The Chemical Synthesis Program of the Chemistry Division supports the project by Professor Gladysz. Professor Gladysz is a faculty member in the Department of Chemistry at Texas A&M University and is developing novel gyroscope-like metal complexes. Macroscopic gyroscopes serve as devices for sensing and/or maintaining the orientation of an object (e.g., space stations; torpedo warheads; virtual reality headsets; mobile phone displays; drones; flying insects via biological assemblies termed "halteres"). The classic mechanical gyroscope, encountered by many as a childhood toy, consists of an axle, a flywheel that can rotate, and a protective housing. When the object is displaced from its axis of rotation, there is a restoring force arising from the conservation of angular momentum. The underlying physics holds at the molecular level, allowing chemists to pursue the limit of gyroscope miniaturization. This project is directed at the synthesis of molecular gyroscopes that contain a metal based flywheel contained in a novel cage-like structure anchored by two phosphorus atoms that are 180° apart. The ease of rotation of the flywheel is maximized, and the demonstration of gyroscopic properties sought. These systems are linked to give "gearboxes", and investigated as catalysts for fine and commodity chemical syntheses, for which metals are commonly required. Since the metals are confined to a restricted space, it is hoped that new selectivities based upon reactant or product size or shape can be realized. This project focuses on the synthesis, fundamental structural and dynamic properties, reactivity, and applications (molecular devices, catalysis) of gyroscope-like metal based molecular rotors. These most commonly feature a trans-diphosphine ligand in which the phosphorus atoms are spanned by three chains, usually of the formula (CH2)n (n > 10) but also incorporating hetero-atoms, p-phenylene groups, or other functionalities. They are accessed by three-fold intramolecu-lar ring closing metatheses of precursors of the type trans-LyM(P((CH2)mCH=CH2)3)2, followed by C=C hydrogenation (n = 2m+2). The coordination geometry may be square planar, trigonal bipyramidal, or octahedral (y = 2-4). If the ligands (Ly) are sufficiently small relative the (CH2)n linkages, the LyM unit may rotate within the gyroscope cage. Arrays of gyroscope like units with parallel axes are synthesized with spacings that allow the rotators to interact, enforcing correlated motion such as in gearboxes or waterwheels. The metal fragments are extruded from the gyroscope cages, providing a heretofore unknown class of macrocyclic dibridgehead diphosphines. These are independently synthesized, combined with various metal species to form new gyroscope-like complexes, and (in view of their ability to turn themselves "inside out") investigated as "transport containers" for toxic or harmful metal species.
