Improved Bipolar Properties of Ester-Functionalized Discotic Diimine-Dithiolene Complexes

A series of platinum diimine-dithiolene complexes with a 5,6-dihydro-1,4-dithiin-2,3-dithiolato (dddt2-) dithiolene ligand and a bipyridine carrying tris-alkoxyphenyl fragments connected through an ester linker (bpyCn, n=8, 12, 16, 10(s), 20) (Scheme 1) has been developed. The mesomorphic properties of the ligands and of the platinum complexes have been investigated by a combination of DSC, POM and SAXS analyses. The platinum complexes were found to self-organize into columnar mesophases of hexagonal symmetry over large temperature range including room temperature. Their electronic properties were also characterized by a combination of electrochemistry, absorption and emission spectroscopy measurements and TD-DFT calculations. Besides being liquid crystalline, these compounds can undergo two oxidation processes and two reduction processes in a fully reversible manner, allowing the isolation of stable dicationic and dianionic species. Such a behavior is highly promising for the development of ambipolar semiconducting soft materials. A series of ester-functionalized platinum-diimine-dithiolene complexes exhibiting two successive reversible reduction processes and two successive reversible oxidation processes can self-organize into room temperature columnar mesophases.image