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In the present manuscript, three different 4,7-dihydroxycoumarin derivatives were prepared and structurally characterized by crystallographic and spectroscopic techniques in combination with the B3LYP-D3BJ theoretical method. Cytotoxic and antimicrobial activities of investigated compounds were screened against different cell lines and microorganisms. HCT-116 cells were most sensitive to the 3-(1-(2-hydroxyphenyl)amino) ethylidene)-2,4-dioxochroman-7-yl acetate derivative, while the best antimicrobial activity against Bacillus subtilis ATCC 6633 was shown by 3-(1-(2-hydroxyphenyl)amino)ethylidene)-2,4-dioxochroman-7-yl acetate. The molecular docking study for all compounds with important epidermal growth factor receptors (EGFR) was performed. The results indicate that the largest contribution to the binding energy is through conventional hydrogen bonds.

Ruthenium complexes have gained significant attention due to the ruthenium similarity to iron, lower toxicity, and higher anticancer effectiveness than other compounds. In this contribution, five new isonicotinate-polyethylene glycol ester ligands were synthesised and characterised by NMR and IR spectroscopies. The corresponding Ru(II) complexes were also obtained, and their structure was investigated by traditional methods. The optimisation of structures was performed at B3LYP/6-31+G(d,p) level of theory for H, C, N and O atoms and B3LYP/LanL2DZ for Ru. The intramolecular stabilisation interactions were assessed through the natural bond orbital approach. The NMR chemical shifts were predicted by the gauge independent atomic orbital method and compared to the experimental values. High correlation coefficients and low mean absolute errors between these data sets proved that the predicted structures described well the experimental ones. The theoretical and experimental IR spectra were also compared, and differences in the most notable bands were described. One of the ligands (L5) and complexes (5) showed fluorescent properties due to methylisatoic moiety. The electronic spectra of this compound were modelled by the time dependent-density functional theory method. The difference of 11 nm between the experimental and the theoretical wavelength was explained by the interactions between the solvent and the solute. Further biological and theoretical studies are advised for this series of compounds.

Organotin(IV) compounds show great potential as antitumor metallodrugs with lower toxicity and higher antiproliferative activity. Histone deacetylases (HDAC) inhibitors are characterised by high bioavailability and low toxicity. In this research, the two novel octahedral organotin(IV) complexes of physiologically active hydroxamate-based ligands, N-hydroxy-4-phenylbutanamide (HL1) and N-hydroxy-2-propylpentanamide (HL2), have been prepared and characterized using FTIR, 1H-, 13C- and 119Sn-NMR spectroscopy. Particular emphasis was put on the binding characteristics of ligands. The structures were additionally analysed by the density functional theory at B3LYP-D3BJ/6- -311++G(d,p)(H,C,N,O)/LanL2DZ(Sn) level. The theoretical IR and NMR spectra were compared to the spectroscopic data, and it was concluded that the predicted structures described well the experimental ones. The stability of different isomers of HL1 and HL2 was assessed by the natural bond orbital analysis, and the importance of intramolecular hydrogen bond was outlined. The interactions between donor atoms and Sn were investigated and correlated with the changes in chemical shift and the wavenumbers of characteristic vibrations.

The antiradical activity of L-3,4-dihydroxyphenylalanine (L-DOPA), dihydroxyphenylacetic acid (DOPAC), homovanillic acid and tyrosine towards 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt radical (ABTS-) was investigated experimentally and theoretically by UV–Vis spectroscopy and the DFT theory. The importance of the catechol moiety for this reaction was proven due to the formation of intramolecular hydrogen bond in the formed anions and radicals. The results indicated L-DOPA and DOPAC were more potent radical scavengers than homovanillic acid and tyrosine just because of intramolecular hydrogen bond formation. Based on experimental spectra, it was proved that electron transfer led to the reduction of ABTS•-. The values of thermodynamic parameters were used to predict the preferred mechanism. The reaction rates were calculated for the electron transfer processes and it was shown that these were both kinetically and thermodynamically driven processes. Based on the reaction rate values, thermodynamic parameters, and present species, as determined by electronic spectra, it was concluded that single proton loss electron transfer (SPLET) is the dominant reaction mechanism in the investigated system. [Projects of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172040 and Grant no. 172015]