CAREER: Construction of Magnetic Cyanide-, Acetylide-, and Butadiynylide-Based Clusters

The primary objectives of the proposed studies are the preparation and characterization of molecule-based magnetic and photomagnetic clusters. A series of stable paramagnetic poly(pyrazolyl)borate cyanometalate precursors (building blocks) that exhibit large spin-orbit and/or spin state contributions to their magnetic ground states will be prepared. Using a building block synthetic approach, these building block complexes will be controllably aggregated into a series of magnetic and photomagnetic rectangular cluster derivatives, and the structural, magnetic, and photomagnetic properties will be investigated in collaboration with an international team of theoreticians, crystallographic, and magnetism experts. Questions concerning how anisotropic spin centers interact and contribute to the magnetic ground state, impact magnetic exchange, effective barrier heights, and quantum magnetization tunnelling will be probed in these rectangular clusters. Photomagnetic clusters will be prepared and fundamental magnetic bistability and optical intramolecular electron transfer processes probed via several active collaborations. Acetylide and butadiynylide complexes and clusters are expected to exhibit properties that are markedly different than cyanometalates. Several new and robust Cn-based complexes (building blocks) will be prepared and characterized via structural, magnetic, and spectroscopic techniques. Rectangular clusters containing M(u-C2)M' and M(u-C4)M' units will be synthesized and the magnetic and optical properties will be determined; relationships between 1t backbonding, superexchange efficiency, magneticand electronic properties will also be probed and compared to those of the building blocks. This fundamental structure-property relationship information will assist our understanding of factors necessary for engineering cyano- and acetylido-based clusters with tunable magnetic and optical properties. Fundamental issues concerning how substitution of transition metal centers into rectangular cluster archetypes impact resulting optical and magnetic properties will be investigated. Insertion of anisotropic spin centers interact and contribute to the magnetic ground state, impact magnetic exchange, effective barrier heights, and quantum magnetization tunnelling will be probed in these rectangular clusters. Photomagnetic clusters will be prepared and fundamental magnetic bistability and optical intramolecular electron transfer processes probed via several active collaborations. Proposed Nanoscale Institute (lecture/lab, NUE:SI@UK) and Physical property measurement summer short courses will enable students, mentors, and teachers to discover fundamental aspects of nanoscale science and obtain skills concerning several spectroscopic characterization methods via active learning and hands-on training techniques; first-principles discovery and explanation of observed properties in lecture and laboratory settings will be emphasized. Active recruitment and support of regional students from Centre College and Kentucky State University (KSU, only state HBCU) in research activities is also proposed. Broader Impact. Proposed Summer Nanoscale Institute (lecture/lab) and Physical property measurement courses with hands-on training and using active learning techniques will introduce and describe nanoscale science and spectroscopy concepts from a first-principle standpoint. Spectroscopic and magnetic characterization of user-supplied materials, will be discussed (via lectures), and tutorial experiments performed by students (undergraduate, graduate, and postdoctoral). These tutorials will be digitized and made available via the internet, as downloadable QuickTime video segments; short quizzes and interactive DVDs will accompany each module. Intellectual development and technical training of scientists at several institutions to use a variety of spectroscopic and magnetic characterization techniques is anticipated. Upon successful completion of the course students will become registered users of equipment and bring their newly acquired expertise back to their home institutions; these students will be given priority in UK Chemistry graduate recruitment. Collaborative participation of mentors and exchange and support of students in proposed research activities from surrounding minority serving and HBCU institutions should expand nanoscale curriculum development and research activities across the region. Acquired skills and access to spectroscopic instrumentation will enable timely and cost-effective collection and interpretation of spectroscopic data for research groups at a variety of regional undergraduate institutions; increased productivity and expansion of existing science and materials programs currently lacking instrumentation and/or expertise may also be realized. Ideally more scholarship, publications, and grant applications will result and thus significantly improve federal funding prospects for participating researchers and institutions across the region.