LOW BAND GAP POLYCYCLIC AROMATIC HYDROCARBONS WITH TUNABLE GROUND STATES AND PHYSICAL PROPERTIES

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are two-dimensional (2D) graphite segments, representing one of the most widely investigated compounds both in organic synthetic chemistry and materials science. In general, PAHs exhibit either closed-shell state or open-shell state. Most PAHs are characterized as closed-shell electron configuration, accommodating pi electrons in bonding orbitals. Then open-shell configuration owns one or more unpaired electrons, known as radicals. In this dissertation, we have designed and synthesized two series of open-shell PAHs and two batches of closed-shell PAHs: (1) cyclopenta ring fused bisanthene and its charged species, which turn out to be open-shell singlet diradicals and global aromaticity/anti-aromaticity; (2) curved π-conjugated corannulene dimer diradicaloids that exhibit interesting 3D spin interactions; (3) closed-shell anthracene-fused dibenzo[def,mno]chrysenes with helical structures; (4) bisindeno-annulated bisanthene and dibenzo[def,mno]chrysene, which reveal hugely increased stability. These systems make substantial contributions to open-shell PAHs with unique properties, and contribute complementarily to achieve closed-shell compounds with novel structures.