The W. Allan Powell Lectureship in Chemistry

The Global Energy Challenge: Food and Fuel from Air, Water and Sunlight

Living healthy on a dying planet—we are a world out of balance. Relying on science to improve the health of the individual with the design of new drugs and therapies, we are neglectful of the health of our humanity at a global level. Disease indeed does compromise humankind’s very existence … but it is not disease inflicted on humans … rather it is the disease inflicted by humans on our planet. Climate change continues to outpace the implementation of renewable energy at an alarming rate. With an understanding that the underserved populations of our global society, without large energy infrastructures, will largely drive climate change by mid-century, our research is particularly focused on developing the science that underpins the implementation of distributed energy systems and processes for the developing world.

Hybrid inorganic | biological constructs have been created to use sunlight, air and water as the only starting materials to accomplish carbon and nitrogen fixation, enabling the establishment of distributed and renewable Fischer-Tropsch and Haber Bosch cycles. The carbon and nitrogen fixation cycles begin with the Artificial Leaf, which was invented to accomplish the solar fuels process of natural photosynthesis—the splitting of natural water to hydrogen and oxygen using sunlight—under ambient conditions. The hydrogen from the Artificial Leaf may be interfaced with metabolically engineered organisms to power the Bionic Leaf-C and Bionic Leaf-N to convert carbon dioxide and nitrogen from air into liquid fuels and ammonia, respectively. The Bionic Leaf-C performs artificial photosynthesis to form biomass or liquid fuels at solar-to-biomass energy efficiencies that exceed the best growing crops by a factor of 10 and exceed natural biomass-to-liquid fuels efficiencies by a factor of >100. The Bionic-Leaf N is a living biofertilizer that can replace chemical fertilizer; field trials have demonstrated massive carbon dioxide budget savings (e.g., for a 400-acre farm, 154 metric tons of CO2 is mitigated) while enhancing crop yields without the run-off that is responsible for harmful algal blooms.

Where are these innovations useful? The use of the simple inputs of only sunlight, air and water to produce fuel (carbon neutral) and food and vitamins (carbon negative) within a sustainable cycle for the biogenic elements of C, N and P is particularly useful to the poor of the world, where large infrastructures for fuel and food production are not tenable.

Presentation: 2020 Powell Lecture Slide.pdf

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The Road to a Sustainable Energy Economy Modern society runs on the energy stored in fossil fuels. This dependency is not sustainable. The harvesting and use of the energy that comes to us from the sun depends on our ability to store electric power. The means to store electric power in different rechargeable electrochemical cells are compared, and a view of the status of the materials to enable a solution will be presented. As a material science pioneer, Prof John Goodenough’s discovery and characterization of Lithium Cobalt-Oxide and Lithium Iron Phosphate made the modern Lithium Ion Battery possible, and has made them ubiquitous. From growing up in a Connecticut farmhouse with a “kerosene stove and an icebox for food,” Dr. Goodenough has spent a lifetime thinking about energy.As a result, his discoveries have had a major impact on literally everyone. And now at age 95, his latest discovery promises a new kind of battery that would be so cheap, lightweight, energy dense, and safe that it could revolutionize the energy landscape, in addition to revolutionizing the electric car. So, come join us as we hear the amazing story of this amazing scientist

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Organometallic Synthesis and Mechanisms: The group examines the fundamental organometallic chemistry required for the design and synthesis of catalysts for use in organic and polymer synthesis. Catalysts for olefin metathesis have been the focus of the research over the past several years. A family of ruthenium catalysts has been developed that has opened a wide variety of applications for olefin metathesis. The tolerance of these catalysts to functional groups and their ease of use have been the keys to their broad use. Underlying the development and improvement in these catalysts has been a detailed understanding of their mechanism of reaction. Continuing efforts are being made to further improve and broaden the use of these catalysts. These studies involve ligand and new transition metal complex synthesis as well as continuing examination of the mechanistic features that control the activity and selectivity of these catalysts. Recently the Division has created the Center for Catalysis and Synthesis. Our group is using the center for the rapid screening for the new catalyst systems.

