2-Nitro- and 4-fluorocinnamaldehyde based receptors as naked-eye chemosensors to potential molecular keypad lock.

New-generation chemosensors desire small organic molecules that are easy to synthesise and cost-effective. As a new interdisciplinary area of research, the integration of these chemosensors into keypad locks or other advanced communication protocols is becoming increasingly popular. Our lab has developed new chemosensor probes that contain 2-nitro- (1-3) and 4-fluoro-cinnamaldehyde (4-6) and applied them to the anion recognition and sensing process. Probes 1-6 are colorimetric sensors for naked-eye detection of AcO-/CN-/F-, while probes 4-6 could differentiate between F- and AcO-/CN- anions in acetonitrile. Using the density functional theory (DFT), it was found that probes 1-6 acted as effective chemosensors. By using Probe 5 as a chemosensor, we explored colorimetric recognition of multiple anions in more detail. Probe 5 was tested in combination with a combinatorial approach to demonstrate pattern-generation capability and its ability to distinguish among chemical inputs based on concentration. After pattern discrimination using principal component analysis (PCA), we examined anion selectivity using DFT computation. In our study, probe 5 demonstrates excellent performance as a chemosensor and shows promise as a future molecular-level keypad lock system.