The reasons for ligand-dependent quantum yields and spectroscopic properties of platinum(ii) complexes based on tetradentate O^N^C^N ligands: a DFT and TD-DFT studyElectronic supplementary information (ESI) available. See DOI: 10.1039/c3dt52616j

DFT and TD-DFT methods have been employed to theoretically investigate the properties of three recently synthesized green-emitting platinum( ii ) complexes ( 1-3 ) bearing tetradentate O^N^C^N ligands (O^C^N^C = 2-(4-(3,5-di- tert -butylphenyl)-6-(3-(pyridin-2-yl)phenyl)-pyridin-2-yl)phenolate and its derivatives) that have been testified to be good emitters in organic light-emitting diodes (OLEDs), especially for complex 3 . The effect of the variation of the substituents on the electronic and optical properties is emphatically explored. Our calculation results reveal that the introduction of an electron-releasing group on one phenyl ring of the O^C^N^C ligand (complex 2 ) does not result in a distinct alteration of the spectra. However, the incorporation of the norbornane group to the O^C^N^C ligand (complex 3 ) leads to a blue-shift in the absorption and emission spectra as compared with 1 . In addition, how the absorption and emission spectra are affected by the solvent polarity is studied. Both the absorption and the emission spectra display red-shifts of various degrees with the decrease of the solvent polarity. The different phosphorescent quantum yields of the three complexes are compared. It is reasonable to believe that the high 3 MLCT (metal-to-ligand charge transfer) contribution and high percentage of the metallic character ( M c , %) in the emission process, as well as the largest vertical transition energy for 3 , result in the highest quantum efficiency. DFT and TD-DFT methods have been employed to theoretically investigate the properties of three recently synthesized green-emitting platinum( ii ) complexes ( 1-3 ) that have been testified to be good emitters in organic light-emitting diodes (OLEDs).