Zwitterionic [4]helicene: a water-soluble and reversible pH-triggered ECD/CPL chiroptical switch in the UV and red spectral regions†
Abstract
The chiroptical switching properties of a readily accessible and water-soluble diaza [4]helicene are disclosed. This zwitterionic dye displays pH-dependent absorption and emission properties and this enables a reversible turn on/off of electronic circular dichroism at 300 nm and of circularly polarized luminescence in the red region upon protonation/deprotonation.