Synthesis, structural features, antibacterial behaviour and theoretical investigation of two new manganese(III) Schiff base complexes

Evaluation of metal-based antimicrobial compounds for the treatment of bacterial pathogens

Antimicrobial resistance (AMR) is one of the greatest global health challenges of modern times and its prevalence is rising worldwide. AMR within bacteria reduces the efficacy of antibiotics and increases both the morbidity and the mortality associated with bacterial infections. Despite this growing risk, few antibiotics with a novel mode of action are being produced, leading to a lack of antibiotics that can effectively treat bacterial infections with AMR. Metals have a history of antibacterial use but upon the discovery of antibiotics, often became overlooked as antibacterial agents. Meanwhile, metal-based complexes have been used as treatments for other diseases, such as the gold-containing drug auranofin, used to treat rheumatoid arthritis. Metal-based antibacterial compounds have novel modes of action that provide an advantage for the treatment of bacterial infections with resistance to conventional antibiotics. In this review, the antibacterial activity, mode of action, and potential for systemic use of a number of metal-based antibacterial complexes are discussed. The current limitations of these compounds are highlighted to determine if metal-based agents are a potential solution for the treatment of bacterial infections, especially those resistant to conventional antibiotics.

Intermolecular interaction energies and magnetic properties of spin-isolated multinuclear CuII complexes

Dinuclear Cu^II complexes with 3,5-dinitrobenzoates and 2,2'-bipyridine (2) or 1,10-phenanthroline (3) were synthesized and characterized. A complete energy framework analysis using the HF/3-21G energy model was performed which found that dispersion forces and C-H...O interactions are responsible for the crystal structure features. The magnetic properties of the complexes show a weak magnetic exchange between spins, resulting in low exchange constants of -2.72 (1) cm^-1 and -1.10 (1) cm^-1 for complexes (2) and (3), respectively. This results from the low overlap between magnetic orbitals induced by 3,5-dinitrobenzoate bridges and the arrangement of the magnetic orbitals. Consequently, the dinuclear complexes (2) and (3) behave as spin-isolated multinuclear Cu^II species in contrast to the trinuclear complex with similar ligands.

Effects of metal-organic complex Ni(Salen) on thermal decomposition of 1,1-diamino-2,2-dinitroethylene (FOX-7)

The development of novel combustion catalysts is critical for improving combustion performance of high-energy solid propellants. In this work, a nickel-based Schiff base complex, N,N′-bis(salicylidene)ethylenediamino nickel [Ni(Salen)], as a candidate for the combustion catalyst of solid propellants, was synthesized with high purity. The effects of Ni(Salen) on the thermal decomposition reaction of FOX-7, which is closely related to its combustion properties in propellants, were systematically investigated and the corresponding mechanisms were also evaluated through comparison and analysis. Under the action of Ni(Salen), peak temperatures of the two decomposition processes of FOX-7 were reduced from 235.7 and 296.3 °C to 233.7 and 268.7 °C, respectively. The investigations into the mechanisms revealed the interactions between the Schiff base skeleton in Ni(Salen) and FOX-7, which promotes the decomposition of the remaining FOX-7. In addition, it was found that NiO, which was a decomposition product of Ni(Salen), also played an important role in promoting the thermal decomposition of FOX-7.

The development of novel combustion catalysts is critical for improving combustion performance of high-energy solid propellants.