Synthesis, Electrochemistry, and Photophysical Properties of a Series of Luminescent Pyrene-Thiophene Dyads and the Corresponding Co2(CO)6 Complexes

A series of pyrene based dyad systems together with their dicobalt hexacarbonyl complexes (1b-6b) were synthesized. The pyrene-thiophene dyads are luminescent in room temperature solution with luminescence lifetimes on the nanosecond time scale. At room temperature the dyad emission is quenched by coordination to a Co-2(CO)(6) moiety via an acetylene bridge. However, at 77 K this emission is not fully quenched following complexation. Electrochemical studies suggest that an intraligand state is responsible for the emission. Photochemical studies in the presence of PPh3 indicate that CO loss occurs following broadband irradiation with lambda(exc) > 400 nm, resulting in the formation of both -pentacarbonyl and -tetracarbonyl photoproducts.