Synthesis of Oxadiazole Hybrids as Dual-Functional Solvatochromic Fluorophores: Integrated Photophysical, DFT, Security Ink, and In Silico Breast-Cancer Target Prediction Studies

Two new phenothiazine–oxadiazole hybrids, FPZ-1 and CPZ- 1, were designed, synthesized, and evaluated as dual-functional solvatochromic fluorophores and in silico breast-cancer target prediction. The molecular design integrates an electron-rich N-phenylphenothiazine donor with an electron-deficient 1,3,4-oxadiazole/triazole acceptor framework, enabling intramolecular charge-transfer behavior and polarity-responsive emission. The target compounds were obtained through hydrazone formation followed by KMnO 4 -mediated oxidative cyclization, affording CPZ-1 and FPZ-1 in good yields. Their structures were confirmed by FT-IR, 1 H NMR, 13 C NMR, and elemental analysis. Solvent-dependent photophysical studies revealed clear positive solvatochromism, with FPZ-1 showing absorption/emission shifts from 370/450 nm in cyclohexane to 382/493 nm in DMSO, while CPZ-1 shifted from 364/449 to 374/485 nm. The Stokes shifts increased with solvent polarity, reaching 5894 cm −1 for FPZ-1 and 6119 cm −1 for CPZ-1 in DMSO, confirming stabilization of a polar charge-transfer excited state. DFT and TD-DFT calculations supported the donor–acceptor electronic architecture, showing HOMO localization mainly over the phenothiazine donor and LUMO distribution over the oxadiazole–triazole acceptor region. CPZ-1 exhibited stronger excited-state polarization due to the carboxyl substituent, whereas FPZ-1 showed slightly red-shifted optical transitions associated with the fluorophenyl group. The intense UV-responsive fluorescence and large Stokes shifts enabled application of the compounds as invisible security inks for anti-counterfeiting and information encryption. Network pharmacology identified breast-cancer-related target intersections, with HSP90AA1, EGFR, ESR1, and BCL2L1 emerging as key hub proteins. Molecular docking further supported favorable interactions of the compounds with selected cancer-associated targets.