A bio-compatible pyridine-pyrazole hydrazide based compartmental receptor for Al 3+ sensing and its application in cell imaging.

For practical applications, the development of bio-compatible organic molecules as p-block ion chemosensors is critical. Herein, we report the single crystal (SC) of new pyridine-pyrazole derived Al ³⁺ sensor H2PPC [( Z )- N '-(2,3-dihydroxybenzylidene)-5-methyl-1-(pyridin-2-yl)-1 H -pyrazole-3-carbohydrazide] as well as its Cu-complex SC. The probe exhibits an "off-on" fluorescence response towards Al ³⁺ ions, and this has been modulated with different solvents. For selective detection of Al ³⁺ ions, a special coordination pocket in the structural backbone is advantageous. The chemosensor exhibits a submicromolar detection level (LOD = 4.78 μM) for Al ³⁺ . The density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations of H2PPC and [Al(HPP)2]+ (1) reveal that a change of the structural conformation of probe H2PPC upon complexation causes the pyrazole and pyridine units to create a specific cavity to tether Al ³⁺ , and consequently H2PPC proves to be a promising molecule for Al ³⁺ detection. Furthermore, the probe has been successfully used to evaluate Al ³⁺ as a low-cost kit using filter paper strips, and the in situ Al ³⁺ ion imaging in Vero cells as well as A549 cell lines shows the sensor's nuclear envelope penetrability, indicating that it has great potential for biological and environmental applications.