Anion-π Interaction-Induced Room-Temperature Phosphorescence of a Polyoxometalate-Based Charge-Transfer Hybrid Material.

Room-temperature phosphorescence (RTP) was realized for the first time in a polyoxometalate-based charge-transfer (CT) hybrid material bearing polyoxometalates (POMs) as electron-donors (D) and rigid naphthalene diimides (NDIs) as electron-acceptors (A), meanwhile, this hybrid material displayed photochromism as well. The significant D-A anion-π interaction induced an additional through-space charge-transfer pathway. The resulting suitable D-A CT states can efficiently bridge the relatively large energy gap between the NDI-localized 1 π-π* and 3 π-π* states and thus trigger the ligand-localized phosphorescence (3 π-π*).