Organic Synthesis and Reagents: Over the past several years a number of olefin metathesis based transformation have become important in organic synthesis. The most broadly use method is ring closing metathesis (RCM) to form a variety of rings. Five to over 82 membered rings have been prepared in good yield using olefin metathesis. The functional group tolerance of the ruthenium based catalyst allows complex molecules to be prepared without protecting groups. Definition of the rules controlling the use of cross metathesis in organic synthesis has opened its application to the synthesis of a variety of functional molecules. A variety of related reactions involving tandem and acetylene metathesis are also being used. The focus of the group at this time is on the synthesis of more active and selective systems. Catalysts that provide high enantioselectivity in RCM and high stereoselectivity in cross metathesis are being developed. Other metal catalyzed reactions that provide new routes to acetylenes and alcohols are being studied.

Polymer Synthesis: Ring opening metathesis polymerization (ROMP) has opened new methods for the synthesis of highly functionalized polymers with controlled structures. By tuning of the structure of the ruthenium based metathesis catalysts, the opportunities have been greatly expanded. Recent methods have been developed that are being used to prepare cyclic olefins, alternating copolymers and multiblock copolymers with a broad array of functionality. The properties and applications of these new materials are being explored.

The passage of the Bayh-Dole Act in 1980 enabled universities to own intellectual property developed from within and thereby catalyzed the creation of an alternative pathway for drug discovery. This presentation will attempt to define the role of research universities in the drug discovery/development process and place it in its proper perspective vis a vis the more traditional pathways followed in the pharmaceutical and biotechnology industries.

In particular, we have created an innovative model for expediting drug development at research universities. The Emory Institute for Drug Development (EIDD) was founded in 2009 to discover therapeutic agents to treat infectious diseases, particularly viral diseases. The EIDD has the personnel, laboratory space and equipment necessary to conduct the key preclinical activities required to bring a drug into clinical development.

DRIVE, the “industrial partner” of the EIDD, is organized as a virtual drug development company with a highly experienced management team. As a non- profit (501(c) (3)) entity, it is able to in-license attractive development opportunities from Emory or elsewhere on commercially favorable terms. Then, either by using its own seed capital or by raising external funds, it can utilize the EIDD and/or external vendors to move these opportunities quickly and efficiently down the development continuum to meet the critical need for new therapeutic agents to treat emerging infectious disease. DRIVE has been designed to be a self-sustaining entity, i.e., the company can reinvest its earnings from out- licensing or sale of assets in new development opportunities as they emerge.

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Breakthroughs in Imprint Lithography and 3D Additive Fabrication

There is a renaissance underway today in research that is being fueled by the DIY (do-it-yourself) culture that is generally referred to as the "Makers Movement". The maker culture exploits new tools for fabrication and encourages invention and rapid prototyping. Such tools in combination with an innovative mindset will make major impacts in many fields, including drug delivery technologies. This lecture will describe breakthroughs in the Makers Movement - including an off-shoot of imprint lithography used to mold individual drug particles and drug delivery vehicles, and a pioneering advance in 3D additive manufacturing that is continuous, moldless and not longer layer-by-layer.

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Chemical Tools For The Study Of Complex Biological Systems

This presentation will discuss the development and application of new chemical probes for studying complex biological systems. Due to the essential signaling roles played by intracellular protein phosphorylation, the focus of recent studies in the group has been on protein kinases as critical targets for probe development. In the area of signal transduction, new approaches including general strategies for the assembly of synthetic and semi-synthetic probes for interrogating the specific function of proteins involved in directed cell migration and cell cycle control have been developed. These probes include novel fluorescent amino acids for interrogating the dynamics of protein kinase activities and phosphorylation-dependent protein-protein interactions in addition to methods for the assembly of caged phosphopeptides and proteins for examining phosphorylation-mediated cellular activities.

Ultimately, an arsenal of chemical probes for monitoring protein phosphorylation and chemically caged analogues of key phosphoprotein mediators will contribute to the understanding of the spatial and temporal profiles of protein kinases and phosphoproteins in complex cellular pathways.

