Heteroleptic Ir() and Pt() 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)]·3CH 3 OH ( 1 ) and [Pt(dfppy)(BrL)]·CH 3 OH ( 2 ) have been prepared based on the same ligands including bisthienylethene BrLH and dfppyH = (2-(2,4-difluorophenyl)-pyridine). Complexes 1 and 2 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 1 , and a layer structure in 2 . Upon irradiation with 380 nm light, compound 2 shows photochromic behavior in CH 2 Cl 2 , with a color change from nearly colorless to light green. However, no photochromism was observed in compound 1 . At room temperature, compound 1 reveals phosphorescence with a predominant 3 MLCT character both in CH 2 Cl 2 solution (emissions at 495 and 513 nm) and in the solid state (emission at 524 nm). Compound 2 exhibits phosphorescence with a predominant 3 LC character in CH 2 Cl 2 solution (emission at 508 nm), but it is almost non-luminescent in the solid state. Our experimental results demonstrate that the metal centers in 1 and 2 could significantly influence their structures, photochromism, and luminescence behaviors. Based on bisthienylethene BrLH, [Ir(dfppy) 2 (BrL)]·3CH 3 OH ( 1 ) and [Pt(dfppy)(BrL)]·CH 3 OH ( 2 ) have been prepared. The two complexes are significantly different in structure, luminescence and photochromic behavior, due to their different metal centers.