Synthesis, Spectroscopy Studies, and Theoretical Calculations of New Fluorescent Probes Based on Pyrazole Containing Porphyrins for Zn(II), Cd(II), and Hg(II) Optical Detection

New pyrazole–porphyrin conjugates were successfully prepared from a reaction of β-porphyrin–chalcone derivatives with phenylhydrazine in acetic acid followed by an oxidative step. This fast and efficient synthetic approach provided the expected compounds in yields up to 82%. The sensing ability of the new porphyrin–pyrazole derivatives to detect the metal ions Ag⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺, and Cr³⁺ was studied by spectrophotometric and spectrofluorimetric titrations. In the presence of Zn²⁺, the conjugates exhibit changes in the emission spectra that are desired for a ratiometric-type fluoroionophoric detection probe. The studies were extended to gas phase, where the pyrazole–porphyrin conjugates show ability to sense metal ions with high selectivity toward Cu²⁺ and Ag⁺, and in poly­(methyl methacrylate) doped films with promising results for Zn²⁺ detection