Thiophene-substituted phenoxyl-imidazolyl radical complexes with high photosensitivity

Phenoxyl-imidazolyl radical complex (PIC) is a novel photochromic compound, which generates two nonequivalent radicals upon UV light irradiation. While the color fading speed of PIC can be tuned from tens of nanoseconds to seconds, the low visible sensitivity has limited their potential applications. Herein, we developed novel thiophene-substituted PIC derivatives. The visible sensitivity and the increased absorption coefficient were achieved with keeping the moderate color fading speed by introducing a phenyl group at the 5-position of the thiophene ring.