Selective Synthesis and Photophysical Properties of Phosphorescent Heteroleptic Iridium(III) Complexes with Two Different Bidentate Groups and Two Different Monodentate Ligands

Rational synthetic procedures for the preparation of phosphorescent heteroleptic iridium­(III) complexes, with controlled stereochemistry, of general formula IrX­{κ2-N,C-(qui-C6H4)}­(acac)­(PiPr3) and their photophysical properties are reported. The d4 pentahydride IrH5(PiPr3)2 (1) promotes the chelate-supported C–H bond activation of 2-phenylquinoline to give IrH2{κ2-N,C-(qui-C6H4)}­(PiPr3)2 (2), which affords the five-coordinate monohydride [IrH­{κ2-N,C-(qui-C6H4)}­(PiPr3)2]­BF4 (3) by protonation with HBF4. Treatment of 3 with potassium acetylacetonate (Kacac) yields the hydrido target compound IrH­{κ2-N,C-(qui-C6H4)}­(acac)­(PiPr3) (4). Phenylacetylene and acetylene insert into the Ir–H bond of 3 to form the five-coordinate alkenyl derivatives [Ir­((E)-CHCHR)­{κ2-N,C-(qui-C6H4)}­(PiPr3)2]­BF4 (R = Ph (5), H (6)). Similarly to 3, complexes 5 and 6 react with K­(acac) to give Ir­((E)-CHCHR)­{κ2-N,C-(qui-C6H4)}­(acac)­(PiPr3) (R = Ph (7), H (8)). The chloride counterpart of 4, 7, and 8 has been obtained by starting from IrCl3(tht)3 (9; tht = tetrahydrotiophene). Treatment of this compound with triisopropylphosphine and 2-phenylquinoline leads to the five-coordinate species IrCl2{κ2-N,C-(qui-C6H4)}­(PiPr3) (10). The use of triphenylphosphine instead of triisopropylphosphine affords the PPh3 analogue IrCl2{κ2-N,C-(qui-C6H4)}­(PPh3) (11). Complexes 10 and 11 react with K­(acac) to give IrCl­{κ2-N,C-(qui-C6H4)}­(acac)­(PR3) (PR3 = PiPr3 (12), PPh3 (13)). The six-coordinate compounds 4, 7, 8, 12, and 13 are yellow-orange emissive upon photoexcitation, with short lifetimes and quantum yields increasing in the sequence 7 (CHCHPh) 12 (Cl) 8 (CHCH2) 4 (H), as the contribution of the metal center to the HOMO of the complexes also increases.

本研究报道了通式为IrX{κ2-N,C-(qui-C6H4)}(乙酰丙酮根(acac))(三异丙基膦(PiPr3))、具有可控立体化学的磷光异配体铱(III)配合物的合理合成路线，及其光物理性质。d⁴构型五氢化物IrH5(PiPr3)2（化合物1）可介导2-苯基喹啉的螯合辅助C-H键活化，得到IrH2{κ2-N,C-(qui-C6H4)}(PiPr3)2（化合物2）；该化合物经四氟硼酸(HBF4)质子化，得到五配位单氢化物配合物[IrH{κ2-N,C-(qui-C6H4)}(PiPr3)2]BF4（化合物3）。将化合物3与乙酰丙酮钾(Kacac)反应，可得到氢化物目标产物IrH{κ2-N,C-(qui-C6H4)}(acac)(PiPr3)（化合物4）。苯乙炔与乙炔可分别插入化合物3的Ir-H键中，得到五配位烯基衍生物[Ir((E)-CH=CHR){κ2-N,C-(qui-C6H4)}(PiPr3)2]BF4（R=苯基(Ph)时为化合物5，R=氢(H)时为化合物6）。与化合物3类似，配合物5和6分别与乙酰丙酮钾(Kacac)反应，得到Ir((E)-CH=CHR){κ2-N,C-(qui-C6H4)}(acac)(PiPr3)（R=Ph时为化合物7，R=H时为化合物8）。化合物4、7、8的氯化物类似物可通过三(四氢噻吩)合氯化铱(III)（IrCl3(tht)3，tht=四氢噻吩(tetrahydrothiophene)）为起始原料制得。将该化合物与三异丙基膦和2-苯基喹啉反应，可得到五配位配合物IrCl2{κ2-N,C-(qui-C6H4)}(PiPr3)（化合物10）。以三苯基膦(PPh3)替代三异丙基膦进行上述反应，可得到对应三苯基膦配合物IrCl2{κ2-N,C-(qui-C6H4)}(PPh3)（化合物11）。配合物10和11分别与乙酰丙酮钾(Kacac)反应，得到IrCl{κ2-N,C-(qui-C6H4)}(acac)(PR3)（PR3=PiPr3时为化合物12，PR3=PPh3时为化合物13）。化合物4、7、8、12和13均为六配位配合物，经光激发后可发射黄橙色光；其发光寿命较短，量子产率按7（CH=CHPh）<12（Cl）<8（CH=CH2）<4（H）的顺序依次升高，这与金属中心对配合物最高占据分子轨道(HOMO, Highest Occupied Molecular Orbital)的贡献逐渐增大相一致。