An investigation on the second-order NLO properties of novel cationic cyclometallated Ir(III) complexes of the type [Ir(2-phenylpyridine)2(9-R-4,5-diazafluorene)]+ (R = H, fulleridene) and the related neutral complex with the new 9-fulleriden-4-monoazafluorene ligand

Fullerene-functionalized novel cationic cyclometalated Ir(III) complexes [Ir(ppy)2(N-N)]X and [Ir(ppy)2(C-N)] (Hppy = 2-phenylpyridine, N-N = 4,5-diazafluorene, 9-fullerenylene-4,5-diazafluorene; HC-N = 9-fullerenylene-4-azafluorene; X = PF6-, C12H25SO3-) bearing diaza- or cyclometalated monoazafluorene ligands, substituted with a C60-fullerene moiety at 9-position, were prepd. by reaction of [Ir2Cl2(ppy)4] with the corresponding azafluorene ligands. All complexes show a neg. large value of μβ1907 (-600 to -2190 × 10-48 esu), as detd. by the Elec. Field Induced Second Harmonic generation (EFISH) technique working at 1.907 μm in 10-3 M CH2Cl2 soln. The NLO response increases upon introduction of the fullerene moiety, due to a decrease of the interaction forces between the anion and cation within the ion pair which leads to an increase of the percentage of free ions, as evidenced by diffusion NMR expts. Besides, it appeared that for the neutral complex [Ir(ppy)2(9-fullerenylene-4-monoazafluorene)] the EFISH μβ1907 value is lower than that of cationic Ir(III) complexes, but comparable or slightly lower to the values of other neutral Ir(III) complexes such as [Ir(ppy)2(RCOCR'COR)] (R = Me, Ph; R' = H, 2,4-dinitrophenyl), confirming that the second-order NLO response of these neutral chromophores is dominated by ILCT processes concerning cyclometalated 2-phenylpyridines.