Platinum-Conjugated Homo- and Heterobichromophoric Complexes of Tetracene and Pentacene

Homobichromophoric platinum­(II) complexes containing tetracenyl rings (T-Pt-T) and pentacenyl rings (P-Pt-P) were synthesized by Sonogashira coupling between trans-[Pt­(PEt3)2I2] and 5-ethynyl-12-[(triisopropylsilyl)­ethynyl]­tetracene (T-SiH) and 6-ethynyl-13-[(triisopropylsilyl)­ethynyl]­pentacene (P-SiH), respectively. A heterobichromophoric complex consisting of tetracenyl and pentacenyl rings (T-Pt-P) was generated by coupling P-SiH and platinated T-SiH. The homobichromophoric complexes were characterized by single-crystal X-ray diffraction. The electronic absorption and emission spectra of the complexes were investigated. All the complexes displayed acene-based fluorescence. The emission spectrum of T-Pt-P showed dual emissions of the tetracenyl and pentacenyl rings. Monitoring the pentacenyl emission gave an excitation spectrum which resembled the absorption spectrum, suggesting the presence of intramolecular energy transfer from the singlet excited state of the tetracenyl ring to the singlet excited state of the pentacenyl ring.