Switching on room-temperature phosphorescence of photochromic hybrid heterostructures by anion-π interactions

Room-temperature phosphorescence (RTP) has attracted much attention in the past decades due to its potential applications in optoelectronic devices and bioimaging. So far, most available RTP materials are pure inorganic or organic compounds, few are involved in the organic-inorganic hybrid complexes. The donor-acceptor (D-A) hybrid heterostructures are an emerging class of organic-inorganic hybrid complexes composed of semi-conductive organic and inorganic tectons at the molecular level. For these unique hybrids, the primary properties are photochromism and photoinduced electron transfers. Herein, we have demonstrated that the combination of naphthalene diimide (NDI) tectons bearing two divergently oriented pyridyl protons with three polyoxometalate (POM) anions (SiW12O404-, PW12O403- or PMo12O403- resulted in three isostructural D-A hybrid heterostructures with an alternate arrangement of segregated POM anions and 1-D H-bonded NDI networks as electron donors and acceptors, respectively. Due to the compact contacts between POM anions and NDI tectons induced by charge assisted anion-pi interactions, not only the photochromic speeds of three D-A hybrid heterostructures have been enhanced, but more interestingly their RTP emissions of have also been switched on, and their photoluminescence quantum yields are dependent on anion-pi interaction strengths.