Abstract
We synthesized 4TIPS-pen, a pentacene derivative bearing TIPS-ethynyl groups at the 5,7,12,14-positions via a modified route. The compound showed polymorphism, forming green crystals with a twisted backbone and blue crystals with a planar backbone. UV-vis spectra and theoretical calculations revealed distinct optical behaviors linked to structural differences. 4TIPS-pen is photounstable, and we confirmed the product structure using X-ray analysis. These results highlight structure-property relationships and offer design guidelines for extended π-conjugated pentacenes.