Catalytic Synthesis of Donor-Acceptor-Donor (D-A-D) and Donor-Acceptor-Acceptor (D-A-A) Pyrimidine-Ferrocenes via Acceptorless Dehydrogenative Coupling: Synthesis, Structures, and Electronic Communication

Abstract

The synthesis and full characterization of a series of ferrocene-decorated pyrimidines with donor-acceptor-donor (D-A-D) and donor-acceptor-acceptor (D-A-A) architectures are reported. The three novel compounds share a pyrimidine core and single ferrocenyl donor arm, with an additional substituent varied from donor ferrocene (1) to acceptor pyrenyl (2) to donor (4-diphenylamino)phenyl groups (3). The compounds could be easily constructed in acceptable yields in one-pot reactions via acceptorless dehydrogenative coupling reactions mediated by a ruthenium coordination complex supported by a simple bidentate P^N ligand. The solution and solid-state structures of the new pyrimidines are described along with photophysical and computational characterization. The lack of near IR (NIR) transitions upon single-electron oxidation of the compounds implies that the pyrimidinyl unit is less effective at mediating electronic communication compared with pyridine or pyrrole cores. Nevertheless, strong absorption in the far visible and NIR is observed upon formation of a dicationic species from 3 and is attributed to efficient charge transfer from the pyrimidine core to the oxidized donor units.