COMMUNICATIONand easy detection of luminescence signals, rational designs of luminescent materials that are sensitive to electrical stimuli are very important because of their promising applications for fabricating new-generation smart optoelectronic devices.Phosphorescent transition-metal complexes are an attractive candidate for stimuli-responsive luminescent materials due to their various charge-transfer excited states, including triplet metal-to-ligand charge transfer ( 3 MLCT), ligand-toligand charge transfer ( 3 LLCT), and intraligand charge transfer states. [ 33 ] These charge-transfer excited states are sensitive to external stimuli. Recently, we have reported an ionic phosphorescent Ir(III) complex [ppy 2 IrN ^ N] + PF 6 − (ppy, 2-phenylpyridine; N ^ N, 2-(2-pyridyl)benzimidazole) containing a polarizable N-H group in N ^ N ligand that displays interesting electrochromic luminescence from yellow to green near anode after applying a voltage. [ 34 ] This electrochromic luminescence is attributed to the generation of an internal electric fi eld caused by migration of anionic counterions under an applied electric fi eld, which leads to a change in excited-state properties of complex. Considering the ligand-dependent excited-state properties of Ir(III) complexes, it is very important to demonstrate whether the ECL performance can be tuned by changing the ligands of complexes and different luminescence-responsive modes to the electric fi eld can be realized, which are necessary for practical applications of the ECL materials.In this work, we designed and synthesized a series of ionic phosphorescent Ir(III) complexes [(C ^ N) 2 IrN ^ N] + PF 6 − ( Figure 1 , left) containing the same N ^ N ligand (2-(2-pyridyl)benzimidazole) and different C^N ligands, 2-(2,4-difl uorophenyl)pyridine (dfppy) for Ir1 , 2-( p -tolyl)pyridine (tpy) for Ir2 , 2-phenylquinoline (pq) for Ir3 , and 2-(thiophen-2-yl)quinoline) (tpq) for Ir4 . These complexes exhibited tunable ECL performance, and the effect of C ^ N ligands on the ECL performance was investigated in detail. The detailed synthetic routes of the complexes are given in Scheme S1 in the Supporting Information. The obtained complexes were characterized by nuclear magnetic resonance (NMR) and matrix-assisted laser desorption ionization time-of-fl ight mass spectrometry, cyclic voltammetry, UV/Vis absorption spectrometry, and steady-state and transientstate photoluminescence spectrometry Complexes Ir1 − Ir4 exhibit tunable emission colors from green to red in CH 3 CN solution (Figure 1 , middle), which are dependent on the C^N ligands. Their photophysical properties have been summarized in Table S1 in the Supporting Information. Next, we investigated their luminescence