Thiazolothiazole-Based Luminescent Metal–OrganicFrameworks with Ligand-to-Ligand Energy Transfer and Hg 2+ -Sensing Capabilities

Photoinduced electron and energy transfer through preorganized chromophore, donor, and acceptor arrays are key to light-harvesting capabilities of photosynthetic plants and bacteria. Mimicking the design principles of natural photosystems, we constructed a new luminescent pillared paddle wheel metal–organic framework (MOF), Zn2(NDC)2(DPTTZ), featuring naphthalene dicarboxylate (NDC) struts that served as antenna chromophores and energy donors and N,N′-di(4-pyridyl)thiazolo-[5,4-d]thiazole (DPTTZ) pillars as complementary energy acceptors and light emitters. Highly ordered arrangement and good overlap between the emission and absorption spectra of these two complementary energy donor and acceptor units enabled ligand-to-ligand Forster resonance energy transfer, allowing the MOF to display exclusively DPTTZ-centric blue emission (410 nm) regardless of the excitation of either chromophore at different wavelengths. In the presence of Hg2+, a toxic heavy metal ion, the photoluminescence (PL) of Zn2(NDC)2(DPTTZ...