Objective: An eucalyptus essential oil-based nanoemulsion was produced and evaluated for its antimicrobial properties against Streptococcus mutans and its cytotoxicity in the surface mucous cells of rabbits. Methods: The essential oil-based nanoemulsion was synthesized with two species of eucalyptus—Eucalyptus citriodora and Eucalyptus globulus—followed by physicochemical characterization and the determination of antimicrobial activity and cell viability. Subsequently, the mouthwash formulations (fluoride and fluoride-free) were functionalized with the nanoemulsion, and their in vitro antimicrobial actions were evaluated against S. mutans. Results: The nanoemulsion presented an average particle size of around 100 nm, a polydispersity index close to 0.3, a zeta potential between −19 and −30 mV, a pH close to 7, a spherical shape, and a cell viability above 50%. The antimicrobial activity analysis showed that the nanoemulsion was effective in the control of S. mutans. The mouthwashes functionalized with the nanoemulsion also presented bacteriostatic and bactericidal properties. Conclusions: The bio-based material produced with eucalyptus essential oil presented adequate physicochemical characteristics, with the potential to be used as an innovative material in preventive dentistry, contributing to the maintenance of oral and systemic health.

Chromium(III) complexes [CrCl2(L)(THF)] based on monoanionic tridentate ligands [2a, L = {2-(C4H3N-2′-CH[double bond, length as m-dash]N)C2H4NHPh}; 2b, L = {5-tert-butyl-2-(C4H2N-2′-CH[double bond, length as m-dash]N)C2H3NHPh}; 2c, L = {2-(C4H3N-2′-CH[double bond, length as m-dash]N)C2H4OPh}] have been prepared. Complexes 2a and b were converted into the monomeric acetonitrile adducts [CrCl2(L)(NCMe)] [3a, L = {2-(C4H3N-2′-CH[double bond, length as m-dash]N)C2H4NHPh}; 3b, L = {5-tert-butyl-2-(C4H2N-2′-CH[double bond, length as m-dash]N)C2H3NHPh}] by reaction with acetonitrile at room temperature. All Cr complexes were characterized by IR spectroscopy, elemental analysis, magnetochemistry for 2a–c, and by X-ray crystallography for 3a and 3b. Upon activation with methylaluminoxane (MAO), chromium precatalysts 2a and 2c showed good activity in ethylene oligomerization (TOF = 47.0–57.0 × 103 (mol ethylene)(mol Cr)−1 h−1 at 80 °C), producing mostly oligomers (93.0–95.6 wt% of total products). On the other hand, under identical oligomerization conditions, 2b/MAO behaved as a polymerization catalyst generating predominantly polyethylene (73.0 wt%). However, the catalytic behavior of the precatalyst 2b can be adjusted by varying the MAO-to-Cr ratio. Thus, the use of 500 equiv. causes a dramatic shift from polymerization to ethylene oligomerization, eventually producing mainly lighter α-olefin fractions [α-C4 (68.7 wt%) and α-C6 (19.2 wt%)]. A further increase in the amount of MAO (1000 equiv.) leads to a more balanced distribution of oligomers, with a drastic decrease in the α-C4 and increase in the α-C8 fractions.

Cu(II) complexes bearing NNO-donor Schiff base ligands (2a, b) have been synthesized and characterized. The single crystal X-ray analysis of the 2a complex revealed that a mononuclear and a dinuclear complex co-crystallize in the solid state. The electronic structures of the complexes are optimized by Density Functional Theory (DFT) calculations. The monomeric nature of 2a and 2b species is maintained in solution. Antioxidant activities of the ligands (1a, b) and Cu(II) complexes (2a, b) were determined by in vitro assays such as 1,1-diphenyl-2-picrylhydrazyl free radicals (DPPH^.) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radicals (ABTS⁺). Our results demonstrated that 2a showed better antioxidant activity. MTT assays were performed to assess the toxicity of ligands and Cu(II) complexes in V79 cells. The antiproliferative activity of compounds was tested against two human tumor cell lines: MCF-7 (breast adenocarcinoma) and SW620 (colorectal carcinoma) and on MRC-5 (normal lung fibroblast). All compounds showed high cytotoxicity in the all-cell lines but showed no selectivity for tumor cell lines. Antiproliferative activity by clonogenic assay 2b showed a more significant inhibitory effect on the MCF-7 cell lines than on MRC-5. DNA damage for the 2b compound at 10 µM concentration was about three times higher in MCF-7 cells than in MRC-5 cells.

A series of new Ni(II) complexes of general formula {L}NiCl [Ni1, L = 2-(C4H3N-2′-CH[double bond, length as m-dash]N)C2H4NHPh; Ni2, L = 5-tert-butyl-2-(C4H2N-2′-CH[double bond, length as m-dash]N)C2H4NHPh; Ni3, L = 2-(C4H3N-2′-CH[double bond, length as m-dash]N)C2H4OPh; Ni4, L = 2-(C4H3N-2′-CH[double bond, length as m-dash]N)C6H4-2′-OPh; Ni5, L = 2-(C4H3N-2′-CH[double bond, length as m-dash]N)C6H4-2′-SPh; Ni6, L = 2-(C4H3N-2′-CH[double bond, length as m-dash]N)CH2C6H4-2′-OMe] were prepared and fully characterized. All nickel precatalysts, activated with methylaluminoxane (MAO), exhibited moderate to good activities for ethylene oligomerization [TOF = 6.1–71.3 × 103 mol (C2H4) (mol (Ni)−1 h−1)] and producing high selectivities for 1-butene (68.3–94.0 wt%). The catalytic performance was substantially affected by the ligand environment regarding the pendant oxygen- and sulfur-donor groups, and the substituents on the pyrrolide group. Activation of nickel precatalyst Ni3 with ethylaluminum sesquichloride (Et3Al2Cl3, EASC) instead of MAO produced a significantly more productive catalyst system than Ni2/MAO (TOF = 153 700 vs. 43 500 mol (C2H4) (mol (Ni)−1 h−1)); however, the 1-butene selectivity was drastically reduced, attaining only 53 wt% with a concomitant production of larger amounts of internal butenes (38 wt%). Under optimized conditions ([Ni] = 10 μmol, 30 °C, oligomerization time = 20 min, 20 bar ethylene, [Al]/[Ni] = 250), precatalyst Ni3 led to a TOF = 55 900 mol (C2H4) (mol (Ni)−1 h−1) and 82.8 wt% selectivity for 1-butene.