Generation Dependent Ultrafast Charge Separation and Recombination in a Pyrene-Viologen Family of Dendrons
Generation Dependent Ultrafast Charge Separation and Recombination in a Pyrene-Viologen Family of Dendrons
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DOI：
10.1021/acs.jpcb.6b01844
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发表时间：
2016-05-12
影响因子：
3.3
通讯作者：
Piotrowiak, Piotr
中科院分区：
文献类型：
--
作者：
Gong, Zheng;Bao, Jianhua;Piotrowiak, Piotr
在甲基紫精（MV 2+）树枝状分子跨越四代，G0到G3的同源家族中，研究了树枝状网络拦截电子和延长短寿命光致电荷分离（CS）状态的寿命的能力。CS状态在母体芘亚甲基紫精G0系统与一个单一的受体表现出极短的寿命τ = 0.72 ps。紫精网络的扩展通过允许注入的电子进一步远离供体迁移而将较慢的组分引入到复合动力学中。种群的长寿命部分以G3 > G2 > G1 > G0的顺序单调增加，而相应的重组率降低。在最高代的树突类似于14%的CS状态人口经历了10倍或更大的寿命延长。跨越多个紫精单元的长距离隧穿和顺序的站点到站点跳跃都有助于整体效果。在电荷分离时沉积在顶端紫精中的大量过量能量和低位π轨道的延伸网络的存在可能促进电子进一步沿着树枝状分子穿梭。
The ability of a dendritic network to intercept electrons and extend the lifetime of a short-lived photoinduced charge separated (CS) state was investigated in a homologous family of methyl viologen (MV2+) dendrons spanning four generations, G0 through G3. The CS state in the parent pyrene methylene viologen G0 system with a single acceptor exhibits an extremely short lifetime of tau = 0.72 ps. The expansion of the viologen network introduces slower components to the recombination kinetics by allowing the injected electron to migrate further away from the donor. The long-lived fraction of the population increases monotonically in the order G3 > G2 > G1 > G0, while the respective recombination rates decrease. In the highest generation of the dendron similar to 14% of the CS state population experiences a 10-fold or greater lifetime extension. Long range tunneling across multiple viologen units and sequential site-to-site hopping both contribute to the overall effect. The large excess energy deposited in the apical viologen upon charge separation and the presence of an extended network of low lying pi-orbitals likely facilitate shuttling the electron further down the dendron.