The goal of this study is to synthesize, determine the structure, and examine the antimicrobial properties of novel Cu(II) and Au(III) complexes of 2,4-dithiouracil and its derivatives. These complexes were obtained by mixing aqueous solutions of the corresponding metal salts with the ligand dissolved in DMSO and aqueous NaOH, using a metal-to-ligand ratio of 1:4:2. The structures of the new compounds were analyzed by melting point determination, microwave plasma atomic emission spectrometry (MP-AES) for Cu and Au, inductively coupled plasma optical emission spectrometry (ICP-OES) for S, attenuated total reflection (ATR), solution and solid-state NMR, and Raman spectroscopy. The data for 2,4-dithiouracil obtained from the ¹H NMR, ¹³C NMR, distortionless enhancement by polarization transfer spectrum (DEPT-135), proton–proton homonuclear correlation spectrum (¹H-¹H COSY), long-range ¹H-¹³C heteronuclear multiple bond correlation experiment (HMBC), and heteronuclear single quantum coherence spectra (HSQC) aided the interpretation of the NMR data for the gold and copper complexes. Furthermore, the antimicrobial effect of the free ligands and their complexes was assessed against Gram-positive and Gram-negative bacteria, as well as yeasts.

A periodic study of engine oil can allow one to anticipate possible breakdowns that a vehicle could have. Due to the complexity of the matrix of this type of sample, a sample treatment prior to analysis is necessary. Analytical chemistry is constantly searching for simpler, more sensitive and environmentally friendly methods. The reversed phase dispersive liquid–liquid microextraction fulfills all the characteristics for the analysis in this type of sample by microwave induced plasma optical emission spectrometry (MIP OES). In this work, the extractant solvent used for the microextraction procedure is a diluted acid solution (i.e., 3 M HCl), which is a less-hazardous solvent, in comparison with other solvents used in microextraction procedures. Besides, it is perfectly compatible with MIP OES. The main experimental factors affecting the extraction of Cr, Cu, Mn, Mo, and Ni (i.e., amount of sample, extractant type, acid concentration, extractant volume, extractant time, and centrifugation time and speed) are optimized using a multivariate analysis consisting of two steps: a Plackett–Burman design followed by a circumscribed central composite design. Under optimum conditions (i.e., amount of sample: 5.9 g; extractant volume: 60 μL; extractant type: HCl; acid concentration: 3 M; extraction time: 3 min; centrifugation time: 3 min; centrifugation speed: 2000 rpm), the proposed analytical method is validated and employed to analyze different samples (i.e., used and unused engine oils). Two calibration methods have been evaluated since matrix effects have been observed in the used engine oil sample. These effects have been eliminated using standard addition calibration obtaining RSD and recovery values in the range of 4–12% and 94–106%, respectively, for samples spiked with 1 μg g⁻¹ of Cr, Cu, Mn, Mo and Ni. Finally, the greenness of this method has been assessed by the Eco-Scale metrics.

New hyphenation of a continuous flow photochemical vapor generator (PVG) to a modified multimode sample introduction system (MSIS) used as a gas–liquid separator and microwave plasma atomic emission spectrometry (MP-AES) was proposed for the analysis of trace mercury. The widened MSIS bottom inlet contributes to an increase in Hg⁰ mass transfer in the gas–liquid separator, allowing mercury determination by MP-AES. After optimizing the PVG reactor conditions and MP-AES instrument parameters, a limit of detection (LOD) of 0.25 ppb was obtained for Hg²⁺. The applicability of the PVG-MSIS-MP-AES method was subsequently demonstrated for trace mercury analysis in two soil CRMs – ERM-CC135a (Contaminated Brickworks soil) and CRM005 (Sewage Amended soil).

A combination of 1D and 2D NMR techniques, including HMQC, HSQC, ¹H-¹H COSY and HMBC, was used to provide completely assigned ¹H and ¹³C NMR data for the structures of three 3-[substituted methylidene]-1H,3H-naphtho[1,8-cd]-pyran-1-ones—3-[(4-methoxyphenyl)methylidene]-1H,3H-naphtho[1,8-cd]-pyran-1-one, 3-[(4-fluorophenyl)methylidene]-1H,3H-naphtho-[1,8-cd]-pyran-1-one and 3-[(thiophen-3-yl)methylidene]-1H,3H-naphtho[1,8-cd]-pyran-1-one. The heteronuclear coupling constants ^1–4J_CF and ^3–4J_HF were correspondingly determined. Additionally, IR and Raman spectral data were provided in support of the assigned structures.

The structure verification of 5′-oxospiro-(fluorene-9,4′-imidazolidine)-2′-thione by NMR is reported. Toward this aim, 2D NMR techniques including ¹H-¹H COSY, HMQC, and HMBC experiments were used to assist with the assignment of the ¹H and ¹³C chemical shifts for the corresponding structure. The mutual interpretation of the 1D and 2D NMR spectra ensured a complete and accurate ¹H and ¹³C NMR data assignment for 5′-oxospiro-(fluorene-9,4′-imidazolidine)-2′-thione.

The structure of spiro-(fluorene-9,4’-imidazolidine)-2’,5’-dithione was verified by 1D (¹H, ¹³C, DEPT 135) and 2D NMR (¹H-¹H COSY, HMQC and HMBC) spectroscopy. Additionally, the completely assigned NMR data was supported by Raman band assignments. HOSE predictions were incorporated by using the open-access NMRShiftDB database for verification of the assigned ¹³C NMR chemical shifts.