A versatile dithienylethene-functionalized Ph-diazabutadiene (DAB) ligand: from photoswitchable main-group molecules to photochromic polymers.

Within the past decade photochromic materials, specifically dithienylethenes (DTEs), have received increased interest because of their ability to function as potential photoswitchable molecular devices and optical memory storage systems. Current research in this area has focused on incorporating organic architectures to functionalize the DTE framework and alter the resulting photophysical properties; however, their syntheses are often not trivial. In this context, we have designed a simple and versatile diimine (2) containing adjacent 2,5-dimethyl(thienyl) rings in the backbone. This redox active diimine (2) acts as a precursor to a novel photochromic ligand and has been used to coordinate to both boron and phosphorus elements, along with the synthesis of a phosphorane-side-chain functionalized polymer without further functionalization to the parent DTE framework. A study of the resulting photochromic properties of these compounds revealed that 1) the UV-visible absorption spectra of the closed-ring isomer were dependent of the element present in the N,N'-chelating pocket and 2) incorporating the dithienylethene into a side-functionalized phosphorane polymer greatly increased the closed-/open-ring reversibility and decreased the formation of by-products.