Tailoring the sensing behaviors to Zn2+ and AIEE properties of phenanthroline derivatives through isomer engineering.

Three isomeric phenanthroline compounds, namely 2-DP, 3-DP and 5-DP, are constructed by incorporating 4-(2,2-diphenyl-vinyl)-phenyl unit into 2-, 3-, and 5-positions of phenanthroline. This approach functionalizes these compounds to exhibit different solvatochromism effects and metal-ion sensing abilities. 2-DP shows no obvious sensitivity for proton solvent and metal ions, but it's quite the opposite for 3-DP and 5-DP. Significantly, 3-DP possesses higher selectivity and sensitivity to Zn 2+ than 5-DP to Zn 2+ , with a limit of detection down to 10 −8  M. The density function theory calculations reveal that their different sensing behaviors are related to their steric hindrance and electronic effects. Moreover, 2-DP, 3-DP and 5-DP all exhibit aggregation-induced enhanced emission (AIEE), in which the photoluminescence (PL) enhancement of 2-DP is the biggest in aggregated state. It is thought that the molecule torsion degree is responsible for their different AIEE behaviors, which is supported by the X-ray structural analysis. The isomer engineering for phenanthroline provides a simple method to enhance the selectivity and sensitivity to metal ions, and to optimize solid-state luminescence properties. [ABSTRACT FROM AUTHOR]