We demonstrate near-infrared (NIR) absorptive and emissive poly(p-phenylene vinylene) (PPV)-type π-conjugated polymers based on hypervalent tin-fused azobenzene (TAz) complexes. Taking advantage of the inherent narrow-energy gap of TAz complexes originating from the three-center four-electron (3c-4e) bond and nitrogen–tin (N–Sn) coordination, the synthesized polymers, TAz-PPVs, showed absorption, and emission in wavelength regions of >750 and 810 nm in diluted solution, respectively. From the experimental and theoretical investigations, the elevation of the highest occupied molecular orbital (HOMO) and the reduction of the lowest unoccupied molecular orbital (LUMO) were simultaneously shown to be caused by the extension of π-conjugation. The effective conjugation length was calculated to be n > 10 (n: degree of polymerization), and the value was comparable to conventional PPV systems. Through this research, we revealed that π-conjugated systems including hypervalent bonds were able to expand π-conjugation. According to the concept of “element blocks”, the development of heteroatom-containing narrow-energy-gap monomers should be a novel approach for the construction of new NIR-absorptive and emissive bland materials.

我们展示了基于高价锡稠合偶氮苯 (TAz) 配合物的近红外 (NIR) 吸收性和发射性聚（对亚苯基亚乙烯基）（PPV）型 π 共轭聚合物。利用源自三中心四电子 (3c-4e) 键和氮-锡 (N-Sn) 配位的 TAz 配合物固有的窄能隙，合成的聚合物 TAz-PPVs 显示出吸收和分别在稀释溶液中>750 和 810 nm 的波长区域发射。从实验和理论研究来看，最高占据分子轨道（HOMO）的升高和最低未占据分子轨道（LUMO）的降低同时被证明是由π共轭的延伸引起的。计算出的有效共轭长度为n > 10（n：聚合度），该值与传统 PPV 系统相当。通过这项研究，我们发现包括高价键在内的 π 共轭系统能够扩展 π 共轭。根据“元素块”的概念，开发含杂原子的窄能隙单体应该是构建新的近红外吸收和发射平淡材料的新途径。