FY2010 - Oak Ridge National Laboratory

Director’s R&D Fund—
Science for Extreme Environment: Advanced Materials and Interfacial Processes for Energy
directed self-assembly of soft materials have emerged from advances in supramolecular chemistry and
crystal engineering, general methods for implementing these concepts do not exist. Moreover, materials
self-assembled from organic building blocks are often fragile and intolerant to extreme conditions. This
project addresses these limitations by utilizing a computer-aided design approach for molecular building
blocks that are structurally encoded to create targeted assemblies of predictable architecture and
dimensions, and validating the approach by producing robust crystalline materials via dynamic covalent
chemistry (DCC). The design strategy entails a novel hierarchical approach (1) involving DCC selfassembly
of nanoscale polyhedra and (2) using these polyhedra as nodes for the DCC self-assembly of
crystalline networks. Successful accomplishment of this project will represent a fundamental
breakthrough in the design and synthesis of advanced functional materials for energy applications,
providing a rational approach to a new class of well-characterized three-dimensional organic materials
with unprecedented chemical and thermal properties.
Mission Relevance
This research presents a new paradigm in the synthesis of soft materials, coupling computational insight
with dynamic covalent chemistry to achieve an unprecedented level of architectural control from the
molecular to mesoscale. The results will provide proof-of-principle for the existence of a rational route to
a novel class of robust, crystalline organic materials with deliberately tailored structures and properties,
laying the foundation for understanding the relationship between structure and function, and ultimately
enabling the design and control of matter needed to develop inexpensive and plentiful sources of energy.
Thus, the research proposed herein is expected to benefit DOE Office of Basic Energy Sciences (BES)
initiatives where functional organic materials play a role, such as catalysis, energy storage, CO 2
sequestration, solid-state lighting, and solar energy utilization.
Results and Accomplishments
Research has concentrated on the forming of organic crystals using reversible imine formation as the
coupling reaction. This involves the reversible coupling carbonyl compounds (aldehydes or ketones) with
amines. The strategy is to use carbonyl compounds either as vertices for tetrahedral building blocks or as
nodes for frameworks. Both tri- and tetra-carbonyl substituted molecules were identified as synthetic
targets.
To date five tetracarbonyl nodes and five tricarbonyl vertices have been prepared and purified in gram
quantities. Computer-aided design runs using in-house HostDesigner software identified diamine
molecules that offer the correct structural characteristics to direct the formation of the desired assemblies.
Candidates identified by HostDesigner were evaluated with the MM3 model, after validating performance
against a large amount of imine crystal structure data. Novel algorithms were derived and coded to
generate powder diffraction patterns for comparison with experimental data.
Systematic studies have been conducted to identify general reaction conditions (solvent, added water, pH,
temperature, and time) to optimize imine formation. Although it was possible to reproduce the formation
of a DCC framework that appeared in the literature after this project was initiated, all attempts to form
new frameworks have thus far been unsuccessful, leading instead to amorphous polymers or gels. It is
anticipated that some of these highly cross-linked materials may exhibit high surface areas, and
characterization using gas adsorption methods is under way.
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