New complexes of manganese (II), nickel (II) and copper (II) with derived benzoxazole ligands: Synthesis, characterization, DFT, antimicrobial activity, acute and subacute toxicity

A Halomanganates(II) with P,P'-Diprotonated Bis(2-Diphenylphosphinophenyl)ether: Wavelength-Excitation Dependence of the Quantum Yield and Role of the Non-Covalent Interactions

A [H2DPEphos][MnX4] [X = Br, Cl] tetrahalomanganates(II) with P,P'-diprotonated bis[2-(diphenylphosphino)phenyl]ether cation has been designed and investigated in photophysics and EPR terms. The complexes exhibit a green luminescence resulted from the Mn(II) d-d transitions (4T1→6A1) with the wavelength-excitation dependence of the quantum yield. The solid [H2DPEphos][MnBr4] complex exhibits a bright green phosphorescence (λmax = 515 nm) with the high luminescence quantum yield depending on the excitation energy whereas the solid [H2DPEphos][MnCl4] complex exhibits a very weak phosphorescence (λmax = 523 nm). The unexpected shorter luminescence lifetime for the [H2DPEphos][MnCl4] than for the [H2DPEphos][MnBr4] at 300 K can be a result of the higher non-radiative relaxation contribution. On the one hand, the non-covalent PH…X(Mn) interactions quench the manganese(II) luminescence. On the other hand, the PH…X(Mn) interactions are a pathway of the excitation transfer from [H2DPEphos]2+ to [MnX4]2-.

Metal Complexes as Promising Agents for Biomedical Applications

Background::

In this review article, a brief overview of novel metallotherapeutic agents (with an emphasis on the complexes of essential biometals) promising for medical application is presented. We have also focused on the recent work carried out by our research team, specifically the development of redox-active antimicrobial complexes of sterically hindered diphenols with some essential biometals (copper, zinc, nickel).

Results::

The complexes of essential metals (manganese, iron, cobalt, nickel, copper, zinc) described in the review show diverse in vitro biological activities, ranging from antimicrobial and antiinflammatory to antiproliferative and enzyme inhibitory. It is necessary to emphasize that the type of organic ligands in these metal complexes seems to be responsible for their pharmacological activities. In the last decades, there has been a significant interest in synthesis and biological evaluation of metal complexes with redox-active ligands. A substantial step in the development of these redox-active agents is the study of their physicochemical and biological properties, including investigations in vitro of model enzyme systems, which can provide evidence on a plausible mechanism underlying the pharmacological activity. When considering the peculiarities of the pharmacological activity of the sterically hindered diphenol derivatives and their nickel(II), copper(II) and zinc(II) complexes synthesized, we took into account the following: (i) all these compounds are potential antioxidants and (ii) their antimicrobial activity possibly results from their ability to affect the electron-transport chain.

Conclusion::

We obtained novel data demonstrating that the level of antibacterial and antifungal activity in the series of the above-mentioned metal-based antimicrobials depends not only on the nature of the phenolic ligands and complexing metal ions, but also on the lipophilicity and reducing ability of the ligands and metal complexes, specifically regarding the potential biotargets of their antimicrobial action – ferricytochrome c and the superoxide anion radical. The combination of antibacterial, antifungal and antioxidant activity allows one to consider these compounds as promising substances for developing therapeutic agents with a broad spectrum of activities.

Efficient procedure with new fused pyrimidinone derivatives, Schiff base ligand and its La and Gd complexes by green chemistry

Synthetic strategies were developed for the construction of some newer more potent derivatives of thiobarbituric acid and its Schiff base metal complexes in both bulk and at the nanoscale.

Techniques in the synthesis of mononuclear manganese complexes: a review

This article describes an overview of the synthetic techniques and protocols for the preparation of new ligands and respective manganese (Mn) complexes to be tested for biomedical applications. Mn is an essential and biocompatible element, the complexes of which have diverse medicinal applications. The most significant use of Mn complexes is their application against reactive oxygen species in biological systems, and due to this, three Mn-incorporated complexes (AEOL-10150, EUK-134, and M40403) are already under clinical trials. Hence, the interest in synthesizing biologically active Mn complexes is rapidly increasing. Mn complexes are commonly synthesized using either water or ethanol as a reaction medium for their possible usage in biological systems. Using common Mn salts along with suitable organic ligand works well in the presence of little heat to obtain Mn complexes of interest.