فهرست نشریات علمی دسترسی آزاد ایران

A new family of nanocrystalline copper(II) bis(keto-imino) complexes bearing the chlorinated Schiff-base ligand (Z)-ethyl 4-chloro-3-(phenylimino)butanoate (EClN) was synthesized and structurally characterized at the nanoscale. The parent complex CuEClN was prepared by condensation of EClN with copper(II) acetate, then five-coordinate adducts CuEClN-py, CuEClN-bpy, CuEClN-C₁V⁺.PF₆⁻ and CuEClN-V₂²⁺.2PF₆⁻ were obtained through axial coordination of pyridine, 4,4ʹ-bipyridine, mono-methyl viologen hexafluorophosphate (C₁V⁺.PF₆⁻) and propylene-bridged bis-viologen bis(hexafluorophosphate) (V₂²⁺.2PF₆⁻). The compounds were identified by FT-IR, LC-MS, UV-Visible and TGA analyses. Powder X-ray diffraction confirmed the crystalline character of every compound, and crystallite sizes were quantified in the nanoscale (range ≈ 6 – 81 nm) by both Scherrer and Williamson–Hall (W–H) models. The W–H analysis simultaneously delivered the lattice-strain (ε) and revealed that bulky charged axial viologens generate the strongest distortion (ε = 1.56 × 10⁻³ for CuEClN-V₂²⁺.2PF₆⁻), whereas the small, flexible parent ligand EClN gives the most ordered lattice. FE-SEM micrographs corroborated the XRD trend: chlorinated viologen complexes display sub-10 µm aggregates with finer secondary particles. UV-Visible spectra in DMF/DMSO show the d–d transitions expected for square-planar (CuEClN) and square-pyramidal (adducts) geometries. Chemical reduction of the viologen-bearing complexes by activated zinc and electrochemical reduction by cyclic voltammetry in DMF (under Ar) furnished, respectively, intermolecular π-dimers (CuEClNC₁V•)₂ and an intramolecular bis-viologen π-dimer within CuEClNV₂, monitored by characteristic absorption bands at ≈ 380 nm and ≈ 554–560 nm. The reversibility upon air re-oxidation establishes these nanocrystalline complexes as redox-triggered molecular switches and promising candidates for nano-electronic and smart-material applications.