Thermal, morphological, and DFT studies on the scandium(III) sulfa drugs complexes

Four scandium(III) sulfa drug complexes were studied based on thermal, kinetic, morphological and computational investigations. The isolated solid complexes were synthesized by 1:2 molar ratios between scandium(III) chloride and four kinds of sulfa drugs; sulf-1 = sulfadimidine (1), sulf-2 = sulfanilamide (2), sulf-3 = sulfamethoxazole (3) and sulf-4 = sulfadiazine (4). The molecular formulae for the isolated complexes are [Sc(sulf-1)2(Cl)2]Cl (5), [Sc(sulf-2)2(Cl)2]Cl (6), [Sc(sulf-3)2(Cl)2]Cl (7) and [Sc(sulf-4)2(Cl)2]Cl (8). TGA thermograms for complexes (5-8) were utilized to study the different degradation steps. Moreover, the kinetic and thermodynamic functions have been calculated based on the data speculated for compounds (5-8). The surface morphology of (5-8) was studied by scanning electron microscopy (SEM). The compounds (5-8) exhibit favorable crystallinity, as X-ray powder diffraction (XRD) confirmed. The nano-scale of the samples was confirmed by the transmission electron microscopy (TEM) images. Furthermore, the DFT calculations for (1-8) were performed. The bond lengths for (5-8) are reduced or increased rather than that of free drug molecules due to complexation. Bond angles of compounds (5-8) predict the octahedral geometry (Oh) of Sc(III). The calculated vibrational spectra for compounds (5-8) were compared to the experimental IR, which may give quite differences attributed to different phases of measurement. KEY WORDS: Scandium, Sulfa-drugs, TGA, SEM, TEM, DFT, Coats-redfern, Complexes, Nano-particles Bull. Chem. Soc. Ethiop. 2025, 39(7), 1363-1380. DOI: https://dx.doi.org/10.4314/bcse.v39i7.10