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-br omomethylanthracene with cyclopentadienylsodium and transformed into its th allium(I) derivative on reaction with thallium ethoxide 3. The 9-anthrylmet hylcyclopentadienyl (AnCH(2)C(5)H(4)) derivatives of rhodium(I) and iridium (I) of formula [M(eta(5)-AnCH(2)C(5)H(4))L-2] (M = Rh or Ir; L = C2H4, CO, PPh3, C8H14; L-2=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(eta(5)-AnCH(2)C(5)H(4))(eta(2)-C2H4)(2)] (4) and [Rh(eta(5)-AnCH(2 )C(5)H(4))(CO)(2)] (5) react with triphenylphosphine, at 130 degrees C to g ive [Rh(eta(5)-AnCH(2)C(5)H(4))(eta(2)-C2H4)(PPh3)] (7) and [Rh(eta(5)-AnCH (2)C(5)H(4))(CO)(PPh3)] (8). All complexes were characterised by elemental analysis, mass spectrometry, H-1-NMR and FTIR. The structures of two of the m, i.e. [Rh(eta(5)-AnCH(2)C(5)H(4))(eta(2)-C2H4)(2)] (4) and [Rh(eta(5)-AnC H(2)C(5)H(4))(CO)(2)] (5), were elucidated by single crystal X-ray diffract ion. Compound 4 crystallises in the triclinic space group P (1) over bar wi th a = 11.112(1), b = 12.065(1), c = 15.982(2) Angstrom; alpha = 99.83(1), beta = 107.86(1), gamma = 107.22(1)degrees. V = 1865.6(3) Angstrom(3). Z = 4, D-calc = 1.475 g cm(-1), R-1 = 0.0414 [I > 2 sigma(I)], wR(2) = 0.0953. Compound 5 crystallises in the triclinic space group P (1) over bar with a = 12.232(1), b = 13.463(1), c = 13.488(1) Angstrom; alpha = 61.25(1), beta = 68.51(1), gamma = 67.45(1)degrees. V = 1752.5(2) Angstrom(3). Z = 4, D-ca lc = 1.570 g cm(-1), R-1 = 0.0313 [I > 2 sigma(I)], wR(2) = 0.0795. The UV- vis spectra (280-700 nm) of I and of complexes 4-11 were recorded. The spec tra 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 simil ar fluorescence spectra which are typical of the anthrylic fluorophore but have extremely low intensity (the one observed for 9-methyranthracene was b elow 5% and taken as the reference compound). The mechanism of fluorescence quenching in the complexes 4-11 is discussed. (C) 2000 Elsevier Science S. A. All rights reserved.