KSEF R&D Excellence: Molecule-Based Magnetic Clusters Constructed from Poly(pyrazolyl) borate Acetylide and Butadiynylide Building Blocks

Acetylide (C2R) and 1,3-butadiynyl (C2R) complexes and clusters are expected to exhibit properties that are markedly different than cyanometalates. Several new and robust alkynyl complexes (building blocks) will be prepared and characterized via structural, magnetic, and spectroscopic techniques. Rectangular clusters containing M(,u-l,2-C2)M' and M(u-l,4-C4)M' units will be synthesized and the structures, magnetic, and optical properties will be investigated via active collaborations with an international team of theoreticians, crystallographic, and magnetism experts. Structure-property relationships will be drawn and will assist our understanding of the factors necessary for engineering alkynyl-based clusters with tunable magnetic and optical properties. We propose to: (1) prepare several poly(pyrazolyl)borate polyacetylide complexes (building blocks) and (2) investigate their controlled aggregation into well-defined magnetic clusters using a building block synthetic approach. Aggregation of these centers via treatment of the [(Tp*)- Mn(C£R3)3](n-4) (ER3 = SiMe3, SnBu3) complexes with stoichiometric equivalents of MnXnLm (X = Cl, Br; L = bipy, Tp, etc.) should afford M(Cn)M' linkages in a controllable manner. Relationships between 7t backbonding, superexchange efficiency, magnetic-, and electronic properties will be determined for a series of structurally related magnetic cluster compounds, initially containing 3d metal ions; subsequent investigations will be expanded to include 4d and 5d centers as these should also contribute significant spin state (zero-field splitting, D) and orbital anisotropy (spin-orbit coupling, A) to the cluster magnetic ground state. Questions concerning how these anisotropic spin centers interact and contribute to the magnetic ground state, impact magnetic exchange, effective barrier heights, and quantum magnetization tunneling will be investigated for a series of rectangular clusters. Data storage devices constructed from these magnetic clusters may ultimately afford several patents and a start-up company within the Commonwealth.