The compound 9-anthrylmethylcyclopentadiene 1 was prepared by reacting 9-bromomethylanthracene with cyclopentadienylsodium and transformed into its thallium(I) derivative on reaction with thallium ethoxide 3. The 9-anthrylmethylcyclopentadienyl (AnCH2C5H4) derivatives of rhodium(I) and iridium(I) of formula [M(η5-AnCH2C5H4)L2] (M=Rh or Ir; L=C2H4, CO, PPh3, C8H14; L2=C7H8, 1,5-C8H12) 4-6 and 9-11 were obtained in good yields by reacting the corresponding rhodium(I) and iridium(I) chlorides with 3. Both [Rh(η5-AnCH2C5H4)(η2-C2H4)2] (4) and [Rh(η5-AnCH2C5H4)(CO)2] (5) react with triphenylphosphine, at 130°C to give [Rh(η5-AnCH2C5H4)(η2-C2H4)(PPh3)] (7) and [Rh(η5-AnCH2C5H4)(CO)(PPh3)] (8). All complexes were characterised by elemental analysis, mass spectrometry, 1H-NMR and FTIR. The structures of two of them, i.e. [Rh(η5-AnCH2C5H4)(η2-C2H4)2] (4) and [Rh(η5-AnCH2C5H4)(CO)2] (5), were elucidated by single crystal X-ray diffraction. Compound 4 crystallises in the triclinic space group P1̄ with a=11.112(1), b=12.065(1), c=15.982(2) Å; α=99.83(1), β=107.86(1), γ=107.22(1)°. V=1865.6(3) Å3. Z=4, Dcalc=1.475 g cm-1, R1=0.0414 [I>2σ(I)], wR2=0.0953. Compound 5 crystallises in the triclinic space group P1̄ with a=12.232(1), b=13.463(1), c=13.488(1) Å; α=61.25(1), β=68.51(1), γ=67.45(1)°. V=1752.5(2) Å3. Z=4, Dcalc=1.570 g cm-1, R1=0.0313 [I>2σ(I)], wR2=0.0795. The UV-vis spectra (280-700 nm) of 1 and of complexes 4-11 were recorded. The spectra of 4-11 are indicative of important interactions between the anthrylic chromophore and the cyclopentadienyl-metal moiety. When excited at 365 nm, 1 results to be an efficient light-emitting molecule, while its derivatives 4-11 are poorly luminescent compounds. Indeed, all complexes exhibit similar fluorescence spectra which are typical of the anthrylic fluorophore but have extremely low intensity (the one observed for 9-methylanthracene was below 5% and taken as the reference compound). The mechanism of fluorescence quenching in the complexes 4-11 is discussed.
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