Carbon-rich organometallic materials derived from 4-ethynylphenylferrocene

Using 4-ethynylphenylferrocene (1) as the building block, a new series of rigid-rod alkynylferrocenyl precursors consisting of fluoren-9-one unit, 2-bromo-7-(4-ferrocenylphenylethynyl)fluoren-9-one (2a), 2,7-bis (4-ferrocenylphenylethynyl)fluoren-9-one (2b), 2-trimethylsilylethynyl-7- (4-ferrocenylphenylethynyl)fluoren-9-one (3) and 2-ethynyl-7-(4-ferrocenylphenylethynyl)fluoren-9-one (4) have been prepared in moderate to good yields. The acetylene complex 4 is a useful precursor for the synthesis of well-defined carbon-rich ferrocenyl heterometallic complexes, trans-[(η⁵-C₅ H₅) Fe(η⁵-C₅H₄) C₆ H₄C≡CRC≡CPt(PEt₃) ₂Ph] (5), trans-[(η⁵-C₅ H₅) Fe(η⁵-C₅H₄) C₆ H₄C≡CRC≡CPt(PBu₃) ₂ C≡CRC≡CC₆H₄ (η⁵- C₅H₄)Fe(η⁵ -C₅ H₅)] (6), trans-[(η⁵ -C₅ H₅)Fe(η⁵-C₅ H₄) C₆H₄C≡CRC≡CM(dppm) ₂ Cl] (M=Ru (7), Os (8)) (R=fluoren-9-one-2,7-diyl). All new complexes have been characterized by FTIR, NMR and UV-Vis spectroscopies and fast atom bombardment mass spectrometry (FABMS). The molecular structures of 1, 2a, 4, 6 and 8 have been determined by single-crystal X-ray studies where an iron-iron through-space distance of nanosized dimension (ca. 42 Å) is observed in the trimetallic molecular rod 6. The electronic absorption, luminescence and electrochemical properties of these carbon-rich molecules were investigated and the data were correlated with the theoretical results obtained by the method of density functional theory.