Gold(I) and Platinum(II) Tetracenes and Tetracenyldiacetylides: Structural and Fluorescence Color Changes Induced by σ-Metalation

sigma-Metalation of tetracene can change the emission color of and introduce new structural dimensionality to the organic chromophore. Two synthetic entries to sigma-metallotetracenes have been explored, leading to emissive mononuclear (Ph3PAuI)-tetracene (1) and cis-[Br(Et3P)(2)Pt-II]-tetracene (2) and binuclear (R3PAu(I))(2)-tetracenyldiacetylide (R = Ph (4), Me (5)) and trans-[I(Et3P)(2)Pt-II](2)-tetracenyldiacetylide (6). Metalation can lower the emission energy of tetracene up to 0.53 eV. The X(Et3P)(2)Pt-II group (X = Br, I) has stronger perturbations on the tetracenyl ring than the R3PAu(I) group. sigma-Metalation also leads to different crystal packing of the complexes and thus arrangements of the tetracenyl rings. Aurophilic attraction operates in 5, leading to self-assembly of the molecules into a novel honeycomb structure composed of helical Au-I chains. In contrast to the other complexes, the crystal of 5 is not emissive, possibly due to efficient exciton delocalization.