Effect of acetylenic chain length on the tuning of functional properties in fluorene-bridged polymetallaynes and their molecular model compounds

Li Liu, Wai Yeung Wong, Suk Yue Poon, Jian Xin Shi, Kok Wai Cheah, Zhenyang Lin

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We describe for the first time thermally stable and high-molecular-weight group 10 platinum(II) and group 12 mercury(II) polyyne polymers consisting of 2,7-bis(buta-1,3-diynyl)-9,9-dihexylfluorene linking units trans-[- Pt(PBu 3)2(C≡C)2R(C≡C)2-] n and [-Hg(C≡C)2R(C≡C)2-] n (R = 9,9-dihexylfluorene-2,7-diyl). The optical absorption and photoluminescence spectra of these carbon-rich metallopolymers were examined and compared with their dinuclear model complexes trans-[Pt(Ph)(PEt 3)2(C≡C)2R-(C≡C) 2Pt(Ph)(PEt3)2] and [MeHg(C≡C) 2R(C≡C)2HgMe] as well as the group 11 gold(I) congener [(PPh3)-Au(C≡C)2R(C≡C) 2Au(PPh3)]. The regiochemical structures of the polymers were studied by NMR spectroscopy and ascertained by single-crystal X-ray structural analysis for the model platinum(II) compound. The heavy-atom effects of group 10-12 transition metals in triplet light energy harvesting and the influence of the C≡C chain length on the spatial extent of singlet and triplet excitons in metalated systems of the form [-M(C≡C) mR(C≡C)mM-]n (M = Pt, Au, or Hg chromophore; m = 1, 2) are systematically characterized. The dependence of the optical energy gap as a function of the acetylenic chain length for the platinum system was probed by both optical methods and molecular orbital calculations, and a linear correlation was derived between the highest occupied molecular orbital-lowest unoccupied molecular orbital gap and 1/m2. An extension of the C≡C unit gives rise to a state of lower triplet energy and is accompanied by a decrease in the triplet quantum yield and lifetime, in accordance with the energy gap law for the triplet states in metal polyynes.
Original languageEnglish
Pages (from-to)1369-1378
Number of pages10
JournalChemistry of Materials
Issue number5
Publication statusPublished - 7 Mar 2006
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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