Mixed ligand approach for novel hydrazide copper (II) complexes: Structural aspects, theoretical investigation and their biological evaluation

In this paper, two novel Cu(II) complexes [CuL(S-1-amino-2-propanol)] (R1) and [CuL(S-2-amino-1-propanol)] (R2) have been synthesized and characterized using Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), high-resolution mass spectrometry (HR-MS), scanning electron microscopy (SEM) and single crystal X-ray diffraction (SCXRD) technique. The single-crystal XRD analyses show that compounds R1 and R2 crystallized in triclinic and monoclinic crystal systems with P-1 and P2(1) space groups, respectively. The tau 5 parameter values of R1 and R2 confirmed distorted square pyramidal geometry around Cu(II) centre. The compounds R1 and R2 possess 2D polymeric chains with (4,4)IIIa and 2C1 topology, respectively. The non-covalent interactions and electrostatic properties were investigated using Hirshfeld surface analysis and density functional theory (DFT). DFT calculations revealed higher stability of R1 over R2. The presence of strong hyper conjugative interactions in carbon-carbon and carbon-nitrogen bonds has been confirmed by natural bond orbital (NBO) analysis. Time-dependent (TD)-DFT calculations were also performed to determine the excited state properties. Based on theoretical calculations, the simulated spectra showed absorption maxima at 506 and 743 nm for both complexes. Antimicrobial assays revealed that R1 is significantly antimicrobial against Pseudomonas aeruginosa at 512 and 256 mu g/mL for Staphylococcus aureus, correspondingly. Serum binding studies of R1 confirm the existence of instinctive bonding interactions due to negative values on account of increment G, increment S and increment H obtained from thermodynamics studies. In silico molecular dynamics and docking approaches have been used to validate the experimental findings of anti-microbial assay and serum binding studies. A high dock score for R1 over R2 revealed the high binding energy of the former with bacterial protein. It was found that the protein-ligand complex remained stable throughout the dynamic simulation process, and substantial interactions between R1 and bovine serum albumin were observed.