Stepwise Strategy to Cyclometallated PtII Complexes with N-Heterocyclic Carbene Ligands: A Luminescence Study on New [beta]-Diketonate Complexes

• Published in: Chemistry : a European journal Vol. 21; no. 4; p. 1620
• Main Authors: Fuertes, Sara, Garcia, Hector, Peralvarez, Mariano, Hertog, Wim, Carreras, Josep, Sicilia, Violeta
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 19.01.2015
• Subjects: Chemistry; Ligands
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201404915

The imidazolium salt 3-methyl-1-(naphthalen-2-yl)-1H-imidazolium iodide (2) has been treated with silver(I) oxide and [{Pt(µ-Cl)(η3-2-Me-C3H4)}2] (η3-2-Me-C3H4=η3-2-methylallyl) to give the intermediate N-heterocyclic carbene complex [PtCl(η3-2-Me-C3H4)(H$\widehat{CC}$*-[kappa]C*)] (3) (H$\widehat{CC}$*-[kappa]C*=3-methyl-1-(naphthalen-2-yl)-1H-imidazol-2-ylidene). Compound 3 undergoes regiospecific cyclometallation at the naphthyl ring of the NHC ligand to give the five-membered platinacycle compound [{Pt(µ-Cl)($\widehat{CC}$*)}2] (4). Chlorine abstraction from 4 with [beta]-diketonate Tl derivatives rendered the corresponding neutral compounds [Pt($\widehat{CC}$*)(L-O,O')] {L=acac (HL=acetylacetone) 5, phacac (HL=1,3-diphenyl-1,3-propanedione) 6, hfacac (HL=hexafluoroacetylacetone) 7}. All of the compounds (3-7) were fully characterized by standard spectroscopic and analytical methods. X-ray diffraction studies were performed on 5-7, revealing short PtPt and π-π interactions in the solid-state structure. The influence of the R-substituents of the [beta]-diketonate ligand on the photophysical properties and the use of the most efficient emitter, 5, as phosphor converter has also been studied.