†Electronic Supplementary Information (ESI) available: X-ray crystallographic data in CIF format for the complexes Ir2 and Ir4 [CCDC 973778 (Ir2) and 1005716 (Ir4)], NMR and MASS spectra of ligands and complexes, TGA−DSC thermal curves, cyclic voltammograms, lifetime curves, selected bond lengths and angles, intermolecular interactions, calculated transitions of Ir1-Ir5 in CH2Cl2 media and composition of the MOs and the assignment of different fragments. CIF files. See Herein, we have synthesized a series of 2',6'-difluoro-2,3'-bipyridine cyclometalating ligands by substituting electronwithdrawing (-CHO, -CF3, -CN) and electron-donating (-OMe, -NMe2) groups at the 4′ posiƟon of the pyridyl moiety and utilized for the construction of five new iridium(III) complexes (Ir1-Ir5) in the presence of picolinate as an ancillary ligand. The photophysical properties of the developed iridium(III) compounds were investigated with a view to understand the substituent effects. The strong electron-withdrawing (-CN) group containing iridium(III) compound (Ir3) exhibits highly efficient genuine green phosphorescence (λmax= 508 nm) at room temperature in solution and in thin film, with an excellent quantum efficiency (ΦPL) of 0.90 and 0.98, respectively. On the other hand, the -CF3 group substituted iridium(III) compound (Ir2) displays a sky-blue emission (λmax = 468 nm) with a promising quantum efficiency (ΦPL = 0.88 and 0.84 in solution and in thin film, respectively). The -CHO substituted iridium(III) complex (Ir1) showed greenishyellow emission (λmax = 542 nm). Most importantly, the strong electron-donating -NMe2 substituted iridium(III) complex (Ir5) gives a structureless and a broad emission profile in the wavelength region 450 to 700 nm (λmax = 520 nm) with a poor quantum efficiency. An intense blue phosphorescence with impressive quantum efficiency, especially in thin-film noted in the case of -OMe substituted iridium(III) complex (Ir4). Comprehensive density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches have been performed on the ground and excited states of the synthesized iridium(III) complexes, in order to obtain information about the absorption and emission processes and to gain deeper insights into the photophysical properties. The combinations of a smaller ΔES1-T1 and higher contribution of 3 MLCT in the emission process result in the higher quantum yields and lifetime values for complexes Ir1-Ir3. Multi-layered Phosphorescence Organic Light Emitting Diodes (PhOLEDS) were designed using the phosphorescent dopants Ir2, Ir3 and Ir4 and evaluated their elecroluminescence properties. The compound Ir4 at a doping level of 5 wt% shows the best performance with an external quantum efficiency of 4.7% , in nonoptimized device, and power efficiency of 5.8 lm W −1 , together with a true-blue chromacity CIEx,y = 0.15, 0.17 recorded at maximum brightness of 33,180 cd/m 2 . 28,[45][46][47][48][49][50][51] Accordingly, several groups have demonstrated that phosphorescence emission wavelengths can be tuned in t...