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University of Kentucky Acetylide and butadiynylide complexes, clusters, and networks are a relatively unexplored class of inorganic materials that exhibit properties unlike those found for other materials. Rigid-rod metal acetylides have attracted considerable attention as potential materials for use in non-linear optical, luminescent, redox-active components, and as molecular wire interconnects in electronic devices and sensors. These so-called carbon wires efficiently couple transition metal centers both electronically and magnetically, offering the prospect of tuning the redox and superexchange pathway efficiency with angstrom level precision. As part of continuing effort to prepare discrete magnetic clusters, we have recently turned our attention towards a fundamentally different building block: poly(pyrazlolyl)borate acetylides and butadiynylides. Dinuclear complexes containing paramagnetic transition metal centers linked by buta¬diynylides have been reported. Surprisingly the C4-linked paramagnetic Fe and Mn centers afford diamagnetic clusters at 300 K suggesting that very efficient superexchange interactions that are much more efficient than those observed for M-CN-M (M = Fe, Mn) units and Cn-based clusters are expected to retain their magnetic properties at higher temperatures; {Pt(C4)Pt}4 rectangles have recently been reported. If this is a general phenomenon, it may be possible to construct a series of polynuclear magnetic complexes where paramagnetic metal centers are linked via acetylide (C2) and butadiynylide (C4) bridges that are capped with pyrazolylborate ligands. We propose to: (1) prepare several poly(pyrazolyl)borate polyacetylide complexes (building blocks) and (2) investigate the controlled aggregation of these precursors into well-defined magnetic clusters using a building block synthetic approach. Aggregation of these centers via treatment of the [TpM(n)(C2ER3)3](n-4) (E = Si, Sn) with a series of M(n)X(n)L(m) (X = Cl, Br, F; L = bipy, Tp) complexes should afford M(Cn)M linkages in a controllable manner. Relationships between ? backbonding, superexchange efficiency, magnetic-, and electronic properties will be determined for a series of structurally related compounds. Such information may ultimately lead to materials with tunable magnetic, electrical, and optical properties that persist at high temperatures.
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