Sequence-Specific Synthesis of Platinum-Conjugated Trichromophoric Energy Cascades of Anthracene, Tetracene, and Pentacene and Fluorescent “Black Chromophores”

A sequence-specific synthesis of trichromophoric energy cascades containing anthracenyl (A), tetracenyl (T), or pentacenyl (P) rings is achieved by coupling Pt-II ions and singly desilylated bis(triisopropylsilylethynyl)acenes (acene = anthracene, tetracene, or pentacene). Four sequences, T-P-T, P-T-P, A-P-T, and A-T-P, are generated. Absorption spectra of the triads show intense bands due to the S-0 -> S-1 transitions of the acenes. The A-P-T and A-T-P, being able to absorb strongly throughout the entire visible region, are rare examples of "black chromophores". Different sequences are shown to have different emission fingerprints. Emission spectra of A-P-T and A-T-P show that excitation at the S-0 -> S-1 band of A gives rise to emissions from the S-1 excited states of A, T, and P, implying the presence of energy transfer from the excited state of A to those of T and P.