Structural, molecular orbital and optical characterizations of solvatochromic mixed ligand copper(II) complex of 5,5-Dimethyl cyclohexanate 1,3-dione and N,N,N′,N′N″-pentamethyldiethylenetriamine

• Molecular orbital calculations were accomplished using Hyperchem 7.52 for the ligand and its complex.
• XRD analysis is used to estimate the microstructural quantities based on the conventional W–H plot.
• Optical parameters of Cu(DMCHD)(Me5dien)NO3 were calculated.
• The optical band gap is determined based on the applicability of the band theory.

In this work, a new solvatochromic mononuclear mixed ligand complex with the formula, Cu(DMCHD)(Me5dien)NO3 (where, DMCHD = 5,5-Dimethyl cyclohexanate 1,3-dione and (Me5dien) = N,N,N′,N′N″-pentamethyldiethylenetriamine was synthesized and characterized by analytical, spectral, magnetic, molar conductance, thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and transmission electron microscope (TEM) measurements. The formation constant-value for copper (II)-DMCHD was found to be much lower than the expected for similar β-diketones, revealing monobasic unidentate nature of this ligand. The d–d absorption bands of the prepared complex exhibit a color changes in various solvent (solvatochromic). Specific and non-specific interactions of solvent molecules with the complex were investigated using Multi Parametric Linear Regression Analysis (MLRA). Structural parameters of the free ligands and their Cu (II) – complex were calculated on the basis of semi-empirical PM3 level and compared with the experimental data. The crystallite size and morphology of Cu(DMCHD)(Me5dien)NO3 were examined using XRD analysis and TEM, revealing that the complex is well crystalline and correspond to the monoclinic crystal structure. The lattice strain and mean crystallite size were estimated by Williamson–Hall (W–H) plot using X-ray diffraction data. The main important absorption parameters such as extinction molar coefficient, oscillator strength and electric dipole strength of the principal optical transitions in the UV–Vis region were calculated. The analysis of absorption coefficient near the fundamental absorption edge reveals that the optical band gaps are direct allowed transitions with values of 2.78 eV and 3.59 eV. The present copper (II) complex was screened for its antimicrobial activity against Staphylococcus Aureus and Bacillus Subtilis as Gram-positive bacteria, Escherichia Coli and Salmonella Typhimurium as Gram-negative bacteria and Candida Albicans as fungus strain.

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