Using Meta Conjugation To Enhance Charge Separation versus Charge Recombination in Phenylacetylene Donor−Bridge−Acceptor Complexes

A pair of donor−bridge−acceptor electron-transfer complexes, with a carbazole donor and a naphthalimide acceptor connected by either a para- or meta-conjugated phenylacetylene bridge, are synthesized and studied using time-resolved and steady-state spectroscopy. These experiments show that the charge separation times, which depend on the coupling of the donor and acceptor through the excited bridge moiety, are similar for the two molecules (Meta and Para). The charge recombination time, however, is a factor of 10 slower for Meta than for Para. These results are related to changes in the electronic coupling of the bridge depending on its electronic state, and show that meta-conjugated bridges provide a possible motif for the design of asymmetric molecular wires.

一对由咔唑供体和萘酰亚胺受体组成的供体-桥-受体电子转移复合物，通过对位或间位共轭的苯乙炔桥连接，已通过时间分辨和稳态光谱学方法进行合成与研究。实验结果表明，电荷分离时间，该时间依赖于供体和受体通过激发的桥联部分之间的耦合，对于两种分子（间位和邻位）而言相似。然而，电荷重组时间，对于间位而言，比邻位慢了十倍。这些结果与桥的电子耦合随其电子状态的变化有关，并表明间位共轭桥为设计非对称分子导线提供了一种可能的模式。