Azobenzene is one of the most famous chromophores, and various types of dyes are constructed with the azobenzene structures. Furthermore, azobenzene is also well known as photoisomerization-presenting scaffold and has been applied for photoresponsive molecular switches. However, there are only few reports for the application to luminescence materials. We have recently reported that the fused azobenzene-boron complex 1 exhibited aggregation-induced emission and was good for solid-state luminescence materials (Figure 1). Moreover, we have found that tin complex 2 showed luminescence in the dilute solution. Compound 2 had a five coordinate structure and a narrow HOMO-LUMO energy bandgap caused by three-center four- electron bonds. We expected that the substitution of tin to germanium should lower the HOMO- LUMO energy bandgap, and the resulting azobenzene-germanium complexes should show near- infrared emission. Herein, we synthesized azobenzene-germanium complexes and investigated their photophysical properties.
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