Bis(diphenylphosphinyl)-functionalized dipyrido-annulated NHC towards copper() and silver()

The coordination chemistry of our recently isolated bis(diphenylphosphinyl)-functionalized dipyrido-annulated NHC (N-heterocyclic carbene), dpa P2 -NHC , towards copper( i ) and silver( i ) has been studied. Based on dpa P2 -NHC , two dinuclear silver and copper complexes [ 2 , ( Ag 2 L 2 ) and 3 , ( Cu 2 L 2 )], two tetranuclear copper complexes { 4 , [Cu 4 L 2 (NCMe) 2 ] and 6 , (Cu 4 LBr 4 )} and a pentanuclear copper complex [ 5 , (Cu 5 L 2 Br 3 )] exhibiting strong intramolecular metal-metal interactions were achieved and characterized. All the complexes exhibited dynamic behavior in solution, in which the NMR coalescence of 2 was well resolved at low temperature (below 208 K) and dissociation for 2 was observed according to the calculated Eyring plot. Ag 2 L 2 ( 2 ) shows a similar coordination sphere to that of our previously reported gold complex Au 2 L 2 ; Cu 2 L 2 ( 3 ) features a rare μ 2 -bridging carbene and a terminal carbene; Cu 4 LBr 4 ( 6 ) is neutral and monomeric, in which four copper atoms were rigidly fixed by the tridentate dpa P2 -NHC ligand and bromide anions. All the complexes ( 2-6 ) were luminescent at room temperature, in which 4-6 provided phosphorescence at 77 K. Based on the comparison of the emission bands with dpa P2 -NHC , we conclude that the electronic transitions of 2-6 can be attributed to the ligand-centered (LC) transitions. Sterically rigid bis(phosphinyl)dipyrido-annulated NHC coordinates with Ag( i ) and Cu( i ) centres to form luminescent multinuclear complexes.