Synthesis, characterization, crystal engineering, DFT, and biological evaluation of a novel Cu(II)-perchlorate Schiff base complex.

Today's crystal engineering in coordination chemistry community offers diverse applications and innovative bonding concepts in crystal assembly. The current research delves into synthesizing one novel Cu(II) complex, [(NO₃)Cu(H₂O)(L^2,2-Me2)(μ-H₂O)Cu(L^2,2-Me2)](H₂O)ClO₄ (L^2,2-Me2 = Schiff base) with NaClO₄. A combination of standard spectroscopic methods, including SEM-EDX, XPS, and SCXRD (single-crystal X-ray diffraction) study, was used to characterize the complex. The X-ray structure reveals that the di-nuclear Cu(II) complex crystallizes in the triclinic space group P-1, and the crystal assembly is stabilized predominantly by C-H···π interactions, as well as hydrogen bonding interactions such as N-H⋯O and O-H⋯O. A comprehensive DFT analysis, a hallmark of our research, explored the complex semiconductors and sensing capabilities for cations (Co²⁺/Ni²⁺/Cd²⁺) and anions (Br^-/I^-), providing valuable insights into the ECT (Electronic Charge Transfer) processes within the complex. MEP surface and FMO energy gap support the complex sensing and semiconductor behaviour. Antimicrobial screening reveals comparable activity for the Schiff base and its Cu(II) complex against both Gram +ve/-ve bacterial and fungal strains based on zone of inhibition (ZOI) and minimum inhibitory concentration (MIC). Meanwhile, the in vitro anticancer activity of the Cu(II) complex was assessed using the Trypan blue exclusion and MTT methods on the HepG2 and H9c2 cancer cell lines. The IC₅₀ value indicates that the Cu(II) complex exhibits significant anticancer activity. The structure-activity relationship (SAR) through the chelation/Tweedie's polarization theory, complex geometry, hydrogen bond-type supramolecular interactions, the redox role of Cu(II) metal ions, and the generation of reactive oxygen species (ROS) by Cu(II) metal ions, which adequately explain the biological activity of the complex. Subsequently, the complex was utilized for potential applications in sensors or therapeutics, and combined DFT and biological findings underscore the novel research on the Cu(II) complex.