Synthesis, characterization and catalytic properties of heterogeneous iron(III) tetradentate Schiff base complexes for the aerobic epoxidation of styrene

A Nonheme Iron(III) Superoxide Complex Leads to Sulfur Oxygenation

A new alkylthiolate-ligated nonheme iron complex, FeII(BNPAMe2S)Br (1), is reported. Reaction of 1 with O2 at -40 °C, or reaction of the ferric form with O2•- at -80 °C, gives a rare iron(III)-superoxide intermediate, [FeIII(O2)(BNPAMe2S)]+ (2), characterized by UV-vis, 57Fe Mössbauer, ATR-FTIR, EPR, and CSIMS. Metastable 2 then converts to an S-oxygenated FeII(sulfinate) product via a sequential O atom transfer mechanism involving an iron-sulfenate intermediate. These results provide evidence for the feasibility of proposed intermediates in thiol dioxygenases.

Insight into the Anticancer Activity of Copper(II) 5-Methylenetrimethylammonium-Thiosemicarbazonates and Their Interaction with Organic Cation Transporters

A series of four water-soluble salicylaldehyde thiosemicarbazones with a positively charged trimethylammonium moiety ([H2LR]Cl, R = H, Me, Et, Ph) and four copper(II) complexes [Cu(HLR)Cl]Cl (1-4) were synthesised with the aim to study (i) their antiproliferative activity in cancer cells and, (ii) for the first time for thiosemicarbazones, the interaction with membrane transport proteins, specifically organic cation transporters OCT1-3. The compounds were comprehensively characterised by analytical, spectroscopic and X-ray diffraction methods. The highest cytotoxic effect was observed in the neuroblastoma cell line SH-5YSY after 24 h exposure and follows the rank order: 3 > 2 > 4 > cisplatin > 1 >>[H2LR]Cl. The copper(II) complexes showed marked interaction with OCT1-3, comparable to that of well-known OCT inhibitors (decynium 22, prazosin and corticosterone) in the cell-based radiotracer uptake assays. The work paves the way for the development of more potent and selective anticancer drugs and/or OCT inhibitors.

A heterogenized chiral imino indanol complex of manganese as an efficient catalyst for aerobic epoxidation of olefins

A new composite was synthesized by grafting the (1R,2S)-1-(N-salicylideneamino)-2-indanol complex of Mn onto graphene oxide/Fe₃O₄@C. It catalysed the aerobic epoxidation of olefins with a selectivity of >98% and enantioselectivity of >99%.

Encapsulation of chiral Fe(salen) in mesoporous silica structures for use as catalysts to produce optically active sulfoxides

Solid catalysts which are heterogeneous at the macroscopic scale but homogeneous at the microscopic level were prepared by the encapsulation of Fe(salen) by a “ship in a bottle” approach.

Synthesis, characterization and experimental, theoretical, electrochemical, antioxidant and antibacterial study of a new Schiff base and its complexes

A new Schiff base ligand was synthesized by reaction of salicylaldehyde with 1,6-bis(4-chloro-2-aminophenoxy)hexane. Then the Schiff base complexes were synthesized by metal salts and the Schiff base. The metal to ligand ratio of metal complexes was found to be 1:1. The Cu(II) complex is proposed to be square planar and the Co(II), Ni(II), Mn(II) and Zn(II) complexes are proposed to be tetrahedral geometry. The Ti(III) and V(III) complexes are proposed to be a capped octahedron in which a seventh ligand has been added to triangular face. The complexes are non-electrolytes as shown by their molar conductivities (ΛM). The structure of metal complexes is proposed from elemental analysis, FT-IR, UV-vis, magnetic susceptibility measurements, molar conductivity measurements, Mass Spectra and thermal gravimetric analysis. In addition antimicrobial and antioxidant studies, cyclic voltammetry of the complexes, theoretical 1H NMR and HOMO-LUMO energy calculations of the new di-functional ligand were done.

Toward new classes of potent antibiotics: synthesis and antimicrobial activity of novel metallosaldach-imidazolium salts

Imidazolium salts (Im(+)-R(2)R(3)-Cl(-)) attached to the N,N'-bis(salicylidene)-(±)-trans-1,2-diaminocyclohexane (saldach) backbone (4a-f) have been designed and successfully applied for the synthesis of the corresponding mononuclear complexes with Mn(III) and Fe(III) ions. The molecular structures of the saldach ligands H2(R(1))2saldach(Im(+)-R(2)R(3)-Cl(-))2 (R(1) = H, tert-Bu, R(2) = H, Et, n-Bu, R(3) = H, Me) and their [M(III)Cl{(R(1))2saldach(Im(+)-R(2)R(3)-Cl(-))2}] (M = Mn, Fe) complexes have been established. The free ligands exist as the phenol-OH and not as the zwitterionic (imine)N-H(+)· · ·(-)O(phenol) tautomer. Antimicrobial activity of the target compounds revealed higher potent antibacterial activity against Salmonella aureus, B. subtilis while less effective against E. coli and C. albicans and inactivity against A. flavus. Compound (4d) and its Fe(III) complex (6d) exhibit remarkable extra-potent bactericidal activity.

Use of polymer-bound Schiff base as a new liquid binding agent of diffusive gradients in thin-films for the measurement of labile Cu²⁺, Cd²⁺ and Pb²⁺

A new diffusive gradients in thin-films (DGT) device with solution of polymer-bound Schiff base (Py-PEI) derived from poly(ethyleneimine) and 2-pyridinecarboxaldehyde as the binding agent (Py-PEI DGT) was developed for measuring labile Cu(2+), Cd(2+) and Pb(2+) in waters. In synthetic solution, uptake percentages of Cu(2+), Cd(2+) and Pb(2+) by Py-PEI DGT were 99.2 ± 4.4%, 103.7 ± 4.8% and 98.7 ± 5.5% of the total metals, respectively. Performance of Py-PEI DGT was independent of pH 4-8.5 and ionic strength 1 × 10(-4)-0.1 mol L(-1). The uptake of labile metals showed agreement with the theoretical values of free ions in EDTA solution, and decreased with increase of humic acid (HA) and dissolved organic carbon (DOC) contents in water due to the complexation of HA and DOC with metals. DGT devices containing different liquid binding agents (Py-PEI, polyacrylate (PA) and poly(4-styrenesulfonate) (PSS)) were deployed in the same solution. The higher uptake percentages of Py-PEI DGT (13.2 ± 1.1, 26.5 ± 2.4 and 62.7 ± 3.2% of total Cu(2+), Cd(2+) and Pb(2+)) were obtained with respective to PSS DGT (6.7 ± 0.6, 9.2 ± 0.9 and 29.6 ± 2.7% of total above metals) and PA DGT (8.9 ± 0.9 and 16.2 ± 1.1% of total Cu(2+) and Cd(2+)) due to its relatively strong binding affinity with metals.