Fulgides are a class of organic compounds that exhibit photochromic behavior in both the solid state and in solution. These compounds have attracted considerable research interest due to their wide range of potential applications, including photochromic eyewear, smart windows, optical switches, data storage, and chemical and biological sensors. Here, we report the synthesis and crystal structures of fulgides bearing four different para-substituents on the phenyl moiety. All four molecules crystallize in space groups containing an inversion center. The distances between the two carbon atoms that would form the single C–C bond in the cyclized products fall within the range of 3.301–3.475 Å. The observed structural variations are attributed to intermolecular interactions based on Hirshfeld surface analysis. The fulgides exhibit photochromism, but they are not expected to display ferroelectric behavior due to their crystallization in centrosymmetric space groups.

Graphitic carbon nitride is a semiconducting material of a graphite-like 2D layered structure. It is well known for its photocatalytic properties, which can be exploited for solar-light-driven water splitting and degradation of organic pollutants. Here, we report its capabilities of catalyzing the reduction of the azo bond by hydrazine to two amines under visible light. This photocatalytic reaction provides a novel, appealing way to reduce azo dye wastes as pollutants other than degradation. With this method, the azo dye wastes can be photochemically converted to amines, which can be used as precursors for new azo dyes.

Fulgides are a class of organic compounds that have been extensively investigated because of their photochromic properties and the wide range of applications arising from them. Fulgimides, an important subclass of fulgides, contain a succinimide moiety in place of the succinic anhydride functionality found in fulgides. Isofulgimides are constitutional isomers of fulgimides in which the succinimide ring is replaced by a 5-iminodihydrofuran-2(3H)-one moiety. Although isofulgimides also exhibit photochromism, their synthesis and photochromic behavior have received considerably less attention than those of other fulgide derivatives. Reports on isofulgimides remain scarce, and crystallographic investigations are particularly limited. As part of our ongoing efforts to develop novel photochromic compounds, we synthesized a unique dimeric isofulgimide featuring an N–N single-bond linkage. Herein, we report its synthesis, crystal structure, and photochromic properties.

Fulgides are a group of organic compounds that exhibit photochromic properties both in solid state and in solutions. The compounds attracted research attention due to their wide potential applications including photochromic eyewear, smart windows, optical switch, data storage, chemical and biological sensors. We are reporting here the synthesis and crystal structures of fulgides of four different substituents at the para position of a phenyl moiety in the molecules. It was found among the 4 structures that 1) all the 4 compounds packed in space groups of an inversion center; 2) the distance between the two carbon atoms C8 and C11, which form a single C-C bond in the cyclized products, falls in the range of 3.5-3.7 Å; 3) the torsion angle, defined by C6-C3-C4-C11, falls in the range of 23.4o to 32.5o. The fulgides exhibited photochromism. The fulgides should have no ferroelectric property due to their crystallization into centrosymmetric spaces groups.

Isofulgimides, characterized by a 5-iminodihydrofuran-2(3H)-one moiety, constitute a subgroup of fulgide derivatives that have received comparatively limited attention despite their potential photochromic applications. Herein, we report the synthesis, crystal structure, and preliminary photochromic characterization of a structurally unique dimeric isofulgimide in which two conjugated systems are connected through a single N–N bond to form a more extensively conjugated system. The compound crystallizes in the centrosymmetric triclinic space group P-1, with disorder of the phenyl groups in close intermolecular contact and strong interactions, including strong π-π stacking. the molecular structure of each half of the dimer closely superimposes on that of the starting fulgide. In solution, irradiation with a low-power 405 nm laser produced a new broad absorption band centered at approximately 510 nm, indicating photoinduced isomerization. After irradiation was discontinued, this band gradually disappeared within approximately 42 min, demonstrating thermal recovery of the initial form. Because isofulgimides remain relatively uncommon and crystallographic studies of dimeric isofulgimides have not previously been reported, these findings provide new structural and preliminary photochemical insights into this understudied class of photochromic compounds.