Raul Hernandez Sanchez

Electronic structure manipulation: from inorganic clusters to organic semiconductors

Mixed valence compounds have been recognized over the past five decades as a unique class of chemical compounds. Their distinctive spectral, electrochemical, physical and magnetic properties arise from electron delocalization into the sites with uneven valence. A primary consequence of this electron delocalization phenomena is the acquisition and stabilization of high spin multiplicities, as observed in certain dinuclear and polynuclear biological clusters. In the first part of this talk I present the research work that extends the current knowledge on the analysis of synthetic mixed-valent clusters by systematically altering the coordination chemistry and redox states at well-defined synthetic polynuclear iron clusters. We demonstrate that with small variations on the solvation coordination sphere and redox state, one can transverse spin ground states from S = 0 to S = 11 at the same polynuclear species.

While manipulation of the electron-electron interaction can result in unprecedented thermally stable spin multiplicities, it can also guide the design of molecules with high performance electrochemical properties for applications in batteries. Next, I show the use of macromolecular platforms as the active electrolytes for stable battery cycling operation in organic media with negligible calendar fade and with coulombic efficiencies exceeding 99.95%. The cell stability demonstrated here approaches the level necessary for a long lifetime nonaqueous redox flow battery. Last, I will introduce our work on a new type of electronic material made from the self-assembly of a molecular semiconductor that is shaped like a capsule forming permanently porous semiconducting films. The capsule interior volume is ~415 ų. This hollow material is able to form the active layer in field effect transistor devices. These devices are remarkable in their ability to distinguish, through their electrical response, between small structural differences in the guest.