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.