Paul M. Lahti, Ph.D. - US grants

The use of computers in modern chemistry departments is becoming more and more essential for the support of meaningful research at the cutting edge of the field. The acquisition of an upgraded departmental minicomputer for the Chemistry Department at the University of Massachusetts at Amherst will be supported by both the Chemistry Shared Instrumentation Program and the Instrumentation for Materials Research Program. The acquisition will enhance the following areas of chemistry: 1) Computational modeling of molecules with unusual electronic and chemical properties. 2) Studies on the electronic structure of hole-molecules and the electronic states of molecular defects in condensed media. 3) Comparison of experimental and theoretical quadrupole coupling data in molecules. 4) The dissociation dynamics of molecules on metal surfaces.

This award is made by the Office of Special Projects in the Chemistry Division under the Materials Synthesis and Processing Initiative. This research will optimize the photochemical generation of phenoxy free radicals with regard to the type of substitution and the irradiation wavelength employed and apply the methodology to study electron exchange-controlled magnetic interactions in both molecular and polymeric systems. Solid state stable phenoxy polyradical systems will also be prepared and magnetic interactions in the solid state will be determined using spectroscopic and magnetic susceptibility techniques. %%% These fundamental structural and mechanistic investigations are directed towards developing rules to describe magnetic interactions both within and between molecules which may permit the design of a new generation of bulk organic ferromagnets.

The current rapid increase in the level of affordable computer hardware, and the ready availability of a variety of -computational chemistry software packages, have made molecular modeling accessible to all levels of the undergraduate curriculum. Construction and visualization of molecules have become valuable teaching tools, yet many chemical educators have had limited or no experience with this medium. This three year project will offer college faculty in New England and eastern New York an opportunity to learn about using molecular modeling in their undergraduate courses. A three and one half day workshop will be held each June at the University of Massachusetts, with a follow-up symposium to be held in January. Participants will gain familiarity with the basic theory and practical use of molecular mechanics and semi-empirical molecular orbital calculations and will receive a brief introduction to ab-initio methods. The emphasis of the workshop will be on the use of these techniques to teach and learn undergraduate chemistry. We will further advise the participants in establishing computational chemistry programs at their home institutions. During January participants and local educators from the Five-College region will be invited to the University to exchange success stories and discuss methods of incorporating modeling into undergraduate courses.

This award is made by the Office of Special Projects in the Chemistry Division. In this research program Lahti will investigate model organic molecules bearing unpaired electrons in order to understand how to design new materials with advanced magnetic properties. Structural and molecular interaction features which favor the production of high-spin interactions between electrons in bulk systems will be identified, leading to ferromagnetic domains which could be used in new magnetic media. In addition, polymeric polyradical systems having large numbers of unpaired spins will be designed and synthesized, and their magnetic properties will be investigated. These fundamental structural and mechanistic investigations are directed towards developing rules to describe magnetic interactions both within and between molecules which may permit the design of a new generation of bulk organic ferromagnets. Although practically useful materials have not yet been realized, recent progress holds much promise for synthesizing them in the future.

This award to Prof. Paul Lahti at the University of Massachusetts-Amherst is supported by the Advanced Materials and Processing Program in the Chemistry Division. The theme of the research is the synthesis, characterization and performance of molecular organic assemblies with multiple unpaired electrons as magnetic materials. Structural alterations will be developed in both polymeric arrays and solid state crystalline arrays which optimize interactions among the unpaired electron spins. Specifically, polymeric free radical systems will be made which maximize planarity, stable free radicals systems which interact through hydrogen bonded assemblies will be investigated, and free radical systems that assemble through metal chelation will be studied. The stable free radical types employed will be nitronyl nitroxides, iminoyl nitroxides and benzonitroyl nitroxides. Characterization will be by elemental analysis, ESR, NMR and GC-MS. Magnetic performance measurements will be carried out through established collaborations. This highly interdisciplinary research addresses fundamental mechanisms of organic ferromagnetism based on long range assembly of electronic spins. The combination of organic synthesis, stable free radical characterization, and magnetic performance measurements will provide an ideal environment for the training of students in problems of both fundamental interest and technological relevance. Additionally, many of the precursor and free radical species involved may have medicinal and pharmacological activity and will be made available for biological screening.

With this award from the Chemistry Research Instrumentation and Facilities (CRIF) Program, the Department of Chemistry at the University of Massachusetts in Amherst will acquire a CCDbased X-ray diffractometer. This equipment will enhance research in a number of areas including the following: a) synthesis of novel olefin polymerization catalysts; b) biomimetic solid-state syntheses of inorganic/organic composites; c) crystal structures of stable radicals and related precursor substances; d) studies of metallobiomolecules and synthetic model approaches; e) crystal engineering using functionalized diaminotriazines; and f) the design and construction of solid state materials using 'crystal engineering'.

The X-ray diffractometer allows accurate and precise measurements of the full three dimensional structure of a molecule, including bond distances and angles, and it provides accurate information about the spatial arrangement of the molecule relative to the neighboring molecules.

