Chemistry and Biochemistry
John C. MacDonald
Associate Professor
Department: Chemistry & Biochemistry
Professional Page
Office: Life Sciences and Bioengineering Center, 3022
Phone: +1-508-831-5240
Fax: +1-508-831-5933
jcm@wpi.edu
Research
Molecular nanotechnology has emerged as one of the most high impact fields of research in chemistry and materials science. The hallmark of molecular nanotechnology is the design of molecular scale devices and structures with useful properties that arise from the collective interaction between different molecular components. Consequently, we are striving to better understand processes such as molecular recognition, molecular templating, and supramolecular assembly at interfaces and in solutions and solids in order to develop strategies to fabricate devices and materials with useful optical, electronic and physical properties. Our research currently centers in three areas that involve supramolecular assembly of molecules in bulk molecular crystals and in multilayer thin films on surfaces, as well as crystallization of drugs and proteins on chemically modified surfaces as a means to control nucleation and the incidence of polymorphism.
Our primary goal in working with molecular crystals is to develop new types of solid materials with channels or cavities that exhibit nanoporous host-guest behavior and useful optical properties. There is a growing need for such materials for application in molecular separations, molecular storage and delivery, and molecular sensors. Our research involves noncovalent assembly of organic molecules or coordination compounds into well- defined, predictable architectures in two and three dimensions via hydrogen-bonding interactions and metal-ligand coordination with transition and lanthanide metals. We recently developed several unique classes of layered materials in which transition or lanthanide metals can be mixed or segregated in an organic host and that luminescent emission of these materials can be controlled by design.
We also are interested in developing strategies based on molecular templating to fabricate multilayer thin films on surfaces that exhibit photovoltaic behavior. We recently demonstrated that monolayer films on gold with dicarboxypyridines exposed at the surface could be used to control multilayer deposition of thin films of redox active chromophores such as pyrene that generate photocurrent when exposed to light. We currently are expanding on this work to explore modification of important surfaces other than gold such as silica and silicon, to investigate using new redox active chromophores or combinations of different chromophores, and to optimize energy and electron transfer by linking several layers of electron donors and acceptors through multilayer assembly.
Crystallization of drug molecules and proteins from solution as polymorphs-that is, different crystal forms in which the molecules adopt alternate packing arrangements-remains a persistent problem for crystal engineering and molecular assembly in crystalline solids. Polymorphism is particularly problematic in the development of pharmaceuticals because polymorphs of a single compound legally are classified as different drugs. Consequently, there is a need to develop methods to screen for the incidence of polymorphs and identify and control which polymorphs form. We are investigating whether nucleation and growth of crystals of pharmaceuticals such as barbital and acetaminophen can be controlled on surfaces using self-assembled monolayers (SAMs) of organic molecules on gold, glass or zeolites as substrates. We also are investigating whether crystals of proteins such as lysozyme can be grown on these surfaces. Ultimately, we aim to fabricate microfluidic devices with multiple channels to screen for polymorphs using simultaneous high throughput crystallization on a range of surfaces.
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