Heteroleptic Ir(iii) and Pt(ii) complexes based on 2-(2,4-difluorophenyl)-pyridine and bisthienylethene BrLH: the influence of the metal center on structures, luminescence and photochromism.

Heteroleptic complexes [Ir(dfppy)2(BrL)]·3CH3OH () and [Pt(dfppy)(BrL)]·CH3OH () have been prepared based on the same ligands including bisthienylethene BrLH and dfppyH = (2-(2,4-difluorophenyl)-pyridine). Complexes and reveal distinct crystal structures. The BrL(-) anion uses its phenol-imidazole moiety to coordinate with an {Ir(dfppy)2}(+) unit in the former, while with a {Pt(dfppy)}(+) unit in the latter. Neighboring [Ir(dfppy)2(BrL)]/[Pt(dfppy)(BrL)] molecules are connected through extensive hydrogen bonds and aromatic stacking interactions, thus forming a supramolecular chain structure in , and a layer structure in . Upon irradiation with 380 nm light, compound shows photochromic behavior in CH2Cl2, with a color change from nearly colorless to light green. However, no photochromism was observed in compound . At room temperature, compound reveals phosphorescence with a predominant (3)MLCT character both in CH2Cl2 solution (emissions at 495 and 513 nm) and in the solid state (emission at 524 nm). Compound exhibits phosphorescence with a predominant (3)LC character in CH2Cl2 solution (emission at 508 nm), but it is almost non-luminescent in the solid state. Our experimental results demonstrate that the metal centers in and could significantly influence their structures, photochromism, and luminescence behaviors.