Trapping intermediate MLCT states in low-symmetry {Ru(bpy)} complexes,Chemical Science

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Trapping intermediate MLCT states in low-symmetry {Ru(bpy)} complexes
Chemical Science ( IF 7.6 ) Pub Date : 2017-08-29 00:00:00 , DOI: 10.1039/c7sc02670f
Alejandro Cadranel _{1,

2,

3,

4,

5} , Paola S. Oviedo _{6,

7,

8,

9,

10} , German E. Pieslinger _{6,

7,

8,

9,

10} , Shiori Yamazaki _{11,

12,

13,

14} , Valeria D. Kleiman _{11,

12,

13,

14} , Luis M. Baraldo _{6,

7,

8,

9,

10} , Dirk M. Guldi _{1,

2,

3,

4,

5}

Affiliation

The picosecond excited state dynamics of [Ru(tpm)(bpy)(NCS)]⁺ (RubNCS⁺) and [Ru(tpm)(bpy)(CN)]⁺ (RubCN⁺) (tpm = tris(1-pyrazolyl)methane, bpy = 2,2′-bipyridine) have been analyzed by means of transient absorption measurements and spectroelectrochemistry. Emissive ³MLCTs with (GS)HOMO(h⁺)–(GS)LUMO(e⁻) configurations are the lowest triplet excited states regardless of whether 387 or 505 nm photoexcitation is used. 387 nm photoexcitation yields, after a few picoseconds, the emissive ³MLCTs. In contrast, 505 nm photoexcitation populates an intermediate excited state that we assign as a ³MLCT state, in which the hole sits in a metal-centered orbital of different symmetry, prior to its conversion to the emissive ³MLCTs. The disparities in terms of electronic configuration between the intermediate and the emissive ³MLCTs have two important consequences. On one hand, both states feature very different fingerprint absorptions in transient absorption measurements. On the other hand, the reconfiguration is impeded by a kinetic barrier. As such, the conversion is followed spectroscopically and kinetically on the 300 ps timescale.

中文翻译：

在低对称{Ru（bpy）}络合物中捕获中间MLCT状态

[Ru（tpm）（bpy）（NCS）] ⁺（RubNCS ⁺）和[Ru（tpm）（bpy）（CN）] ⁺（RubCN ⁺）的皮秒激发态动力学（tpm = tris（1- pyrazolyl）甲烷，bpy = 2,2'-联吡啶）已通过瞬态吸收测量和光谱电化学方法进行了分析。发射³ MLCTs与（GS）HOMO（H ⁺） - （GS）LUMO（E ^-）配置的最低三重态激发态而不管387或505纳米的光激发是否被使用。几微微秒后，387 nm的光激发产生了发射的^3个MLCT。相比之下，505 nm光激发填充了我们指定为³的中间激发态MLCT状态，其中孔位于转换为发射^3个MLCT之前位于不同对称性的金属中心轨道中。中间^3个和发射^3个MLCT之间在电子配置方面的差异有两个重要结果。一方面，两种状态在瞬态吸收测量中均具有非常不同的指纹吸收。另一方面，动力学障碍阻碍了重构。这样，在300 ps时标上以光谱和动力学方式跟踪转换。

更新日期：2017-09-20

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