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

σ-Metalation of tetracene can change the emission color of and introduce new structural dimensionality to the organic chromophore. Two synthetic entries to σ-metallotetracenes have been explored, leading to emissive mononuclear (Ph3PAuI)-tetracene (1) and cis-[Br(Et3P)2PtII]-tetracene (2) and binuclear (R3PAuI)2-tetracenyldiacetylide (R = Ph (4), Me (5)) and trans-[I(Et3P)2PtII]2-tetracenyldiacetylide (6). Metalation can lower the emission energy of tetracene up to 0.53 eV. The X(Et3P)2PtII group (X = Br, I) has stronger perturbations on the tetracenyl ring than the R3PAuI group. σ-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 AuI chains. In contrast to the other complexes, the crystal of 5 is not emissive, possibly due to efficient exciton delocalization.