pH-Dependent Chromogenic and Smartphone-Assisted Detection of Fe(III) by Acid-Sensitive 1,2-Biphenyl-Substituted Benzimidazole 1,2,3-Triazole Hybrids: In Vitro Anticancer Property Evaluation and In Silico Inhibition of Breast Cancer Estrogen Receptor Mutant L536S

The detection of Fe(III) ions and monitoring of pH conditions are vital for safety, efficiency, and sustainability in scientific research, environmental management, and industrial applications. In this study, two 1,2-biphenyl-substituted benzimidazole-1,2,3-triazole hybrids, Pact and Oact, were designed, developed, and characterized by various spectroscopic techniques including single-crystal XRD analysis. Pact demonstrated high sensitivity and selectivity towards Fe(III) ions under physiological pH, confirmed through visual tests, UV–visible, and fluorescence spectroscopy, with detection limits (LOD) of 0.3 (emission) and 0.07 nM (absorption). A 1:1 ligand-to-metal binding ratio was established by Job's plot and supported by NMR, mass, VSM, and FT-IR analyses. RGB tool detection (LOD: 3.4 mM) and a paper kit test confirmed its portable and reversible nature, validated by EDTA tests, suggesting potential for molecular logic gate applications. Environmental monitoring potential was highlighted through real water sample analysis, while DFT calculations identified favorable metal binding sites. Additionally, Pact exhibited pH sensitivity in highly acidic conditions, while Oact, containing a nitro group, showed superior in vitro anticancer activity against HeLa cells compared to Pact, supported by a higher binding score (−9.10 kcal/mol vs. −8.63 kcal/mol) in molecular docking studies against the breast cancer estrogen receptor mutant L536S (PDB ID: 6sbo). Antioxidant assays further demonstrated Oact's enhanced radical scavenging potential.