Synthesis and characterization of Cu(II) paddlewheel complexes possessing fluorinated carboxylate ligands

Synthesis, characterization, antioxidant, antileishmanial, anticancer, DNA and theoretical SARS-CoV-2 interaction studies of copper(II) carboxylate complexes

Copper(II) carboxylate complexes [Cu₂(OOCR)₄L₂] (1) and [Cu₂(OOCR`)<sub>4</sub>OCO(R`)CuL₂]_n (2), where L = 2-methyl pyridine, R = 2-chlorophenyl acetate and R` = 2-fluorophenyl acetate were synthesized and characterized by FT-IR spectroscopy and single crystal X-ray analysis. Complex 1 exhibits the typical paddlewheel array of a dinuclear copper(II) complex with carboxylate ligands. In complex 2, this scaffold is further extended into a polymeric arrangement based on alternate paddlewheel and square planar moieties with distinct coordination spheres. The complexes showed better 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging activities and have been found to be more potent antileishmanial agents than their corresponding free ligand acid species. UV-Vis absorption titrations revealed good DNA binding abilities {Kb = 9.8 × 10⁴ M^-1 (1) and 9.9 × 10⁴ M^-1 (2)} implying partial intercalation of the complexes into DNA base pairs along with groove binding. The complexes displayed in vitro cytotoxic activity against malignant glioma U-87 (MG U87) cell lines. Computational docking studies further support complex-DNA binding by intercalation. Molecular docking investigations revealed probable interactions of the complexes with spike protein, the nucleocapsid protein of SARS-CoV-2 and with the angiotensin converting enzyme of human cells.

Structure of tetra-kis-(μ-deca-noato-κ2 O:O')bis-[(4-methyl-pyridine-κN)copper(II)], a dimeric copper(II) complex

The 4-methyl-pyridine (4-Mepy) based dimeric copper(II) carboxyl-ate complex [Cu2(C10H19O2)4(C6H7N)2] or [Cu2(μ-O2CC9H19)4(4-Mepy)2] crystallizes with triclinic (P ) symmetry. The two CuII ions exhibit a distorted square-pyramidal environment and are connected into a centrosymmetric paddle-wheel dinuclear cluster [Cu⋯Cu = 2.6472 (8) Å] via four bridging carboxyl-ate ligands arranged in the syn-syn coordination mode. The apical positions around the paddle-wheel copper centers are occupied by the N atoms of the 4-methyl-pyridine ligands. The structure exhibits disorder of the terminal alkyl carbon atoms in the deca-noate chains.

Dissolution of metal oxides in task-specific ionic liquid

Due to their typically low reactivity, the activation of metal oxides, as found in ores, earths and minerals, is in general performed by high temperature reactions, which consume much energy. Owing to the prevalence of fossil fuels, this is accompagnied by the generation of large amounts of CO₂. Alternatively, ionic liquids (ILs) can be used as solvents for metal oxide dissolution and downstream chemistry at much lower temperatures. The dissolution ability of the dry ionic liquid betainium bis(trifluoromethylsulfonyl)imide, [Hbet][NTf₂], was investigated for 30 metal oxides at 175 °C and compared to chloride containing IL [Hbet]₂[NTf₂]Cl. A general dissolution-promoting effect of chloride anions was found, regarding reaction time as well as the variety of dissolved metal oxides. Up to now, the dissolution in [Hbet]₂[NTf₂]Cl is limited to basic or amphoteric metal oxides and assumed to be influenced by multiple factors, such as reaction conditions and the lattice energy of the metal oxide as well as its crystal structure. Comprehensive investigations were performed for the dissolution of CuO, which led to the discovery of the water-free complex compound [Cu₂(bet)₄(NTf₂)₂][NTf₂]₂. Proceeding from this compound, a complete exchange of the O-coordination sphere by other ligands was demonstrated, opening up promising possibilities for downstream chemistry.

Investigation on the dissolution of 30 metal oxides in the water-free ionic liquid [Hbet][NTf₂] and the catalytic effect of chloride for the application in green ore processing.

Enantioselective synthesis of α-oxy amides via Umpolung amide synthesis

α-Oxy amides are prepared through enantioselective synthesis using a sequence beginning with a Henry addition of bromonitromethane to aldehydes and finishing with Umpolung Amide Synthesis (UmAS). Key to high enantioselection is the finding that ortho-iodo benzoic acid salts of the chiral copper(II) bis(oxazoline) catalyst deliver both diastereomers of the Henry adduct with high enantiomeric excess, homochiral at the oxygen-bearing carbon. Overall, this approach to α-oxy amides provides an innovative complement to alternatives that focus almost entirely on the enantioselective synthesis of α-oxy carboxylic acids.

Aqua-(3-fluoro-benzoato-κO)(3-fluoro-benzoato-κO,O')(1,10-phenanthroline-κN,N')cobalt(II)

In the title compound, [Co(C₇H₄FO₂)₂(C₁₂H₈N₂)(H₂O)], the Co^II ion is coordinated by two O atoms from one 3-fluoro­benzoate (fb) ligand and one O atom from another fb ligand, two N atoms from the 1,10-phenanthroline ligand and a water mol­ecule in a distorted octa­hedral geometry. An intra­molecular O—H⋯O hydrogen bond occurs. Inter­molecular O—H⋯O hydrogen bonds link pairs of mol­ecules into centrosymmetric dimers. Weak inter­molecular C—H⋯O and C—H⋯F hydrogen bonds and π–π inter­actions between the aromatic rings [shortest centroid–centroid distance = 3.4962 (2) Å] further stabilize the crystal packing.

Synthesis and characterization of tin(II) complexes of fluorinated Schiff bases derived from amino acids

New tin(II) complexes of general formula Sn(L)(2) (L=monoanion of 3-methyl-4-fluoro-acetophenone phenylalanine L(1)H, 3-methyl-4-fluoro-acetophenone alanine L(2)H, 3-methyl-4-fluoro acetophenone tryptophan L(3)H, 3-methyl-4-fluoro-acetophenone valine L(4)H, 3-methyl-4-fluoro-acetophenone isoleucine L(5)H and 3-methyl-4-fluoro-acetophenone glycine L(6)H) have been prepared. It is characterized by elemental analyses, molar conductance measurements and molecular weight determinations. Bonding of these complexes is discussed in terms of their UV-visible, infrared, and nuclear magnetic resonance ((1)H, (13)C, (19)F and (119)Sn NMR) spectral studies. The ligands act as bidentate towards metal ions, via the azomethine nitrogen and deprotonated oxygen of the respective amino acid. Elemental analyses and NMR spectral data of the ligands with their tin(II) complexes agree with their proposed square pyramidal structures. A few representative ligands and their tin complexes have been screened for their antibacterial activities and found to be quite active in this respect.