Professor Dinesh (Dan) Patel of Penn State Hazelton

"Toward Photoresponsive Linkers for Metal-Organic Frameworks: Diarylethenes Based on Naphthoquinone"

Photochromic compounds are able to switch between two unique molecular forms using light as a trigger. Diarylethene photochromes, which typically employ a perfluorocyclopentene bridging group bound to substituted thiophenes, show promise for use in advanced organic electronic and photonic materials with burgeoning considerations for biological applications; however, these compounds typically require UV light for photoswitching in at least one direction, thus limiting their appeal. We have recently started employing naphthoquinone as a bridging group and found that the resulting compounds can switch using visible light only. These compounds are also unique in that switching can also be affected chemically using strong Lewis acids. Typically, however, naphthoquinone containing diarylethenes are synthesized using Stille coupling methodology, which limits the functional groups that can be incorporated into target molecules. We recently began to rely on Suzuki methodology, allowing for the inclusion of functional groups not otherwise accessible with Stille synthetic routes. These functional groups, including carboxylates and nitriles – and eventually others, open the possibility to begin using these naphthoquinones in functional materials where the ability to bind to ions is key. This talk will focus on the synthetic challenges faced to achieve target molecules, the functional groups we have accessed, and the unexpected characteristics these molecules exhibit.