Since their discovery in the early 1960s, metal dithiolenes have engendered significant interest because of their unique electronic and magnetic properties, exhibiting a wide range of oxidation states, coordination geometries, and magnetic moments. Metal dithiolenes have been used in a variety of applications, including conducting and magnetic materials, dyes, non-linear optical materials, and as electroactive substrates in olefin separation methods. Square-planar metal dithiolenes offer the advantage of giving planar molecular materials, which make them attractive building blocks for planar π-conjugated materials, and the integration of transition metals into the conjugated organic backbone offers possibilities for the development of electronic, catalytic, and sensing materials by modifying the optical and electronic properties of the resulting hybrid materials.
In 2009, the Rasmussen group reported the synthesis of a planar π-extended nickel thiophenedithiolene complex, combining the unique aspects of metal dithiolenes with conjugated organic materials. Currently, we have expanded this approach to synthetically modify and tune these planar π-extended metal thiophenedithiolenes by various methods to make functionalized and solution processable thiophenedithiolenes. By varying the transition metal at the dithiolene core, the optical and electrochemical properties of these metal thiophenedithiolenes can be modified. Another method of modifying the thiophenedithiolene is the addition of functional groups, which can both adjust the optical and electronic properties and positively affect the solubility of these oligomers. These small molecules then have the potential as building blocks for π-conjugated materials.
This ability to tune the properties of the metal dithiolenes based on both ligand and transition metal modification will be presented. Transition metals under investigation include nickel, palladium, platinum, gold, and cobalt. Ligand modification includes the addition of various functional groups to tune the optical and electronic properties and alkyl chains to increase the solubility. Polymerization methods will also be discussed. Synthetic details, properties, and characterization of this family of planar π-extended metal thiophenedithiolenes will be presented.