Heterocycles and their derivatives have long been of interest for use in advanced electronic applications. Due to their unique properties including environmental stability, high processibility, and low production cost, organic-based electronic materials are an attractive alternative to conventional inorganic semiconductors. Specifically, thiophenes, furans, and pyridazines (6-membered aromatic rings containing two adjacent nitrogen atoms) represent alluring building blocks for electronic materials due to their ease of synthesis and stability. In addition, while oxazines (6-membered rings with an adjacent oxygen and nitrogen) have been utilized for their medicinal properties, they also possess interesting redox and optical properties. Polymers and discrete molecules/oligomers incorporating these heterocycles have shown promise in a number of commercial and industrial applications. Our current investigation focuses on the off-metal and transition metal chemistry of thiophenes, furans, pyridazines, and oxazines namely, the formation of fused-ring complexes bound η5 to a metal through a Cp moiety. By including a transition metal into fused-heterocycles, we hope to create hybrid materials which blend the synthetic versatility of organics with the novel structural and electronic properties that inorganic moieties possess. For example, formation of the desired complexes, [M(CO)3{η5-1,2-C5H3(1,4-(R)2N2C2}] (M = Mn, Re), was accomplished from a 1,2-diketo precursor, [Mη5-1,2-C5H3(COR)2}(CO)3] (R= 4-ClPh, 4-MeOPh, 5-BrTp). Reaction of these 1,2-diketo complexes with excess hydrazine under mild conditions (room temperature) afforded the desired pyridazine complexes in good yield (60-83%). These complexes display high solid state stability in air and relatively good stability in solution. Additionally, computational studies were performed on both these on- and off-metal heterocycles, including electrostatic potential (ESP) mapping and Natural Bonding Orbital (NBO) modeling. Comparative computational studies between oxazine- and pyridazines-based materials show that the pyridazines display better electronic properties for Non-Linear Optical (NLO) applications. Electrochemical polymerization of the free thienyl pyridazine ligand and corresponding organometallic complex via Cyclic Voltammetry (CV) was accomplished as well, affording redox stable thin films. CV studies were also performed on a number of the other on- and off-metal oxazines, pyridazines, and thiophenes.

Cyclopentadienyl pyridazines, oxazines, and thiophenes and their applications in energy and advanced electronics

ACS Spring Meeting 2021

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