Ultrasound assisted synthesis, characterization and electrochemical study of a tetradentate oxovanadium diazomethine complex

Pincer Complexes Derived from Tridentate Schiff Bases for Their Use as Antimicrobial Metallopharmaceuticals

Within the current challenges in medicinal chemistry, the development of new and better therapeutic agents effective against infectious diseases produced by bacteria, fungi, viruses, and parasites stands out. With chemotherapy as one of the main strategies against these diseases focusing on the administration of organic and inorganic drugs, the latter is generally based on the synergistic effect produced by the formation of metal complexes with biologically active organic compounds. In this sense, Schiff bases (SBs) represent and ideal ligand scaffold since they have demonstrated a broad spectrum of antitumor, antiviral, antimicrobial, and anti-inflammatory activities, among others. In addition, SBs are synthesized in an easy manner from one-step condensation reactions, being thus suitable for facile structural modifications, having the imine group as a coordination point found in most of their metal complexes, and promoting chelation when other donor atoms are three, four, or five bonds apart. However, despite the wide variety of metal complexes found in the literature using this type of ligands, only a handful of them include on their structures tridentate SBs ligands and their biological evaluation has been explored. Hence, this review summarizes the most important antimicrobial activity results reported this far for pincer-type complexes (main group and d-block) derived from SBs tridentate ligands.

Alternative Technologies That Facilitate Access to Discrete Metal Complexes

Organometallic complexes: these two words jump to the mind of the chemist and are directly associated with their utility in catalysis or as a pharmaceutical. Nevertheless, to be able to use them, it is necessary to synthesize them, and it is not always a small matter. Typically, synthesis is via solution chemistry, using a round-bottom flask and a magnetic or mechanical stirrer. This review takes stock of alternative technologies currently available in laboratories that facilitate the synthesis of such complexes. We highlight five such technologies: mechanochemistry, also known as solvent-free chemistry, uses a mortar and pestle or a ball mill; microwave activation can drastically reduce reaction times; ultrasonic activation promotes chemical reactions because of cavitation phenomena; photochemistry, which uses light radiation to initiate reactions; and continuous flow chemistry, which is increasingly used to simplify scale-up. While facilitating the synthesis of organometallic compounds, these enabling technologies also allow access to compounds that cannot be obtained in any other way. This shows how the paradigm is changing and evolving toward new technologies, without necessarily abandoning the round-bottom flask. A bright future is ahead of the organometallic chemist, thanks to these novel technologies.

1,1′-{(1E,1′E)-[Octane-1,8-diylbis(azanylylidene)]bis(methanylylidene)}bis(naphthalen-2-ol) in the zwitterionic form

The title compound, C30H32O2N2, is formed from two units ofortho-hydroxynaphthaldehyde bridged with 1,8-diaminooctane. In the solid state, it exists as a double zwitterion. The N atoms are protonated and the C—O−bonds lengths are 1.265 (2) Å, with intramolecular N—H...O hydrogen bonds formingS(6) ring motifs. The molecule has twofold rotational symmetry, with the twofold axis bisecting the central –CH2—CH2– bond of the bridging octane chain. In the crystal, molecules are linked by N—H...O hydrogen bonds, forming chains propagating along the [-201] direction. The chains are linkedviaC—H...O hydrogen bonds, forming a supramolecular three-dimensional framework structure.

2,2′-[(1E,1′E)-1,2-Phenylenebis(azanylylidene)bis(methanylylidene)]bis(4-bromophenol)

In the title compound, C20H14Br2N2O2, there are two intramolecular O—H...N hydrogen bonds formingS(6) ring motifs. The outer benzene rings are inclined to the central benzene ring by 39.09 (11) and 24.31 (11)°, and to one another by 37.12 (11)°. In the crystal, molecules are linked by a short Br...O contact [3.1307 (19) Å], forming zigzag chains propagating along thea-axis direction. The chains are linked by weak offset π–π interactions [intercentroid distance = 3.716 (1) Å], forming layers parallel to theacplane.