Green-emitting iridium(III) complexes containing sulfanyl- or sulfone-functionalized cyclometallating 2-phenylpyridine ligands

A series of [Ir(C boolean AND N)(2)(bpy)][PF6] complexes in which the cyclometallating ligands contain fluoro, sulfane or sulfone groups is reported. The conjugate acids of the C boolean AND N ligands in the complexes are 2-(4-fluorophenyl) pyridine (H1), 2-(4-methylsulfonylphenyl) pyridine (H3), 2-(4-tbutylsulfanylphenyl) pyridine (H4), 2-(4-(t)butylsulfonylphenyl) pyridine (H5), 2-(4-(n)dodecylsulfanylphenyl) pyridine (H6), 2-(4-(n)dodecylsulfonylphenyl) pyridine (H7). The single crystal structures of H3 and H5 are described. [Ir(C boolean AND N)(2)(bpy)][PF6] with C boolean AND N = 1, 3, 4, 5 and 7 were prepared from the appropriate [Ir2(C boolean AND N)(4)Cl-2] dimer and bpy; the structure of [Ir-2(3)(4)Cl-2]center dot 2CH(2)Cl(2) was determined. [Ir(6) 2(bpy)][PF6] was prepared by nucleophilic substitution starting from [Ir(1) 2(bpy)][PF6]. The [Ir(C boolean AND N)(2)(bpy)][PF6] complexes have been characterized by NMR, IR, absorption and emission spectroscopic and mass spectrometric methods. The single crystal structures of enantiomerically pure.-[Ir(1) 2(bpy)][PF6] and of rac-4{[Ir(1)(2)(bpy)][PF6]}center dot Et2O center dot 2CH(2)Cl(2) are described, and the differences in inter-cation packing in the structures compared. [Ir(1) 2(bpy)][PF6], [Ir(4)(2)(bpy)][PF6] and [Ir(6)(2)(bpy)][PF6] (fluoro and sulfane substituents) are yellow emitters (.max em between 557 and 577 nm), and the room temperature solution emission spectra are broad. The sulfone derivatives [Ir(3)(2)(bpy)][PF6], [Ir(5)(2)(bpy)][PF6] and [Ir(7)(2)(bpy)][PF6] are green emitters and the emission spectra are structured (.max em = 493 and 523 to 525 nm). High photoluminescence quantum yields (PLQYs) of 64-74% are observed for the sulfone complexes in degassed solutions. The emission lifetimes for the three complexes containing sulfone substituents are an order of magnitude longer (2.33 to 3.36 mu s) than the remaining complexes (0.224 to 0.528 mu s). Emission spectra of powdered solid samples have also been recorded; the broad emission bands have values of lambda(max)(em) em in the range 532 to 558 nm, and PLQYs for the powdered compounds are substantially lower (<= 23%) than in solution. Trends in the redox potentials for the [Ir(C boolean AND N)(2)(bpy)][PF6] complexes are in accord with the observed emission behaviour.