Synthesis of 9-anthrylmethyl-functionalised cyclopentadienyl derivatives of rhodium(I) and iridium(I) and study of their luminescence properties

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(h5-AnCH2C5H4)L2] (MRh or Ir; LC2H4, CO, PPh3, C8H14; L2C7H8, 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(h5-AnCH2C5H4)(h2-C2H4)2] (4) and [Rh(h5-AnCH2C5H4)(CO)2] (5) react with triphenylphosphine, at 130°C to give [Rh(h5-AnCH2C5H4)(h2-C2H4)(PPh3)] (7) and [Rh(h5-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(h5-AnCH2C5H4)(h2-C2H4)2] (4) and [Rh(h5-AnCH2C5H4)(CO)2] (5), were elucidated by single crystal X-ray diffraction. Compound 4 crystallises in the triclinic space group P1( with a11.112(1), b12.065(1), c15.982(2) A, ; a99.83(1), b107.86(1), g107.22(1)°. V1865.6(3) A, 3. Z4, Dcalc1.475 g cm1, R10.0414 [I\2s(I)], wR20.0953. Compound 5 crystallises in the triclinic space group P1( with a12.232(1), b13.463(1), c13.488(1) A, ; a61.25(1), b68.51(1), g67.45(1)°. V1752.5(2) A, 3. Z4, Dcalc1.570 g cm1, R10.0313 [I\2s(I)], wR20.0795. 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. © 2000 Elsevier Science S.A. All rights reserved.