Effects of π-Extension on Pyrrole Hemithioindigo Photoswitches

The most red-shifted hemithioindigo photoswitches have been identified through systematic introduction of aryl units to a parent pyrrole hemithioindigo photoswitch. Increasing the size of the 5’-aryl substituent is ineffective at producing further redshifted chromophores. A second generation of 3’,5’-diarylated photoswitches which possess increased tunability is reported. Experimental and computational evidence indicates the 4’ position is electronically isolated from the bulk of the conjugated system.