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The Role of Science in Moving the Planet to Green Energy and a Sustainable Future [Watch Lecture]

High Frequency Dynamic Nuclear Polarization: Why Two Electrons Are Better Than One [Watch Lecture]

The Solar Army

The sun is a boundless source of clean energy, but it goes down every night. We and many others are trying to design solar-driven molecular machines that could be used on a global scale to store solar energy by splitting water into its elemental components, hydrogen and oxygen. Hydrogen is a clean fuel that could be used directly or combined with carbon dioxide to produce methanol, a liquid fuel. We are working on rugged light absorbers and catalysts made from Earth abundant materials that have the potential to split water as efficiently as natural photosynthesis. We have recruited hundreds of students to join a Solar Army whose mission is the discovery of brand new metal-oxide catalysts for our solar water splitters.

Harry B. Gray is the Arnold O. Beckman Professor of Chemistry and the founding director of the Beckman Institute at the California Institute of Technology. After graduate study and research at Northwestern University and the University of Copenhagen, he joined the chemistry faculty at Columbia University, where he worked on the electronic structures and reactions of inorganic complexes. He moved to Caltech in 1966, where his work in biological inorganic chemistry has shed light on the factors that control electron flow through proteins. He has received the National Medal of Science from President Ronald Reagan (1986); the Priestley Medal (1991); the Harvey Prize (2000); the Wolf Prize (2004); the Welch Award (2009); and 16 honorary doctorates. He is a member of the National Academy of Sciences; the American Philosophical Society; the Royal Danish Academy; the Royal Swedish Academy; the Royal Society of Great Britain; and the Accademia Nazionale dei Lincei.

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Chemical-Biological Interfaces in Endocrinology: Nuclear Receptors, Modulating Ligands, and Drug Discovery

A basic concept in endocrinology is control of activities and processes at distal sites in the body. Signaling molecules, in some cases non-protein small molecule hormones, traverse the body and ultimately relay their chemically encoded information to a protein receptor at the target tissue. The nuclear receptor (NR) superfamily, particularly the steroid receptor sub-family, contains classic examples of receivers for small chemical messengers. The NR is a well-adapted receptor for this type of function because it not only can specifically bind the small molecule, but it is capable of transducing a complex set of signals, typically transcript-related, encoded by the properties of the ligand. The nature of the information that the ligand bound-NR relays also depends on a complex interplay of factors including coactivator partners and cell type. Our work over the past several years has focused on discovery of novel NR-modulating molecules and understanding the properties of the compound-bound NR through chemistry, crystallography, biophysical, and cellular studies. The ultimate goal of our work is to develop therapeutics of a variety of disease states including metabolic, inflammatory, and cancer-related conditions.

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Polymer Electronics For Chemical And Biological Sensors

This lecture will describe the conceptual design and optimization of chemical/biological sensors based upon conjugated polymers (CPs) and carbon nanotubes (CNTs). The ability of a CP to produce amplification in a fluorescence- or resistance-based chemosensor stems from its ability to transport optical excitations or electrical charge, respectively, over large distances. These transport properties provide the increased sensitivity and versatility of CPs and CNTs over small-molecule chemosensors. By adding new functional diversity to CPs and CNTs chemoresistive properties have been realized. In a fluorescence sensors, the migration of an optical excitation increases the probability of an encounter with an occupied binding site. We originally demonstrated this scheme making use of analyte induced quenching and have also demonstrated how local reductions in the polymers bandgap produce wavelength shifts in emission. To impart recognition to our polymers we have made use of a variety of molecular recognition schemes, assemblies, and reactions. Recent applications of amplifying polymers in biosensory schemes will be discussed.

A number of different methods can be used to impart analyte selectivity to electronic polymer sensors. These involve designed receptors, modifications to the energy levels of the polymers, and coupling to other key reactions. I will detail some of our latest results in these directions.

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Formal Powell Lecture PowerPoint

All The Ways to Have A Bond

Any rigorous definition of a chemical bond is bound to be impoverishing, leaving one with the comfortable feeling "yes (no), I have (do not have) a bond," but little else. And yet the concept of a chemical bond, so essential to chemistry, and with a venerable history, has life, generating controversy and incredible interest. Even if we can’t reduce it to physics. I will discuss some of the common criteria: length, energy, force constants, magnetism, energy splittings and other spectroscopy criteria, bond orders, population analyses, and bond critical points. My advice is likely to be: Push the concept to its limits, accept that (at the limits) a bond will be a bond by some criteria, maybe not others, respect chemical traditions, have fun with the richness of something that cannot be defined clearly, and spare us the hype.

