Platinum(II)-Substituted Phenylacetylide Complexes Supported by Acyclic Diaminocarbene Ligands.

We introduce phosphorescent platinum aryl acetylide complexes supported by tert -butyl-isocyanide and strongly σ-donating acyclic diaminocarbene (ADC) ligands. The precursor complexes cis -[Pt(CN t Bu) 2 (C≡CAr) 2 ] ( 4a-4f ) are treated with diethylamine, which undergoes nucleophilic addition with one of the isocyanides to form the cis -[Pt(CN t Bu)(ADC)(C≡CAr) 2 ] complexes ( 5a-5f ). The new compounds incorporate either electron-donating groups (4-OMe and 4-NMe 2 ) or electron-withdrawing groups [3,5-(OMe) 2 , 3,5-(CF 3 ) 2 , 4-CN, and 4-NO 2 ] on the aryl acetylide. Experimental HOMO-LUMO gaps, estimated from cyclic voltammetry, span the range of 2.68-3.61 eV and are in most cases smaller than the unsubstituted parent complex, as corroborated by DFT. In the ADC complexes, peak photoluminescence wavelengths span the range of 428 nm ( 2a , unsubstituted phenylacetylide) to 525 nm ( 5f , 4-NO 2 -substituted), with the substituents inducing a red shift in all cases. The phosphorescence E 0,0 values and electrochemical HOMO-LUMO gaps are loosely correlated, showing that both can be reduced by either electron-donating or electron-withdrawing substituents on the aryl acetylides. The photoluminescence quantum yields in the ADC complexes are between 0.044 and 0.31 and the lifetimes are between 4.8 and 14 μs, a factor of 1.8-10× higher (for Φ PL ) and 1.2-3.6× longer (for τ) than the respective isocyanide precursor (Φ PL = 0.014-0.12, τ = 2.8-8.2 μs).