Aggregation enhanced luminescent detection of homocysteine in water with terpyridine-based Cu2+ complexes

Four terpyridine-based Cu2+ complexes with different hydrophilic or hydrophobic groups were synthesized and developed for the detection of Hcy in water based on the aggregation of copper complexes. It is found that these terpyridine-based Cu2+ complexes were reduced by homocysteine (Hcy) along with generation of luminescent four-coordinated Cu+ species. Terpyridine-based Cu2+ complexes bearing hydrophilic groups such as [Ru(bpy)3](+) exhibited turn-on luminescence at 635 nm in the presence of Hcy and then the luminescence would be quenched in 1 min due to rapid oxidation of Cu+ species by dissolved oxygen in water, resulting in cyclic detection of Hcy. However, complexes bearing more hydrophobic groups exhibited stronger and much more durable luminescence over 10 min upon addition of Hcy in water because of aggregation of generated Cu+ species which were beneficial to enhance inhibition of oxygen-induced quenching. A 1500-fold luminescence intensity enhancement at 603 nm was observed in the detection of Hcy using the [Ir(ppy)(2)(bpy)](+) modified terpyridine-based Cu2+ complex. The detection process was fast within 2 min and limit of detection (LOD) was found to be similar to 10.1 nM. Finally, terpyridine-based Cu2+ complexes were successfully applied in cell imaging. (C) 2017 Elsevier B.V. All rights reserved.