Porphyrin Arrays and Perylene Diimide as Molecular Spintronic Components

Abstract

As the shrinking size of silicon-based electronic devices approaches the physical limit hindered by quantum tunneling, molecular electronics has gained attention to be a promising candidate for the development of molecule-size electronics where the individual designed molecules can be assembled to serve the similar functionality of transitional components. In this regard, the introduction of molecular spintronics brings more versatility to superior efficiency in information processing. Spintronic devices sharply contrast with traditional electronics by exploiting the electron spin degree of freedom in addition to the charge and key to the realization of spintronics is elucidating molecular spintronic components. This dissertation illustrates electron spin polarization, propagation, and relaxation behaviors in perylene diimide derivatives, meso-to-meso acetylene-bridged multi[zinc(II) porphyrin] and [copper(II) porphyrin] oligomers. Chapter one discusses a background about molecular spintronics of highly conjugated molecular wires and perylene diimide derivatives, the chiral-induced spin selectivity effect as well as the basics of electron paramagnetic resonance. Chapter two provides the utilization of polyproline-porphyrin complexes as spintronics molecular wires to propagate spin-polarized current measured by spin-dependent Hall devices and mC-AFM. This study demonstrates the importance of employing achiral conjugated wires as low-resistance spintronic wires. Chapter three describes the design of chiral highly conjugated (porphinato)Zn arrays through chirality induction of chiral ligand. The spin polarization and propagation thus can be achieved in the high conductance porphyrinic wires conducted by Hall devices and mC-AFM. In addition, the strategy of ligand exchange in host-guest chemistry enables the opportunity to tune chirality as well spin polarization by replacing enantiomeric ligand in solution, paving the new avenue for the design of chirality-controllable spintronics wires. Chapter four reports the study of aggregation system alanine-based perylene diimide derivatives by conjugation systems through solvent control. By tuning the solubility of solvent, the aggregation can be altered to be nanofibers having orthogonal conjugation systems or nanodonuts having paralleled conjugation systems with the gold electrode. The spin-polarized current was measured in nanodonuts and demonstrate diode-like current-voltage responses. The mechanism may result from asymmetric molecule-electrode coupling. In chapter five, we report spin dynamics in symmetric, strongly π-conjugated bis[(porphinato)copper] (bis[PCu]) systems in which atom-specific macrocycle spin density, porphyrin-to-porphyrin linkage topology, and orbital symmetry play an important role on the magnitudes of electronic spin−spin couplings over substantial Cu−Cu distances.