Dr. Hoffmann decided to change the subject of his talk and instead talk about Mr. and Mrs. Lavoisier (amongst others).

Holding Single Molecules up to the Light: From in vitro to in vivo Studies

At the single molecule level, a chemical reaction occurs stochastically. We study ever-fluctuating single enzyme molecules and reconcile their enzymatic kinetics with the classic Michaelis-Menten equation. In addition, we have developed new methods to probe spontaneous as well as functionally important conformational dynamics in an intact protein. In a living cell, gene expression is by definition a single molecule problem because of one or two copies of DNA and low copy numbers of most mRNA and some proteins that are involved in the gene expression process. Stochastic events of gene expression give rise to different phenotypes among genetically identical cells or organisms. We have developed methods for probing gene expression at the single molecule level, yielding new and quantitative information regarding the fundamental processes in living cells.

Supersonic Jet Spectroscopy: From Diatomics to Biological Molecules

Using traditional techniques, it is difficult to observe and analyze the high-resolution gas-phase spectra of any but the smallest molecules: diatomics, triatomics, and somewhat larger molecules which have some symmetry to aid the analysis. Supersonic jet spectroscopy is a technique which greatly simplifies a molecule’s gas-phase spectrum and extends the range of gas-phase spectroscopy to much larger species. In the lecture I will describe the technique and try to explain why it does what it does: i.e. why a supersonic jet expansion produces well-resolved spectra of large molecules. I will illustrate the lecture with examples of van der Waals molecules and molecules of biological interest which are usually not observed at all in the gas phase.

Environmentally Benign Green Chemical Process

Non-traditional tunable solvents for sustainable chemical processes have been developed in our laboratories over the past decade. These include (1) supercritical fluids (CO2, ethane, etc.), (2) near critical water, (3) ionic liquids, (4) gas-expanded liquids (GXLs), (5) fluorous biphasic systems, and (6) organic-aqueous tunable systems (OATS). Examples of reactions and processes (substitutions, alkylations, etc.) employing each of these solvent systems will be presented along with mechanistic insights.

The Discovery of Alimta™, A Broadly Effective New Antitumor Agent

The pteridine ring system was first identified in a study of the constituents of butterfly wing pigments, and pteridines thus were initially viewed as occupying an esoteric, insignificant corner of natural product chemistry We now know, however, that two pteridine derivatives, the molybdenum cofactor and folic acid, are critical components of all living cells, and are required for all forms of life. Cofactors derived from folic acid play key roles in a host of diverse metabolic reactions essential for the formation of DNA, RNA, ATP, amino acids and proteins. Our long-time fascination with pteridine chemistry has developed into a search for inhibitors of folate-dependent enzymes, and led a few years ago to the discovery that (6R)-5,10-dideaza-5,6.7,8-tetrahydrofolic acid (lometrexol) blocked de novo purine biosynthesis, and exhibited excellent therapeutic activity against a variety of solid tumors. These initial observations initiated an intensive search for further inhibitors of folate-dependent processes. This effort has culminated in the discovery of a remarkable new oncolytic agent, Alimta™ (pemetrexed disodium, now under development by Eli Lilly & Company). Alimta™ exhibits an unprecedented breadth of antitumor activity that results from inhibition of at least five of the major folate-dependent enzymes in cellular metabolism. Every type of solid tumor thus far examined clinically has responded to this new agent. Alimta™ is now in multiple advanced Phase II/III trials and has recently been approved for compassionate use in mesothelioma. This lecture will attempt to describe the tortuous explorations that eventually led to the discovery of Alimta™, its current clinical status, and our understanding of its unique mode of action.

An Organometallic Carousel: Abnormal Binding of Heterocyclic Ligands

Organometallic catalysis, widely employed in organic and industrial chemistry, relies on metal complexes that contain permanent ligands that endow the catalyst with the desired selectivity properties, such as enantioselectivity in asymmetric catalysis. Phosphines (PR3), the ligands used most widely to date, are extremely effective but give catalysts that are generally air- and heat-sensitive. In recent years, ’carbene’ ligands derived from imidazolium salts have given equally impressive catalysts in terms of selectivity and activity, but these now tend to be much more air and thermally stable.

