce a dynamic and heterogeneous surface. Ramifications include the potential for terminal groups or units to rotate to 'separated' or 'adjacent' conformations which in turn affords the foundation to begin to control relative functional group positional parameters in large molecules. Other current projects in our laboratories involve the preparation of ligands with multiple metal attachment sites configured to facilitate the self-assembly of higher order architectures that span the organic-inorganic interface.
Synthetic efforts are also focused on the self-assembly of multiple metal arrays, where the metal juxtaposition is strictly controlled. This has led to the development of protocols that facilitate the creation of nanoscale, polymetal materials capable of acting as electron storage devices. To date, Ru-, Fe-, and Os-based arrays have been prepared, along with some mixed-metal constructs. Construction of these unique assemblies is predicated on the development of building blocks possessing architectural elements that allow the self-assembly process, such as the 120 degree terpyridine-terpyridine positioning that can easliy be incorporated into bisterpyridine ligands.
The self-assembly process is well-suited to the construction of materials possessing repeating molecular motifs at differing size scales. Thus, the construction of non-dendritic, "Fractal" molecular architectures is also a prime target in our laboratories.
© 2011 Center for Molecular Design and Recognition
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