"This project pushes Molecular Electronics (ME) beyond simple distant-dependence studies towards controlling tunneling charge transport with organic synthesis by manipulating the intrinsic properties of organic molecules to shape the tunneling barrier. The measurements will be done with two tools that I have developed; Eutectic Ga-In (EGaIn), which is increasingly being used by the ME community as a robust method for measuring charge-transport through self-assembled monolayers (SAMs) and SAM-templated nanogap (STAN) electrodes, which is a newer tool that allows the facile coupling of light and electric fields into SAM-based tunneling junctions. These tools are critical for performing physical-organic studies in practical tunneling junctions in which the molecules themselves define the smallest dimension of the junction; spectroscopic tools that rely on AFM or STM define the junction with a piezo and are not directly applicable to practical devices, which is the underlying motivation for all research in ME.Two sets of molecules, one cross-conjugated and one combining flexible alkane tails with rigid oligophenylene moieties will be synthesized and investigated; more as necessary. Both series of molecules are designed around straightforward physical-organic studies meant to elucidate structure/property relationships empirically by measuring the influence of systematic structural/electronic changes on the electrical properties of tunneling junctions. The molecules will be incorporated into both EGaIn and STAN junctions to unravel the effects of the energies of the frontier orbitals, dipole moments, and other non-length-dependent synthetic handles. In the STAN junctions, the molecules will be gated with electric fields to examine more closely dynamic shifts in orbital energies and the role of polarizability."