Two cyclometalated Pt(ii) complexes showing reversible phosphorescence switching due to grinding-induced destruction and crystallization-induced formation of supramolecular dimer structure.

Complexes [Pt(dfppy)(pbdtmi)]PF6 (1) and [Pt(ppy)(pbdtmi)]PF6 (2) have been constructed based on dithienylethene-based N^N ligand pbdtmi, showing supramolecular dimer structure in which two coordination cations connect each other through π⋯π stacking interaction. The crystalline state samples of both 1 and 2 reveal strong phosphorescence (emission peak: around 579 nm for 1, and 551 nm for 2). Interestingly, a grinding treatment for either 1 or 2 leads to phosphorescence switching from on-state to off-state. The subsequent crystallization with toluene recovers the initial on-state. This work discusses the relationship between the supramolecular dimer structures and the related phosphorescence switching behaviors in 1 and 2, and also explores the photochromism of pbdtmi, 1 and 2.