Controlling Energy Gaps of π‐Conjugated Polymers by Multi‐Fluorinated Boron‐Fused Azobenzene Acceptors for Highly Efficient Near‐Infrared Emission
Controlling Energy Gaps of π‐Conjugated Polymers by Multi‐Fluorinated Boron‐Fused Azobenzene Acceptors for Highly Efficient Near‐Infrared Emission
复制标题
通过多氟化硼稠合偶氮苯受体控制π共轭聚合物的能隙以实现高效近红外发射
DOI：
10.1002/asia.202100037
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
Chujo Yoshiki
中科院分区：
文献类型：
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作者：
Gon Masayuki;Wakabayashi Junko;Nakamura Masashi;Tanaka Kazuo;Chujo Yoshiki
我们证明了多氟硼稠合偶氮苯（BAz）配合物可以在电子给体-受体（D-A）型π共轭聚合物中作为强电子受体。发现了位置依赖性取代效应，并且最低未占分子轨道（LUMO）的能级被取代基显著降低。结果，所获得的聚合物显示出近红外（NIR）发射（λPL=758-847 nm），具有高的绝对光致发光量子产率（ΦPL=7-23%），其源自BAz部分的低LUMO能级（−3.94至−4.25 eV）。 由于BAz单元固有的固态发射特性，在膜状态下检测到更深的NIR发射（λPL=852980 nm）。 清晰的溶剂效应证明了NIR发射来自源于强D-A相互作用的电荷转移态。通过密度泛函理论的计算，可以很好地理解和预测电子对前线轨道的影响。这项研究证明了对BAz单元进行修饰的有效性，通过微调能隙产生强的电子接受单元，这可能是设计NIR吸收和发射材料的有前途的策略。
We demonstrate that multi‐fluorinated boron‐fused azobenzene (BAz) complexes can work as a strong electron acceptor in electron donor‐acceptor (D‐A) type π‐conjugated polymers. Position‐dependent substitution effects were revealed, and the energy level of the lowest unoccupied molecular orbital (LUMO) was critically decreased by fluorination. As a result, the obtained polymers showed near‐infrared (NIR) emission (λPL=758–847 nm) with high absolute photoluminescence quantum yield (ΦPL=7–23%) originating from low‐lying LUMO energy levels of the BAz moieties (−3.94 to −4.25 eV). Owing to inherent solid‐state emissive properties of the BAz units, deeper NIR emission (λPL=852980 nm) was detected in film state. Clear solvent effects prove that the NIR emission is from a charge transfer state originating from a strong D‐A interaction. The effects of fluorination on the frontier orbitals are well understandable and predictable by theoretical calculation with density functional theory. This study demonstrates the effectiveness of fluorination to the BAz units for producing a strong electron‐accepting unit through fine‐tuning of energy gaps, which can be the promising strategy for designing NIR absorptive and emissive materials.