A Remarkable Isotope Effect on the Photochromism of trans-Biindenylidenedione in the Solid State

Abstract

The yellow crystals of 3,3'-diaryl-3H,3'H-[2,2']biindenylidene-1,1'-dione 1 and 1-d₂ were immediately changed to red crystals upon photoirradiation in the solid state. The red crsytals of 1-d₂ returned back to the original yellow crystals under dark for 72 h, whereas that of 1 faded within 2 h.