ESCA-Untersuchungen an Schwermetallchelaten substituierter N-Acyl-thio- und -selenoharnstoffe

Acylselenoureas, selenosemicarbazones and selenocarbamate esters: Versatile ligands in coordination chemistry

Acylselenoureas, selenosemicarbazones and selenocarbamate esters from complexes with various transition- and main-group-metals, adopting several coordination modes.

Accelerated Anti-Markovnikov Alkene Hydrosilylation with Humic-Acid-Supported Electron-Deficient Platinum Single Atoms

The hydrosilylation reaction is one of the largest-scale applications of homogeneous catalysis, and Pt homogeneous catalysts have been widely used in this reaction for the commercial manufacture of silicon products. However, homogeneous Pt catalysts result in considerable problems, such as undesired side reactions, unacceptable catalyst residues and disposable platinum consumption. Here, we synthesized electron-deficient Pt single atoms supported on humic matter (Pt₁ @AHA_U_400), and the catalyst was used in hydrosilylation reactions, which showed super activity (turnover frequency as high as 3.0×10⁷  h^-1 ) and selectivity (>99 %). Density functional theory calculations reveal that the high performance of the catalyst results from the atomic dispersion of Pt and the electron deficiency of the Pt₁ atoms, which is different from conventional Pt nanoscale catalysts. Excellent performance is maintained during recycle experiments, indicating the high stability of the catalyst.

Post-Synthetic Modification of ZIF-8 Crystals and Films through UV Light Photoirradiation: Impact on the Physicochemical Behavior of the MOF

The physicochemical modification of Metal-Organic Frameworks (MOFs) is a current challenge in the search to improve their performance in different technological applications. In this work we analyze the post-synthetic modification of ZIF-8 crystals and films through a simple and clean treatment that involves the exposure to a UV lamp under environmental conditions. It is demonstrated that a short treatment alters the MOF structure and chemistry, providing a modified ZIF-8 due to partial disconnections of its structure which increase the amount of terminal surface species such as Zn-OH and -C=N-H, but without compromising the overall MOF structure, specific surface area or thermal stability. Additionally, it leads to changes in several properties of the ZIF-8, such as its capacity to accumulate charge through pseudocapacitive processes, its interaction with nitric oxide and its light absorption behavior. This strategy of modifying ZIF-8 without the use of chemicals through a gentle disconnection of its own structure could open new perspectives of post-functionalization of crystals and films of ZIF-8 to be used in a wide range of applications.

Hollow, spherical nitrogen-rich porous carbon shells obtained from a porous organic framework for the supercapacitor

Hollow, spherical nitrogen-rich porous carbon shells were prepared as supercapacitor electrode materials through the carbonization of structure-controlled porous organic frameworks at high temperature. The structure and electrochemical properties of the resulting carbonized materials were systematically characterized. Experimental results revealed that the nitrogen-rich hollow carbon spheres obtained at 800 °C were a kind of amorphous carbon with micropores on the shell frame and with specific surface areas as high as 525 m2 g(-1). The prepared porous carbon possessed a specific capacitance of 230 F g(-1) at a current density of 0.5 A g(-1) and could retain ∼98% of the initial capacitance after 1500 successive charge-discharge cycles. Electrochemical impedance spectroscopy indicated that the material has a small equivalent series resistance (0.62 Ω). All of these values demonstrated that the prepared porous carbon is a promising supercapacitor material. The proposed method represents a simple approach towards the preparation of unique structures of nitrogen-containing porous carbon that exhibit the advantages of having a simple preparation process, a wide availability of precursors, flexible control of the structure, and an easier adjustment of the amount of heteroatoms.

Synthesis, characterization, and in vitro cytotoxic activities of benzaldehyde thiosemicarbazone derivatives and their palladium (II) and platinum (II) complexes against various human tumor cell lines

The palladium (II) bis-chelate Pd (L¹⁻³)₂ and platinum (II) tetranuclear Pt₄(L⁴)₄ complexes of benzaldehyde thiosemicarbazone derivatives have been synthesized, and characterized by elemental analysis and IR, FAB(+)-mass and NMR (¹H, ¹³C) spectroscopy. The complex Pd(L²)₂ [HL² = m-CN-benzaldehyde thiosemicarbazone] shows a square-planar geometry with two deprotonated ligands (L) coordinated to Pd^II through the nitrogen and sulphur atoms in a transarrangement, while the complex Pt₄(L⁴)₄ [HL⁴ = 4-phenyl-1-benzaldehyde thiosemicarbazone] has a tetranuclear geometry with four tridentate ligands coordinated to four Pt^II ions through the carbon (aromatic ring), nitrogen, and sulphur atoms where the ligands are deprotonated at the NH group. The in vitro antitumor activity of the ligands and their complexes was determined against different human tumor cell lines, which revealed that the palladium (II) and platinum (II) complexes are more cytotoxic than their ligands with IC₅₀ values at the range of 0.07–3.67 μM. The tetranuclear complex Pt₄(L⁴)₄, with the phenyl group in the terminal amine of the ligand, showed higher antiproliferative activity (CI₅₀ = 0.07–0.12 μM) than the other tested palladium (II) complexes.

Pd(II)- and Pt(II)-cimetidine complexes. Crystal structure of trans-[Pt(N,S-cimetidine)(2)]Cl(2)(*)12H(2)O

The influence of cimetidine on patients under cisplatin treatment for cancer is controversial. It has moderate or no effects on several types of cancer and its effects on the nephrotoxicity induced by cisplatin are uncertain. To examine the binding properties and antiproliferative effects of the known anticancer noble metals, cimetidine (cim) was complexed to platinum(II) and palladium(II). The crystal structure of the Pt-cim compound shows two molecules of cimetidine coordinated to the metal through thioether sulfur and imidazolic nitrogen whereas spectroscopic studies in solution for Pd-cim reveal that the ratio of the metal to cimetidine is 1:1 with identical coordination environments. To determine the antitumor activity of the drugs, the interaction of the metallic complexes and free cimetidine with DNA was assessed. Their cytotoxic activity was compared with that of cisplatin.

Palladium and platinum famotidine complexes

The molecule of the well-known ulceration inhibitor, famotidine, is an excellent coordinator of transition metal ions. The guanidine, amine group and thiazole nitrogen, and the thioether sulphur are preferential sites to bind metal ions. Pd(II) and Pt(II) derivatives of famotidine have been synthesized and studied structurally. There is evidence that the palladium complex is a monomer while the platinum complex forms a dimer. Due to the interesting structure of the platinum complex several assays have examined the possible antitumour activity. Changes in DNA conformation induced by both complexes have been detected by CD, interstrand crosslinking interactions and electrophoretic mobility, but studies of the cytotoxicity of the platinum compound with U937 human leukemia cells and HeLA human womb carcinoma cells show only a small antiproliferative potential.