Benzo[b]Germole-Fused Diarylethenes as Photochromic Organogermanium Compounds

The molecular design of various heterocycles incorporated into photochromic diarylethenes plays an important role in diversifying functionality. Herein, we report the design, synthesis, and structural characterization of photochromic benzo[b]germole-fused diarylethenes. Photochromic behaviors including clean conversion between the open and the photogenerated closed forms under ambient conditions over multiple photoswitching cycles with insignificant loss of photochemical reactivity, thermal irreversibility with negligible backward reaction of the photogenerated closed form back to the open form even at 100 °C, and satisfactory and comparable photochromic quantum yields for the forward and backward photoswitching processes are observed. This work demonstrates the employment of a rarely explored germole ring with weak aromaticity as a versatile building block for the ethene bridge of the photochromic diarylethene, which is the first of its kind to construct photochromic materials for potential applications, further expanding the diversity of the heterocycle-fused diarylethene-based system with interesting photocontrolled functions.