Carbazole-functionalized polyphenylene-decorated solid state emissive D-A-D molecules: reduced donor-acceptor interaction and enhanced emission in the solid state.
Carbazole-functionalized polyphenylene-decorated solid state emissive D-A-D molecules: reduced donor-acceptor interaction and enhanced emission in the solid state.
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DOI：
10.1039/c5cp02234g
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发表时间：
2015-08
期刊：
影响因子：
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通讯作者：
Gopal Singh;V. Bhalla;Manoj Kumar
中科院分区：
文献类型：
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作者：
Gopal Singh;V. Bhalla;Manoj Kumar
以咔唑为供体，2，5-二芳基-1，3，4-恶二唑、二苯并噻吩基-S、S-二氧化物和苯并[1，2，5]噻二唑为受体，合成了一系列新的D-A-D分子(1-3)。聚亚苯基树枝也被加入，以防止聚集体中面对面的π-π堆积。与传统的D-A体系不同，这些衍生物(1-3)在固态时会出现ACQ问题和大的红移，而不会发生红移或荧光猝灭，表现出良好的固态发光行为。目前的结果表明，仅仅将供体-受体系统与较大的树枝相结合并不足以产生有效的固态发射，但更重要的是防止聚集体中供体和受体之间的界面相互作用。在衍生物3的情况下，分子完全平坦化的限制和受体附近的空间位阻可以有效地阻止分子间的给体-受体相互作用，从而导致聚集体中发射的增强。而在衍生物1的情况下，由于聚集体中紧密的分子堆积形成弱发光物种，空间上不受阻碍的受体很容易被给体接近。
A new series of D-A-D molecules (1-3) with carbazole as a donor and 2,5-diaryl-1,3,4-oxadiazole, dibenzothiophene-S,S-dioxide and benzo[1,2,5]thiadiazole as acceptors have been synthesized. Polyphenylene dendrons have also been incorporated to prevent the face to face π-π stacking in aggregates. Unlike traditional D-A systems, which show ACQ problems and large red shifts in the solid state, these derivatives (1-3) exhibit good solid state luminescence behavior without undergoing a red shift or fluorescence quenching. The present results indicate that just the combination of a donor-acceptor system with bulkier dendrons is not enough to generate efficient solid state emissions but the prevention of co-facial interaction between donors and acceptors in aggregates is more important. In the case of derivative 3, restriction of complete molecular planarization and steric hindrance near the acceptor can effectively prevent intermolecular donor-acceptor interactions, thus leading to enhanced emission in aggregates. While in the case of derivative 1, a sterically unhindered acceptor is easily approached by a donor due to close molecular packing in aggregates forming weakly luminescent species.