Synthesis and characterization of facial and meridional tris-cyclometalated iridium(III) complexes.

作者: Arnold B. Tamayo , Bert D. Alleyne , Peter I. Djurovich , Sergey Lamansky , Irina Tsyba

DOI: 10.1021/JA034537Z

关键词:

摘要: The synthesis, structures, electrochemistry, and photophysics of a series facial (fac) meridional (mer) tris-cyclometalated Ir(III) complexes are reported. have the general formula Ir(C'N)(3) [where C'N is monoanionic cyclometalating ligand; 2-phenylpyridyl (ppy), 2-(p-tolyl)pyridyl (tpy), 2-(4,6-difluorophenyl)pyridyl (46dfppy), 1-phenylpyrazolyl (ppz), 1-(4,6-difluorophenyl)pyrazolyl (46dfppz), or 1-(4-trifluoromethylphenyl)pyrazolyl (tfmppz)]. Reaction dichloro-bridged dimers [(C'N(2)Ir(mu-Cl)(2)Ir(C'N)(2)] with 2 equiv HC( wedge )N at 140-150 degrees C forms corresponding isomer, while higher reaction temperatures give predominantly isomer. Both isomers can be obtained in good yield (>70%). isomer Ir(tpy)(3) Ir(ppz)(3) Ir(tfmppz)(3) been structurally characterized using X-ray crystallography. near identical bond lengths (av Ir-C = 2.018 A, av Ir-N 2.123 A) angles. three expected length alternations for differing trans influences phenyl pyridyl/pyrazolyl ligands. Bonds that to groups longer (Ir-C 2.071 2.031 than when they heterocyclic groups. bonds N C, respectively, very similar those observed isomers. DFT calculations both singlet (ground) triplet states compounds suggest HOMO levels mixture Ir ligand orbitals, LUMO ligand-based. All show reversible oxidation between 0.3 0.8 V, versus Fc/Fc(+). easier oxidize by ca. 50-100 mV. phenylpyridyl-based reduction potentials -2.5 -2.8 whereas phenylpyrazolyl-based exhibit no up solvent limit -3.0 V. intense absorption bands UV region assigned into (1)(pi --> pi) transitions weaker MLCT (metal-to-ligand charge transfer) extend visible region. pyrazolyl-based hypsochromically shifted relative pyridyl-based compounds. tris-cyclometalates emission room temperature 77 K, derivatives emit strongly only K. energies lifetimes (450-550 nm, 2-6 micros) (390-440 14-33 characteristic mixed ligand-centered/MLCT excited state. pyridyl cyclometalates markedly different spectroscopic properties do forms. Isolated samples mer-Ir(C( )N)(3) thermally photochemically converted forms, indicating kinetically favored products. lower thermodynamic stabilities likely related structural features these complexes; is, configuration places influencing opposite each other, all pyrazolyl complexes. strong influence leads observation oxidize, broad, red-shifted emission, quantum efficiencies their counterparts.

参考文章(0)