Structural and spectroscopic properties, solvation effects, intermolecular interactions, and biological assays of a Mn(II)-complex with 1,10-phenanthroline and chloro ligands

The bis(chloro)-bis(1,10-phenanthroline)-manganese(II) crystalline complex, with the formula [Mn(phen)₂Cl₂], was synthesized by slow evaporation method. Structural, thermal, and vibrational properties of the crystal were obtained by X-ray powder diffraction (XRPD), thermal analysis, Raman, and Fourier-transform infrared (FT-IR) spectroscopy. XRPD results showed that the crystal belongs to a monoclinic system with P2₁/c ($C_{2h}^5$) space group. Thermal analyses revealed that the material presents good stability within 300–558 K temperature interval. In addition, Hirshfeld surface analysis revealed the sites involved in intermolecular interactions predominant in the crystal. Also, all Raman and IR-active bands were assigned from computational calculations based on density functional theory (DFT) to analyze intramolecular vibration modes. Additionally, the electronic and vibrational properties were investigated considering three different media (vacuum, methanol, and water) using the integral equations formalism of the polarizable continuum model (IEFPCM). Lastly, the bactericidal assays on Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853) e Enterococcus faecalis (ATCC 25923) were carried out to evaluate the antimicrobial activity of this complex.