CTS- 0116498
MRI: Acquisition of an Instrumentation Cluster to Establish a Nanomagnetics Characterization Facility

Mark T. Tuominen
University of Massachusetts Amherst
$320,000

Abstract

New nanofabrication methods are emerging that serve to provide a pathway to single-domain magnetic terabit technology. Such data-storage density is equivalent to storing 25 full-length DVD-quality movies on a disk the size of a quarter. This grant involves the acquisition of an equipment cluster for characterizing the properties of designer nanoscale magnetic materials. This facility will consist of a three instruments: a SQUID-based magnetometer, a high-resolution magnetic force microscope (MFM), and a swept-field NMR probe. These instruments provide complementary experimental information that advances the development of nanomagnetic materials fabricated using self-assembly and chemical techniques. The SQUID magnetometer will be used to obtain magnetization characteristics on arrays of nanoscopic magnetic elements, including hysteresis curves, switching fields, coercivity, saturation magnetization, and remanent magnetization. The MFM will provide local magnetic information on individual nanoscopic elements, heterostructures, and patterned nanomagnetic media. The swept-field NMR probe will developed at UMass and be used to identify different crystalline phases and crystalline orientations of magnetic nanostructures through the swept-field spectrum.

These instruments will impact many different research projects and provide an education and training environment for numerous users. The facility will be used to develop techniques to engineer the magnetic properties of terabit arrays of magnetic elements made by oriented diblock copolymer templates. Magnetic behavior will be manipulated through nanowire growth conditions, array scale, and hybrid patterning. These efforts will be augmented by supplemental neutron and x-ray scattering measurements at National Laboratory facilities. The scope of this research is broadened by international, federal, and industrial collaborations. Unique configurations of magneto-transport devices will be developed and investigated using laterally patterned magnetic arrays, magnetic heterostructures, and engineered magnetic nanoparticle assemblies. New synthesis and assembly approaches will be explored in studies of molecular magnetism. Education and training activities include instrumentation training and nanofabrication process training through the use of interactive digital-video.

With this award from the Chemistry Research Instrumentation and Facilities (CRIF) Program, the Department of Chemistry at the University of Massachusetts Amherst will acquire a 400 MHz NMR spectrometer and refurbish a 200 MHz spectrometer. The new spectrometer will be a part of the High-Field NMR Facility at the university - a facility open to research of the Five Colleges Consortium (UMass, Smith, Mt. Holyoke, Amherst and Hampshire Colleges) and surrounding industries. This equipment will enable researchers to carry out research on the tacticity of, and branching in polyolefins; branching in dendritic and hyperbranched macromolecules; mechanistic investigations of copper-based catalysts for cross-coupling reactions; structures of conjugated polymers; thermodynamics of the unfolding/recognition process; and structural dynamics of amphiphilic polymers. These instruments will also play a vital role in training undergraduates and local area high school students.

Nuclear Magnetic Resonance (NMR) spectroscopy is the most powerful tool available to chemists for the elucidation of the structure of molecules. It is used to identify unknown substances, to characterize specific arrangements of atoms within molecules, and to study the dynamics of interactions between molecules in solution. Access to state-of-the-art NMR spectrometers is essential to chemists who are carrying out frontier research. The results from these NMR studies will have an impact in the development of novel polymers.

Intellectural Merits. Magnetic materials are worth billions in existing technologies. Chemical structure-based designs of new materials have much promise for new, useful types of electronic behavior. The PI proposes to make molecules with attached functional groups, which give specific magnetic and/or conductive properties. Stable organic radicals will be synthesized that are expected to self-assemble, for example, by using strongly directional hydrogen bonds. These organic pure solids, mixed solids, and hybrid systems (polymers containing radicals) will be tested for magnetic behavior and some for conductivity of electrical current as well. The most important scientific goals are: (1) to find good synthetic and purification methods to give materials that are stable and have potentially useful magneto-electronic properties; and (2) to discover new relationships linking molecular structure and crystal packing to magnetic and/or conductive properties.

Broader Impacts. Graduate students in this project will benefit from international exchange of expertise and collaborative ties, in particular with scientists from Brazil and Japan. Training will be highly interdisciplinary, including ways to make molecules, to determine how they assemble into solid packing patterns, and to correlate the patterns with magnetic or conductive behavior. Interdisciplinary training is vital in the modern techno-scientific marketplace, where projects have short timelines and workers must be adaptable and multi-talented. Communication skills will be emphasized by frequent group presentations, as well as presentations at national, regional, and/or local meetings.
The group has in recent years had more women than men, a reversal of the situation from 20 years ago. This made the group a "magnet" for other women to feel comfortable in joining a group that does much organic synthesis and math-oriented physical chemistry. For example, four of five Ph.D. degrees completed during 2006 in the Lahti group went to women. Interest in the work by female potential graduate students in recent entering classes has remained strong. The proposed work will also be linked to efforts to attract students from the UMass-Amherst-led Northeast Alliance for Graduate Education and the Professoriate (NEAGEP), an NSF-supported program that funds under-represented minority groups to pursue graduate scientific careers on our campus (http://www.neagep.org). Dr. Lahti and his group have been part of on-campus hospitability and recruiting of visiting students who are considering NEAGEP. This program will be an important resource for recruiting graduate student candidates from under-represented minority backgrounds into the field of materials science.