We now show that such carbenes can be formed for Rh, Ir, Pd and Pt by simpler and milder synthetic pathways than currently used. These allow access to chelating carbenes with more complex structures than previously possible. Not only imidazolium, but also triazolium-derived ligands are possible. Abnormal binding at the ’wrong’ carbon — never previously seen — can occur for both heterocycles. The ratio of normal to abnormal binding is very sensitive to the counterion, posing interesting mechanistic issues. NMR work allows the ion pair solution structure to be deduced and compared with that predicted from DFT calculations. High catalytic activity is seen in several cases, strongly depending on the structure of the catalyst. Abnormal imidazolium binding may have bioinorganic significance because histidine could in principle bind via carbon as well as the classical binding via N. Abnormal ligand is discussed.

Cellular Signaling with Nitric Oxide: A Collision Course for Chemistry and Biology?

Chance observations and serendipity have often played a prominent role in scientific discoveries. This is especially true in what has become known as the nitric oxide (NO) story. Nitric oxide is toxic and is a component of smog and cigarette smoke, but it has also been found to be made normally by animals including humans. NO is synthesized by the enzyme nitric oxide synthase which converts the amino acid L-arginine to citrulline and NO. NO functions in biology in two very important ways. First it has been found to be a messenger by which cells communicate with one another (signal transduction) and secondly has been found to play a critical role in the host response to infection. In the host response to infection, it appears that the toxic properties of NO have been harnessed by the immune system to kill or at least slow the growth of invading organisms. The non-specific chemical reactivity with key cellular targets is responsible for this action. In signaling, NO directly activates the enzyme guanylate cyclase (sGC). Once activated, sGC converts GTP to cGMP and pyrophosphate. The cGMP formed is responsible for the well-documented actions of NO such as blood vessel dilation. With the initial discovery of NO signaling, several important questions emerged that centered largely on the issue of how a signaling system functions when the signaling agent is chemically reactive (short-lived), highly diffusible, and toxic. Critical, especially in signaling, is the control of NO biosynthesis and interaction with the biological receptors at a concentration that will not harm the host. Why did nature choose NO? That question engenders only speculation. How does NO work (i.e. what does NO do and how does it do it without harm)? Answers to those questions can now be offered as an interesting picture of molecular level details emerges.

Forty-three Years of Photochemistry

The first half of the presentation will review some highlights of forty-three years studying photochemistry from 4K to 300K: unusual reaction mechanisms, strange intermediates, and weird structures. The second half of the lecture will feature unpublished research that grew from the earlier photochemical studies: novel quinoid systems with very low triplet energies, new linear acenes, and the synthesis of supercene.

Peptide and Protein Analogues Containing Synthetic Amino Acids at Defined Positions

The information that specifies the structure of the proteins utilized in living organisms is encoded in their DNA. The decoding process involves several intermediate species, notably messenger RNAs and transfer RNAs, the latter of which are ordinarily activated uniquely with their cognate amino acids. The fidelity of this activation process is both extraordinary and absolutely essential for the elaboration of proteins containing the intended amino acid at each position. By the use of messenger RNAs, containing unique codons at predetermined sites and intentionally misacylated transfer RNAs, we have been able to prepare proteins containing synthetic amino acids at predetermined positions, i.e., we have increased the number of building blocks that can be used to assemble protein structures. This will be illustrated in the lecture by the formation of analogues of firefly luciferase that emit light of altered wavelength.

We have also used misacylated tRNAs to inquire about the ability of the peptide bond-forming apparatus to catalyze the formation of modified peptide-like linkages that do not normally occur in nature. This will be illustrated by consideration of a ribosome-mediated nucleophilic displacement reaction.

Chemically Modified Electrodes 25 Years Later

Our first research on designed chemical bonding of monolayers of chemical species to electrode surfaces began in 1974 and was reported in Analytical Chemistry in 1975. This lecture will trace some consequences of the chemically modified electrode idea from then to the present. The 1970’s emphasis on monolayers thickened in the 1980’s to ultrathin polymer films and thinned again in the 1990’s to self-assembled monolayers and monolayers in three dimensions. The idea has been augmented by inventions of many laboratories and by mergers with other, diverse lines of interest such as model organic surfaces, solid state transport, high temperature superconductors and quantum particles. These merges illustrate the interdependencies of progress in science.

