Incredible colorimetric sensing behavior of pyrazole-based imine chemosensor towards copper (II) ion detection: synthesis, characterization and theoretical investigations

Herein, we synthesized more conjugated compounds like substituted fluorene, anthracene, and pyrene based pyrazole derivatives with good yield. All the compounds were thoroughly characterized by various spectral techniques such as NMR and mass analysis. Further, we studied the photophysical behavior of pyrazole de-rivatives (hybrids) upon the addition of analytes using UV-visible spectroscopic techniques. All the hybrid compounds were good colorimetric sensor for copper(II) ion. AS1, AS2 and AS3 hybrid compounds possess the limit of detections as 0.62 mu M, 0.47 mu M, and 4.4 mu M respectively. The binding constant of the hybrid compounds AS1, AS2 and AS3 were 3.1 x 10(-2) M, 3.9 x 10(-2 )M and 2.3 x 10(-2) M respectively. The detection limit and binding constant of anthracene based hybrid AS2 was superior when compared to AS1 and AS3. Further, ligand to the metal charge transition of the probe with analytes were confirmed by density function theory (DFT) through Gaussian 09 Software.

Automated summary

In this study, we synthesized substituted fluorene, anthracene, and pyrene based pyrazole derivatives with good yield and characterized them using various spectral techniques. We found that these compounds serve as good colorimetric sensors for copper(II) ions, with different detection limits and binding constants. Additionally, density functional theory confirmed the ligand to metal charge transition of the probe with analytes.