Anthraquinone-Imide-Based Dimers: Synthesis, Piezochromism, Liquid Crystalline, and Near-Infrared Electrochromic Properties

A series of anthraquinone-imide-based dimers, C5 -AQI-Si2, C5 -AQI-Si3, C5 -AQI-Si4, and C5 AQI-Si8, have been prepared by the hydrosilylation of N-(hex-5-enyl)-6-(40-((S)-2-methylbutoxy)phenyl)anthraquinone-2,3-dicarboxylic imide and hydride-terminated siloxanes with different lengths. Their liquid crystalline behaviors, and piezochromic and near-infrared electrochromic properties have been characterized by DSC, wide-angle X-ray diffraction, cyclic voltammetry, and UV–vis–NIR spectroscopy. Although anthraquinone imide is not liquid crystalline by itself, all the dimers formed a smectic A mesophase. Under moderate pressure, the color of the dimers changed from light yellow to deep red. Upon reduction to a radical anionic state, the dimers exhibited an intense NIR absorption at 844 nm. These anthraquinone-imide-based dimers are probably the first multifunctional molecules with combined liquid crystalline, mechanochromic, and NIR electrochromic properties.