Green and Blue Electrochemically Generated Chemiluminescence from Click Chemistry-Customizable Iridium Complexes

• Published in: Chemistry : a European journal 2011-04, Vol.17 (16), p.4640-4647
• Main Authors: Zanarini, Simone, Felici, Marco, Valenti, Giovanni, Marcaccio, Massimo, Prodi, Luca, Bonacchi, Sara, Contreras-Carballada, Pablo, Williams, Rene M., Feiters, Martin C., Nolte, Roeland J. M., De Cola, Luisa, Paolucci, Francesco
• Format: Article
• Language: English
• Subjects: Buffer solutions; Cationic; Chemiluminescence; Chemistry; click chemistry; cyclic voltammetry; electrochemiluminescence; Emission; Investigations; iridium; Iridium compounds; Ligands; Modulation; N ligands; Solubility
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201002956

Cationic cyclometalated iridium complexes containing two anionic phenylpyridine (ppy) ligands and the neutral bidentate triazole–pyridine ligand, 2‐(1‐substituted‐1H‐1,2,3‐triazol‐4‐yl)pyridine (pytl), were investigated. The complexes display a rich and reversible electrochemical behavior, upon investigations by cyclic voltammetry in strictly aprotic conditions, that couples with excellent emission quantum yields and long lifetimes of the excited states. Therefore, in organic media, all complexes have generated intense green electrochemiluminescence (ECL) through the so‐called annihilation procedure and, importantly, a modulation of the emission energy (to blue) has been easily obtained by simple fluorination of the ppy ligand. Finally, taking advantage of their remarkable solubility in water, intense ECL was also obtained from aqueous buffer solutions using the co‐reactant method, thus making all the investigated complexes highly promising for their effective use as ECL labels in bioanalytical applications. Tune the colors! Thanks to their excellent photophysical and electrochemical properties, cationic phenylpyridine cyclometalated iridium complexes, containing a triazole–pyridine ligand, generate intense green electrochemiluminescence (ECL) in organic solvents and in water. Fluorination of the ligand allows for the easy and effective modulation of emission to blue (see graphic).