Synthesis and characterization of cruciform-conjugated molecules based on tetrathiafulvalene

Stepwise acetylenic scaffolding provides cruciform-conjugated molecules with vertically disposed pi-systems, one being an extended tetrathiafulvene (TTF) unit. Two synthetic routes for a cruciform dimer incorporating a total of two extended TTFs was developed, employing either an oxidative Hay coupling reaction as the final dimerization step or as one of the initial steps. Both routes take advantage of ready access to new mono- and diethynylbenzene building blocks incorporating a variety of other functionalitites. The redox and optical properties of the cruciform molecules were investigated by cyclic and differential pulse voltammetries and UV-vis absorption spectroscopy. The access to multiple redox states renders the molecules attractive candidates as wires, or possibly transistors, for molecular electronics. Generation of a quinoid structure by oxidation is supported by density functional theory calculations.