Platinum (II) and palladium (II) complexes: synthesis, antimicrobial and antifungal activity

The study aims to synthesize and examine the biological activity of mono- and binuclear platinum (II) and palladium (II) complexes containing terminal and bridging nitrite ligands against the test cultures of Bacillus subtilis B4647, Aspergillus brasiliensis (niger) F679, Pseudomonas aeruginosa B8243, and Escherichia coli. Through the interaction of mononuclear platinum (II) and palladium (II) complexes, dimeric complexes having nitrite ligands were synthesized. The composition and structure of these complexes were established using elemental analysis, conductometry, potentiometry, cryoscopy, infrared spectroscopy, X-ray diffraction analysis, and X-ray fluorescence analysis. A way to coordinate nitrite ligands with the central atom was established. Antimicrobial and antifungal properties were evaluated according to the capability of the synthesized complexes to inhibit the activity of bacteria and fungi via diffusion in agar and in vitro dilution. The minimum inhibitory and bactericidal concentrations of the complexes suppressing the visible growth of microorganisms and fungi, as well as exhibiting their bactericidal effect, ranged from 62.5–125 μmol/dm3. The obtained results revealed a high activity of the palladium (II) binuclear complex of the non-electrolytic type and the platinum (II) binuclear complex of the cationic type. Unlike mononuclear complexes, palladium and platinum binuclear complexes demonstrate higher antibacterial activity. Antibacterial effectiveness exhibited by the palladium complex of the non-electrolytic type against bacteria Bacillus subtilis and Escherichia coli, as well as fungi Aspergillus niger, is more pronounced. The only exception is the antimicrobial activity of the palladium complex against Pseudomonas aeruginosa, which is comparable to that of the binuclear platinum complex of the cationic type. By changing the structure of the complex, the composition and charge of the inner sphere, the number of coordination centers, as well as the nature and denticity of ligands, it is possible to achieve a higher toxic effect of the complexes against bacteria and fungi.

Near-Infrared Vapochromism in Lipid-Packaged Mixed-Valence Coordination Polymers

Reversible vapochromism in the NIR region is achieved for a mixed-valence platinum complex with lipid counterions, from which exclusion of crystallization water by organic vapor alters lipid molecular orientation that...

Synthesis and Characterization of New Guanine Complexes of Pt(IV) and Pd(II) by X-Ray Diffraction and Hirshfeld Surface Analysis

The aim of the work was to synthesize new perspective compounds of palladium and platinum with nitrogenous bases (guanine), promising for use in biomedicine and catalysis. The article describes the synthesis of new [PdCl2(HGua)2]Cl2·H2O and [PtCl5(HGua)]·2H2O compounds using wet chemistry methods. The structure of the obtained single crystals was established by the method of single crystal X-ray diffraction. The complexes have an M-N bond, and the organic ligand is included in the first coordination sphere. The analysis of Hirshfeld surfaces for the obtained complexes and their analogues for the analysis of intermolecular interactions was carried out. In the palladium complex we obtained, π-halogen and π-stacking interactions were found; in analogues, such interactions were not found. π-halogen and halogen interactions were found in structure of platinum complex and its analogues.

Multifunctional Polyoxometalate-Platforms for Supramolecular Light-driven Hydrogen Evolution

Multifunctional supramolecular systems are a central research topic in light-driven solar energy conversion. Here, we report a polyoxometalate (POM)-based supramolecular dyad, where two platinum-complex hydrogen evolution catalysts are covalently anchored to an Anderson polyoxomolybdate anion. Supramolecular electrostatic coupling of the system to an iridium photosensitizer enables visible light-driven hydrogen evolution. Combined theory and experiment demon-strate the multifunctionality of the POM, which acts as photosensitizer / catalyst-binding-site and facilitates light-induced charge-transfer and catalytic turnover. Chemical modification of the Pt-catalyst site leads to increased hydrogen evolution reactivity. Mechanistic studies shed light on the role of the individual components and provide a molecular understanding of the interactions which govern stability and reactivity. The system could serve as a blueprint for multifunctional polyoxometalates in energy conversion and storage.

Domino Suzuki-Miyaura Cross-Coupling and Oxidative Condensation Reaction: An Approach Towards Synthesis of Phenanthridine and Its Analogues

Phenanthridines belong to a very important class of nitrogen containing heterocylic compounds and constitute core structure of many natural alkaloids such as trisphaeridine and nitidine. Quarternarybenzo[c]phenanthridine alkaloids (QBA) represented by sanguinarine(SA), chelerythrine (CHE), and fagaronine (FA) exhibit antifungal and nematocidal properties and also serve as the core structure of broad range of medicinally active molecules showing anti-tumor activity, anti-viral property, anti-neoplastic or mutagenic activity through DNA-intercalation. Phenanthridines are also utilized for the synthesis of compounds of therapeutic interests such as anticancer platinum complex typified by phenanthriplatin antibacterial, anti-infectives, antprotozoal, antituberculosis, antitrypanosomiasis compounds. Although conventional synthetic methods towards their development showed their own advantages, they generally involved either multistep processes with low yield, or starting materials which are not readily available or requirement of prefunctionalization. Hence herein we present the development of an efficient and convenient synthetic methodology towards these versatile compounds. <br>

Domino Suzuki-Miyaura Cross-Coupling and Oxidative Condensation Reaction: An Approach Towards Synthesis of Phenanthridine and Its Analogues

Phenanthridines belong to a very important class of nitrogen containing heterocylic compounds and constitute core structure of many natural alkaloids such as trisphaeridine and nitidine. Quarternarybenzo[c]phenanthridine alkaloids (QBA) represented by sanguinarine(SA), chelerythrine (CHE), and fagaronine (FA) exhibit antifungal and nematocidal properties and also serve as the core structure of broad range of medicinally active molecules showing anti-tumor activity, anti-viral property, anti-neoplastic or mutagenic activity through DNA-intercalation. Phenanthridines are also utilized for the synthesis of compounds of therapeutic interests such as anticancer platinum complex typified by phenanthriplatin antibacterial, anti-infectives, antprotozoal, antituberculosis, antitrypanosomiasis compounds. Although conventional synthetic methods towards their development showed their own advantages, they generally involved either multistep processes with low yield, or starting materials which are not readily available or requirement of prefunctionalization. Hence herein we present the development of an efficient and convenient synthetic methodology towards these versatile compounds. <br>

On the Rate of Interaction of Sodium Borohydride with Platinum (IV) Chloride Complexes in Alkaline Media

In this work, sodium borohydride was used as a strong reductant of traces of platinum complex ions. The investigations of the kinetics of redox reaction between platinum(IV) chloride complex ions and sodium borohydride were carried out. For the first time, the kinetic experiments were carried out in a basic medium (pH~13), which prevents NaBH4 from decomposition and suppresses the release of hydrogen to the environment. The rate constants of Pt(IV) reduction to Pt(II) ions under different temperatures and concentrations of chloride ions conditions were determined. In alkaline solution (pH~13), the values of enthalpy and entropy of activation are 29.6 kJ/mol and –131 J/mol K. It was also found that oxygen dissolved in the solution strongly affects kinetics of the reduction process. Using collected results, the reduction mechanism was suggested. For the first time, the appearance of diborane as an intermediate product during Pt(IV) ions reduction was suggested. Moreover, the influence of oxygen present in the reacting solution on the rate of reduction reaction was also shown.