Wegner and Heindl showed that the λ max and t 1/2 of hemi-2thiophenes with a phenyl terminus can be tuned through functionalization on both aryl rings. They synthesized a series of azothiophenes with substituents on the meta and para positions on the phenyl ring and at the 5-position on the thiophene ring. They determined the E-isomer λ max and Zisomer t 1/2 for each. They reported λ max values approaching 405 nm (through substitution of the thiophene ring with a methoxy group) and high (>99%) E → Z photoconversion efficiencies (through substitution of the phenyl ring at the meta position with a CN functional group). Although the 2-hemi-thiophenes displayed red-shifted E-isomer λ max values ranging from 45-85 nm compared to azobenzene, the t 1/2 lifetimes were shorter (maximum t 1/2 of 17.7 hours) than those of azobenzene (2 days in CH 3 CN).