Manipulating Spin States, Spin Transmission, and Charge Transfer Using Optical and Electrical Fields

Abstract

Spin manipulation is fundamental for molecular spintronics and many quantum devices, and provides new opportunities for computation, communication, and sensing. Manipulating spins with methodologies other than modulation of an external magnetic field provides opportunities for further device miniaturization, with applied optical and electrical fields offering possible approaches. For spintronic and quantum applications, molecules feature advantages including the possibility to highly polarize spins at room temperature, and facile mass production at high fidelity.This dissertation focuses on manipulating electron spin and charge distributions in molecules using optical and electrical fields. Key research accomplishments include: (i) a spectroscopical and computational investigation of the impact from expansive conjugation on the excited-state dynamical properties of stable radicals; (ii) the design and synthesis of chiral low-resistance molecular wires with a tripodal anchoring ligand that enforces an ideal orthogonal molecular organization and optimally dense packing of self-assembled monolayers (SAMs) formed on metal and semiconductor surfaces, and studying the generation and propagation of spin-polarized currents enabled by the chirality-induced spin selectivity (CISS) effect; and (iii) determining the driving force dependence of ultrafast intramolecular proton-coupled electron transfer (PCET) and establishing new mechanistic insights for such reactions. Spin state generation, spin transmission, and electron transfer induced by optical and electrical fields were interrogated on a wide range of molecular systems. Structure-function relationships revealed by this dissertation will facilitate molecular designs with exceptional optical, electrical, and magnetic properties for electronic, spintronic, and quantum information science (QIS) applications.