This work describes the use of simple zinc(II) salts (ZnCl₂, ZnCO₃, Zn(OAc)₂, ZnO, Zn(ClO₄)₂, Zn(TfO)₂, and Zn(BF₄)₂) as effective catalysts for the esterification of fatty acids with long-chain alcohols and simple polyols through a homogeneous system that allows the gradual and selective removal of water. The results show that the catalytic activity depends on the nature of the counterion: the most effective are the salts with poorly coordinating anions (perchlorate and triflate) or containing basic Brønsted anions (oxide, acetate, and carbonate). However, only with the latter is it possible to fully recover the catalyst at the end of each run, which is easily filtered in the form of zinc carboxylate, given its insolubility in the ester produced. In this way, it is possible to recycle the catalyst numerous times, without any loss of activity. This beneficial prerogative couples the efficiency of the homogeneous catalysis with the advantage of the heterogeneous catalysis. The process is, therefore, truly sustainable, given its high efficiency, low energy consumption, ease of purification, and the absence of auxiliary substances and byproducts.

The growing production of biodiesel as a promising alternative and renewable fuel led as the main problem the dramatic increase of its by-product: glycerol. Different strategies for glycerol derivatization have been reported so far, some more efficient or sustainable than others. Herein, we report a very promising and eco-friendly transformation of glycerol in nontoxic solvents and chemicals (i.e., solketal, ketals), proposing three new families of Fe(III) compounds capable of catalysing glycerol acetalization with unpublished turn over frequencies (TOFs), and adhering most of the principles of green chemistry. The comparison between the activity of complexes of formula [FeCl₃(1-R)] (1-R = substituted pyridinimine), [FeCl(2-R,R′)] (2-R,R′ = substituted O,O′-deprotonated salens) and their corresponding simple salts reveals that the former are extremely convenient because they are able to promote solketal formation with excellent TOFs, up to 10⁵ h^–1. Satisfactory performances were shown with respect to the entire range of substrates, with results being competitive to those reported in the literature so far. Moreover, the experimental activity was supported by an accurate and complete ab initio study, which disclosed the fundamental role of iron(III) as Lewis acid in promoting the catalytic activity. The unprecedented high activity and the low loading of the catalyst, combined with the great availability and the good eco-toxicological profile of iron, foster future applications of this catalytic process for the sustainable transformation of an abundant by-product in a variety of chemicals.

Octahedral Pt(IV) complexes (2Pt–R) containing a glycoconjugate carbene ligand were prepared and fully characterized. These complexes are structural analogues to the trigonal bipyramidal Pt(II) species (1Pt–R) recently described. Thus, an unprecedented direct comparison between the biological properties of Pt compounds with different oxidation states and almost indistinguishable structural features was performed. The stability profile of the novel Pt(IV) compounds in reference solvents was determined and compared to that of the analogous Pt(II) complexes. The uptake and antiproliferative activities of 2Pt–R and 1Pt–R were evaluated on the same panel of cell lines. DNA and protein binding properties were assessed using human serum albumin, the model protein hen egg white lysozyme, and double stranded DNA model systems by a variety of experimental techniques, including UV–vis absorption spectroscopy, fluorescence, circular dichroism, and electrospray ionization mass spectrometry. Although the compounds present similar structures, their in-solution stability, cellular uptake, and DNA binding properties are diverse. These differences may represent the basis of their different cytotoxicity and biological activity.

The growing global demand for renewable energy sources can be reached using biofuels such as biodiesel, for example. The most used route to produce biodiesel is the transesterification reaction of oils or fats with short-chain alcohols, generating fatty acid esters (biodiesel) and a very important by-product, glycerol (Gly). Gly is widely used in different sectors of the industry, and in order to add value to this by-product, heterogeneous catalysis becomes a relevant tool, whether to transform glycerol into other chemical products of interest or even use it in the production of catalysts. Among the several studies found in the literature, the use of low-cost materials and/or wastes from the most diverse activities to prepare active catalytic materials for the transformation of Gly has been increasingly reported due to its valuable advantages, especially related to the cost of raw materials and environmental aspects. Thus, this brief review article presents the relationship between catalysis, low-cost materials, waste, and glycerol, through different studies that show glycerol being transformed through reactions catalyzed by materials produced from low-cost sources/waste or with the glycerol itself used as a catalyst.