Luminescent palladium(0) complexes bearing N-heterocyclic carbene and phosphine ligands

Palladium(0) NHC complexes: a new avenue to highly efficient phosphorescence

“…22e , 23b In order to rigorously avoid oxygen exposure, all samples were prepared in the glovebox, with dry degassed toluene used as the solvent of choice to mitigate any solvent coordination of the vacant palladium sites, which has been shown to be possible for linear [Pd(NHC)(PR 3 )] complexes dissolved in solvents such as dichloromethane. 28 …”

“…22e,23b In order to rigorously avoid oxygen exposure, all samples were prepared in the glovebox, with dry degassed toluene used as the solvent of choice to mitigate any solvent coordination of the vacant palladium sites, which has been shown to be possible for linear [Pd(NHC)(PR 3 )] complexes dissolved in solvents such as dichloromethane. 28 The assignment of the individual absorption bands of each spectrum is made more difficult by the complex nature of the electronic structure of d 10 complexes, for which any observed MC states are symmetry-allowed. The high-energy bands are usually assigned as typical 1 p-p* transitions, but the nature of the lower energy bands is less obvious, especially when compared with literature complexes.…”

“…3 ) showed unprecedented intense emission in toluene solution; exceptionally, preliminary absorption and emission data for weakly luminescent [Pd(IPr)(PAr 3 )], 1 , has been reported although not quantified (Ar = Ph, o -Tol). 28 Herein, we report a detailed solution state photophysical study of the first examples of strongly emissive Pd(0) complexes, 2–6 ( Fig. 3 ), and compare these to the reference complex 1 .…”

“…27 Replacement of one of the phosphine ligands with a bulky IPr N-heterocyclic carbene (NHC) in [Pd(IPr)(PAr 3 )] also resulted in very weakly emissive complexes (IPr ¼ N,N 0 -bis(2,6-(diisopropyl) phenyl)imidazol-2-ylidene). 28 A dimeric palladium complex bridged by two quinone-type ligands and capped by an NHC was found to be non-emissive at room temperature and photochemically unstable. 29 Consequently, no Pd(0) complexes as of yet have been reported to be operational in a lighting device.…”

N-heterocyclic carbene metal complexes: photoluminescence and applications

“…The lifetime studied for complex 46b showed a value of 160 ns, suggesting that the emissive excited state had a triplet (Pdphosphine) 3 MLCT character. 61 Pd(II) and Pt(II) complexes with cis or trans bis(acetylide) and bis(carbene) ligands were synthesised by Venkatesan and coworkers and their photoluminescence properties studied (Fig. 20).…”