Planarization‐Induced Activation Wavelength Red‐Shift and Thermal Half‐Life Acceleration in Hydrazone Photoswitches

The optimization and modulation of the properties of photochromic compounds, such as their activation wavelengths and thermal relaxation half‐lives (τ (1/2)), are essential for their adaptation in various applications. In this work, we studied the effect of co‐planarization of the rotary fragment of two photochromic hydrazones with the core of the molecule on their switching properties. The Z and E isomers of both compounds exhibit red‐shifted absorption bands relative to their twisted versions, allowing for their photoswitching using longer wavelengths of light. Additionally, the thermal half‐lives of both hydrazones are drastically shortened from hundreds of years to days.