The result in Figure suggests that replacing one of the phenyl groups in azobenzene with a cross-conjugated thiophene ring increases the t 1/2 by 54 days, while the E-isomer λ max is nearly identical (320 nm for 1-E and 330 nm for azobenzene). Scheme 1 shows all 26 azoarenes included in this study. We present 13 with no substituents on the thiophene ring and 13 with 2,5-dimethoxy thiophenes. We substituted methoxy groups on the thiophene because Wegner observed longer t 1/2 values for azothiophenes with EDGs substituted at the 4-position. Scheme 1. Parent structure for hemi-azothiophenes, and substituted hemi-azothiophene photoswitches tested for this work.