The Chelate Effect in Binding Catalysis, and Chemotherapy

Enzymes and antibodies generally bind substrates using multiple interactions, leading to high binding constants for antigens or for transition states. We have prepare a series of receptors that combine two cyclodextrins, and find that with substrates having the correct geometry the affinities can be extremely high, approaching that of the best antibodies. At the same time, when catalytic functional groups are incorporated into such molecules, high rates and selectivities are observed for catalyzed reactions.

Enzymes also commonly use two (or more) catalytic groups to achieve their high effectiveness. We will describe systems that imitate this feature, and evidence for the mechanisms used by our bifunctional catalysts. In some cases these studies also furnish insights into the mechanisms of the corresponding enzymatic processes.

These ideas have also been incorporated in the design of a novel class of cytodifferentiating agents that show promise in cancer treatment. The current state of this work will be described.

Challenges and Rewards of Pharmaceutical Research

A biochemical approach to chemotherapy based on interference with nucleic acid synthesis by purine and pyrimidine antimetabolites has led to a number of important medicinal agents. The antileukemic drugs 6-mercaptopurine and thioguanine resulted from this program. These were the first purine antimetabolites used successfully in the treatment of acute leukemia and have remained, even after 40 years, an important part of the armamentarium against leukemia.

Studies on the metabolism of 6-mercaptopurine (6-MP) led to the realization that much of the compound was converted to inactive compounds in the body. Derivatives were synthesized which could act as pro-drugs of 6-MP. One of these, azathioprine (Imuran®) proved to be the drug of choice for suppressing the immunological rejection of transplanted organs. As a result of the use of azathioprine, many thousands of kidney transplant patients have enjoyed a long-term survival of their grafts.

The studies of purine metabolism also led us to the investigation of the in vivo inhibition of the enzyme xanthine oxidase with allopurinol. This purine analog not only potentiated the activity of 6-MP, but also inhibited the formation of uric acid. Allopurinol has become a standard treatment for gout and for the prevention of uric acid kidney stones.

In the 1970’s we developed a new antiviral agent, acyclovir, for the treatment of herpes virus infections. This drug is a purine nucleoside derivative which has an acyclic side chain at the position ordinarily occupied by a deoxyribose moiety in DNA. It is non-toxic to normal cells but is activated in herpes virus-infected cells to form a compound which is toxic to the virus. The high selectivity and safety of acyclovir have made it an effective agent for treating cold sores, herpes keratitis, genital herpes, herpes encephalitis, chickenpox and shingles. It has also been successful prophylactically in preventing recurrences of genital herpes in patients who suffer from frequent recurrences. Acyclovir was a landmark in antiviral chemotherapy because it proved it was possible to have a drug with a good safety profile that was active against DNA viruses.

Enantioselective Carbon-Carbon Bond Forming Reactions

Chiral cationic Cu(II) Lewis acid complexes are used for catalysis of the Diels Alder and aldol reactions. Both cycloaddition and aldol processes may now be efficiently catalyzed with enantioselectivities in excess of 90%. Issues pertaining to the structure of the catalyst-subtrate complexes, the problems of product inhibition, and the reaction scope for these reactions will be surveyed.

Technology Policy For Economic Growth and Competitiveness

As the United States adapts to the new world economy and pursues an economic growth agenda, a new approach to technology policy is emerging. It rests on the strong linkage between technology and economic growth, and provides a new framework for the role of government in helping private firms develop and profit from innovations. While this new policy is channeling more Federal R&D resources to projects of commercial relevance, it is also resulting in Federal programs that go beyond R&D to initiatives which promote industrial competitiveness.

The private sector is the customer for government programs directed towards improving competitiveness and customer perceptions are paramount. Industry perceives significant impact on competitiveness from incentives for capital formation, regulatory reform, improving education and training, the modernization of manufacturing , and a greater voice in R&D policy. The Clinton Administration has made progress in many areas of business concern including market opening initiatives, education reform and workplace upgrading, modern infrastructure, manufacturing extension, and industry involvement in technology programs.

