Synthesis, photophysical properties and electrochemiluminescence performances of a series of cationic iridium(III) complexes

• Four new cationic iridium complexes have been prepared.
• The photophysical influence of the 4-substituents has been investigated.
• The ECL intensity of iridium(III) complex 1 is 3.8 times of Ru(bpy)32+.
• The single crystal structure of complex 4 had been measured.

A series cationic cyclometalated iridium(III) complexes, ([Ir(pq)2(bpy)][PF6] (1), [Ir(dpq)2(bpy)[PF6] (2), [Ir(pqcm)2(bpy)][PF6] (3), [Ir(pqca)2(bpy)][PF6] (4), pqH = 2-phenyl-quinoline, dpqH = 2,4-diphenyl-quinoline, pqcmH = 2-phenyl-quinoline-4-carboxylic acid methyl ester, pqcaH = 2-phenyl-quinoline-4-carboxylic acid adamantanemethyl ester, bpy = 2,2′-bipyridine), have been synthesized. New iridium(III) complexes had been characterized by the NMR and mass spectroscopies, and the single crystal structure of complex 4 had been measured. In CH3CN solution, the iridium(III) complexes 1 and 2 showed yellow emission at 560 nm, while the iridium(III) complexes 3 and 4 displayed pure red emission at 620 nm. The iridium(III) complexes had quantum efficiencies between 1.1% and 8.5%. The electrochemiluminescence (ECL) of cationic cyclometalated iridium complexes was investigated in CH3CN/H2O (40:60 (v/v)) with Au electrode as working electrode. The ECL peaks were obtained when tri-n-propylamine was used as co-reactant and positive initial potential scan direction was adopted. The ECL intensity of iridium(III) complex 1 is 3.8 times of Ru(bpy)32+. The phosphorescence quantum efficiencies of complex 1 and Ru(bpy)32+ are close, so the better ECL performance suggests that iridium complexes have great application potential in ECL detection. The ECL intensities of iridium(III) complexes had almost the same sequence with the quantum efficiencies of iridium(III) complexes.

A series cyclometalated iridium(III) complexes ([Ir(pq)2(bpy)][PF6] (1), [Ir(dpq)2(bpy)[PF6] (2), [Ir(pqcm)2(bpy)][PF6] (3), [Ir(pqca)2(bpy)][PF6] (4), had been synthesized. The electrochemiluminescence (ECL) of cationic cyclometalated iridium complexes, was investigated with Au electrode as working electrode. The ECL peaks were obtained when tri-n-propylamine was used as co-reactant. The ECL intensity of iridium(III) complex 1 is 3.8 times of Ru(bpy)32+ though their phosphorescence quantum efficiencies are close, suggesting that iridium complexes have great application potential in ECL detection. The ECL intensities of iridium(III) complexes had almost the same sequence with the quantum efficiencies of iridium(III) complexes.Figure optionsDownload as PowerPoint slide