Photochromic Dy-Phosphonate Assembled by a Pyridine Derivative: Synthesis, Structure, and Light-Enhanced Room-Temperature Phosphorescence

Hydroxyethylidene diphosphonate (HEDP) and tris(4-pyridyl)amine (TPA) are employed to assist the preparation of a Dy(III)-phosphonate in this work, namely, {[Dy2(H2-HEDP)4]3•2(H3-TPA)•2(H4-HEDP)•xsolvent} (1). The compound features the anionic one-dimensional chain structure templated by the cationic H3-TPA and uncoordinated H4-HEDP molecules. Through the hydrogen bonds between the guest cations and host Dy(III)-phosphonate skeletons, a supramolecular architecture is finally constructed, displaying photochromism and room-temperature phosphorescence (RTP) behaviors. Interestingly, through the protonation of TPA molecules, the radicals generated after photochromism still remain a highly stable character, accomplishing an extremely long-lived state of charge separation. Moreover, the photogenerated radicals can greatly prompt the RTP performance of compound 1, which offers a promising strategy for the construction of tunable optical materials.