Aggregation‐Induced Electrochemiluminescence and Nitric Oxide Recognition by Halogen Bonding with a Ruthenium(II) Complex

In this study, a new strategy for NO detection based on the aggregation-induced electrochemical luminescence (AIECL) of a ruthenium-based complex and the halogen bonding effect was developed. First, [Ru(phen)2 (phen-Br2 )]2+ (phen : 1,10-phenanthroline, phen-Br2 : 3,8-dibromo-1,10-phenanthroline) was synthesized and exhibited aggregation-induced emission (AIE) and AIECL properties in a poor solvent (H2 O). [Ru(phen)2 (phen-Br2 )]2+ exhibited greatly enhanced AIECL properties compared to its AIE intensity. When the volume fraction of water (fw , v %) in the H2 O-acetonitrile (MeCN) system was increased from 30 to 90 %, the photoluminescence and electrochemiluminescence (ECL) intensities were three- and 800-fold that of the pure MeCN system, respectively. Dynamic light scattering and scanning electron microscopy results indicated that [Ru(phen)2 (phen-Br2 )]2+ aggregated into nanoparticles. AIECL is sensitive to NO because of its halogen bonding effect. The C-Br⋅⋅⋅N bond between [Ru(phen)2 (phen-Br2 )]2+ and NO increased the distance of complex molecules, resulting in ECL quenching. A detection limit of 2 nM was obtained with 5 orders of magnitude linear range. The combination of the AIECL system and the halogen bond effect expands the theoretical research and applications in biomolecular detection, molecular sensors, and stages of medical diagnosis.