Synthesis and Luminescence of a Charge-Neutral, Cyclometalated Iridium(III) Complex Containing N∧C∧N- and C∧N∧C-Coordinating Terdentate Ligands

The first examples of iridium(III) complexes containing a terdentate,
N∧C∧N-coordinated 1,3-di(2-pyridyl)benzene derivative, cyclometalated at C2 of the benzene ring, are reported. This mode of
binding becomes significant only if competitive cyclometalation at
C4/C6 is blocked, and the ligand 1,3-di(2-pyridyl)-4,6-dimethylbenzene (dpyxH) has been prepared to achieve this condition.
The charge-neutral complex [Ir(dpyx)(dppy)], 2, (dppyH2 = 2,6-diphenylpyridine) has been isolated, containing dpyx and dppy
bound to the metal through one and two carbon atoms, respectively.
A terpyridyl analogue, [Ir(dpyx)(ttpy)](PF6)2, 3, (ttpy = 4‘-tolylterpyridine) has also been prepared and its X-ray crystal structure
determined, confirming the N∧C∧N binding mode of dpyx.
Complex 2 emits strongly in degassed solution at 295 K (λmax =
585 nm, φ = 0.21, τ = 3900 ns, in CH3CN). In solution, the
excited state can also undergo photodissociation, through cleavage
of one of the Ir−C(dppy) bonds.

首次报道了一类含三齿N∧C∧N配位1,3-二(2-吡啶基)苯衍生物、且在苯环C2位发生环金属化的三价铱配合物。仅当C4/C6位的竞争性环金属化被阻断时，该配位模式才具备显著优势；为此我们合成了配体1,3-二(2-吡啶基)-4,6-二甲基苯（dpyxH）。我们分离得到了中性电荷配合物[Ir(dpyx)(dppy)]（化合物2，其中dppyH₂=2,6-二苯基吡啶），该配合物中dpyx配体通过1个碳原子、dppy配体通过2个碳原子与金属铱配位。此外我们还合成了三联吡啶类似物[Ir(dpyx)(ttpy)](PF₆)₂（化合物3，ttpy=4'-甲基三联吡啶），并通过X射线单晶衍射确定了其晶体结构，证实了dpyx配体的N∧C∧N配位模式。配合物2在295 K的脱气溶液中展现出强发射特性（乙腈溶剂中，最大发射波长λ_max=585 nm，量子产率φ=0.21，荧光寿命τ=3900 ns）。在溶液状态下，其激发态还可通过断裂一条Ir−C(dppy)键发生光解离反应。