Crystal Structures of Novel Phenyl Fulgides

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.