Poster Title: Organic-based Room Temperature Photochromism and Photomagnetism in 1,4-Bis(imidazolyl)benzene Systems: Sustainable Optoelectronic Devices and Optical Switches

Abstract: Photochromism and photomagnetism are key phenomena for the development of next-generation optoelectronic devices and optical switches. However, very few systems, primarily metal-based, are known to simultaneously exhibit both properties at room temperature. Here, we report 1,4-bis(4,5-diphenyl-1H-imidazol-2-yl)benzene (BDPI) as the first easily synthesized and highly stable organic photomagnet, functioning without conventional photochromic couplers or radical precursors. Solvent-assisted hydrogen bonding fosters π···πstacking between the 1,4-Bis(imidazolyl)benzene cores, enabling stable photoinduced free radicals and strong spin–spin interactions in the solid state. Halogen-substituted derivatives (Cl-BDPI & Br-BDPI) further modulate these properties, with Cl-BDPI and Br-BDPI showing rapid photochromism and stable radical generation at very high temperature (up to 170°C). Notably, Cl-BDPI undergoes a photoinduced antiferromagnetic-to-ferromagnetic transition with up to a 38% increase in magnetic moment at room temperature, which is the first occurrence of such a significant level of magnetization amplitude compared with previously reported metal−organic photomagnets.

Keywords: opto-electronics, stable organic radicals, photochromism, photomagnetism, π-stacking, photoinduced radical generation, spin−spin interactions