Discovering and Exploring a New Continent of Chemistry

Fifty years ago, diborane was a chemical rarity, available only in two laboratories in the world. The requirements of research during World War II led to the discovery of practical synthetic methods for diborane and to the discovery of sodium borohydride. These turned out to be excellent reducing agents in organic chemistry. Exploration of these reducing characteristics led to the discovery of hydroboration. Hydroboration made organoboranes readily available. These organoboranes have proven to be the most versatile intermediates now available for organic synthesis. Recently this program has provided the first general synthesis of pure enantiomers. It is a rare experience to carryon a continuous research program for fifty years. This program has led not only to major industrial developments and to the Nobel Prize, but to insights into the methods for productive research.

Photoreactions of Organic Molecules Adsorbed on Zeolitic Molecular Sieves

Photoreactions of molecules adsorbed on zeolites will be discussed, and a description of the microporous, crystalline structures of zeolites will be presented. It will be shown how the site of a molecule adsorbed on a zeolite may be determined experimentally and how the molecule’s site and the dynamics of reactive intermediates determine the photochemical products. Conversely, it will be shown how analysis of photoproducts can reveal information on the internal structure of zeolites and the zeolite/substrate complex.

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New Materials, New Phenomena: What’s Real in Molecular Electronics?

New materials have unique properties and associated phenomena of importance in new applications. “Molecular electronics” is an area of possible application for new molecular materials. Functionalization of the surfaces of closely spaced (about one micron), ultrasmall (2 x 50 microns), individually addressable gold wires with molecular materials has allowed the demonstration of molecule-based diodes and transistors. Such “devices” have unique characteristics stemming from the properties of the device-active molecular materials. The combination of polyaniline–and a poly(3-phenylthiophene)–based transistor will be shown to yield a distortion free push-pull amplifier. Unfortunately, such molecule-based devices are not fast, ultimately limited by ion motion. While not fast by solid state semiconductor device standards, the unique characteristics of the molecule-based system may be of practical consequence in some applications such as sensors.

Why 11-cis retinal for vision?

The chromophores of all visual pigments, the rhodopsins, is the 11-cis form of retinal and analogs bound covalently to opsin, the receptor protein, via a protonated Schiff base linkage. Similarly, the pigments present in Halobacterium halobium, namely, bacteriorhodopsin (proton pump), halorhodopsin (chloride pump), and the two sensory rhodopsins (phototaxis receptors) contain the all-trans isomer of retinal bound to the apoprotein by a protonated Schiff base linkage. The chromophores are indeed uniquely designed to perform such vital functions. Why was retinal chosen as the chromophore of pigments, why is the chromophore a protonated Schiff base, and why 11-cis in some cases and all-trans in other cases? These aspects as well as new findings from bioorganic studies on retinal proteins will be presented and discussed.

Single Collision Chemistry

Modern molecular beam and spectroscopic methods allow the observation of reaction products immediately after the single-collision events in which the new molecules are formed. This work has provided a detailed picture of the transfer of energy and angular momentum during the formation and decomposition of chemical bonds and the interconversion of energy among different kinds of molecular motion. The talk will illustrate the methods and prototype results in a largely nontechnical way and also will emphasize the interpretation of reaction dynamics in terms of electronic structure.

A Chemist’s View of Chemical Warfare, Courtship, and Mate Selection Among Insects

Insects often are defended by a wide variety of organic chemical weapons, some of which they synthesize and some of which they acquire from their food. Many insects also utilize organic chemicals (pheromones) for intraspecific communication. In the cases of some lepidoptera and beatles, we have been able to establish an unanticipated relationship among the compounds used as “aphrodisiac” pheromones. These studies suggest a possible pathway for the evolution of a chemical signaling system.

Analytical Chemistry From Fundamentals to Applications

Science is often thought to proceed in a straightforward fashion from theoretical principles to practical understanding. Indeed, a number of examples can be cited where the direct application of fundamentals leads to the solution of a pressing problem, However, in other situations, possible more numerous, a demanding problem is solved empirically and only later does a theoretical underpinning for the empirical solution develop.

In this presentation, examples will be taken from the field of analytical chemistry to show how this bi-directional interaction occurs and how it can be beneficial. In fact, in some situations, a cyclic interaction occurs between the discovery of fundamental characteristics about systems, measurements, or molecular interactions that can lead to important applications which,. in turn, require a more complete characterization of fundamental features. Importantly, instrumentation often plays an important part in the cyclic process and can be viewed almost as a chemical catalyst in the enhancement it provides.