Dinuclear Schiff Base Complexes Research Articles

A pyrazolone-based dinuclear Cu(II) Schiff-base complex: DFT studies on the rate-determining steps of the tautomerism in the ligand and molecular docking modelling with COVID-19 main protease (6LU7)

A new dinuclear Schiff-base complex, [Cu2L'2(μ-OAc)2], was synthesized and characterized by various spectroscopic methods and single-crystal X-ray diffraction (SCXRD). The symmetrical H2L ligand was synthesized from the reaction between 4-acetyl-3-methyl-1-phenyl-2-pyrazoline-5-one (or acylpyrazolone) with 1,3-propanediamine, but upon reaction with a metal salt, it gave the unsymmetrical HL'. The transition states and rates of interconversion between different tautomeric forms of HL' were studied by DFT computations. The imine-one (Z) in the gas phase and imine-ol (Z) in the solution were the most stable forms, most probably due to better hydrogen bonding. We also applied molecular docking modeling on the various tautomeric forms of the ligand as well as the complex with the main protease (6LU7) of the SARS-CoV-2 virus. Based on the obtained results, the complex had better interactions with the receptor. The order of the interactions was [Cu2L2(μ-OAc)2] > amine-one (Z) > imine-one (E) > imine-ol (Z) > amine-one (E) > imine-one (Z) > imine-ol (E).

Synthesis of novel mesoporous silica nanoparticles functionalized with succinic dihydrazone Schiff-base metal complexes and a study of their biological activities

For the first time, functionalized mesoporous silica nanoparticles (MSNs) with dinuclear Schiff-base complexes were synthesized as attractive organic–inorganic hybrids and their capability investigated for loading antibiotic drugs and immobilization of enzymes.

Cu(II)-Dy(III) and Co(III)-Dy(III) based single molecule magnets with multiple slow magnetic relaxation processes in the Cu(II)-Dy(III) complex.

Two dinuclear Schiff-base complexes [Cu(II)Dy(III)] and [Co(III)Dy(III)] have been synthesized and structurally characterized. The AC susceptibility measurements taken at BDC = 0.2 T show a slow magnetic relaxation typical for single-molecule magnets. Unusual is the presence of three relaxation branches in [Cu(II)Dy(III)]; the slowest (low-frequency) process possesses the barrier to spin reversal of U/kB = 2.8 K and an extrapolated relaxation time as slow as τ0 = 0.11 s. The intermediate-frequency process is typical for SMM of this class with U/kB = 122 K and τ0 = 9.9 × 10(-7) s; an onset of the high-frequency process is evidenced and this is the fastest. In contrast, the [Co(III)Dy(III)] complex free of exchange coupling exhibits only a single relaxation path with SMM parameters U/kB = 113 K and τ0 = 7.0 × 10(-9) s.

The first Mn–Zn heterometallic dinuclear compound based on Schiff base ligand N, N′-bis(salicylidene)-1,3-diaminopropane

Abstract One new heterometallic dinuclear Schiff-base complex Mn(DMF)2Zn(salpn)Cl2 (1) (H2salpn = N,N′-bis(salicylidene)-1,3-diaminopropane) has been successfully constructed by the solvothermal reaction of Mn(ClO4)2, ZnCl2 and H2salpn, and characterized by element analysis, IR spectroscopy and thermal analysis, as well as single crystal X-ray diffraction. The result reveals that compound 1 is heterodinuclear with Mn2+ and Zn2+ centers, in which they respectively present octahedral and tetrahedral coordination geometries. Each neutral molecule unit [Mn(DMF)2Zn(salpn)Cl2] is further connected by four intermolecular hydrogen bonding C H⋅⋅⋅Cl and two C H⋅⋅⋅O interactions from six adjacent units to form a three-dimensional supramolecular network with pcu α-Po 412⋅ 63 topology. Moreover, luminescence, antifungal and antimicrobial activities of the heteronuclear compound 1 have also been investigated.

Oxidation of Cyclohexene with Oxygen Catalyzed by Supported Dinuclear Schiff-Base Complex

Oxidation of cyclohexene, using chloromethylated polystyrene supported dinuclear Schiff-base complexes (PS-DD-M, where M= Cu2+, Co2+, Ni2+ and Mn2+, respectively) as catalyst and molecular oxygen as oxidant, was studied. In the oxidation reaction, cyclohexene was oxidized to 7-oxabicyclo[4,1,0]heptane, 2-cyclohexene-1-ol, 2-cyclohexene-1-one and 2-cyclohexene-1-hydroperoxide. It was found that the conversion of cyclohexene decreases in the order of PS-DD-Cu> PS-DD-Mn>PS-DD-Co>PS-DD-Ni, but the turnover number decreases with PS-DD-Ni>PS-DD-Mn>PS-DD-Co>PS-DD-Cu. A maximum conversion of 43% was observed for PS-DD-Cu/O2 system after a reaction of 10 h at 343 K as catalyst: substrate = 2 mg: 2 mL.

Two dinuclear Schiff-base complexes: synthesis, characterization, and biological activity

Two complexes, [Zn2L(µ-OAc)](ClO4) (1) and [Mn2L(OAc)2] · 4H2O (2), were synthesized by [2 + 2] cyclo-condensation between 2,6-diformyl-4-fluorophenol and 1,3-propyldiamine in the presence of metal ions M(II) (M = Zn and Mn), and were characterized by chemical analyses, IR spectra, electrospray mass spectra, and X-ray determinations. The results show that 1 forms dimers through hydrogen bonding. In 2, lattice waters, forming a 1-D water chain, function as glue to form a 3-D supramolecular network through extended hydrogen bonding. pBR322 plasmid DNA can be transformed to nicked form in air by 1 or nicked and linear forms in air by 2. Moreover, their antibacterial activities against S. aureus were investigated using penicillin as reference system.

Übergangsmetallkomplexe mit Schwefelliganden, CXXXIII [1]. Synthese, Struktur und Eigenschaften neuer FeII-Komplexe mit [FeN2S2]-Gerüsten / Transition Metal Complexes with Sulfur Ligands, CXXXIII [1]. Synthesis, Structure, and Properties of New FeII Complexes with [Fe2N2S2] Cores

Abstract In order to obtain suitable precursors for iron complexes that model the reactivity of the active sites of nitrogenases, the coordination chemistry of the [Fe(′N2H2S2′)] fragment was systematically investigated(′N2H2S2′2- = 1,2-ethanediamine-N,N′-bis(2-benzenethiolate)(2-)). One-pot reactions of FeCl2 -4H2O with the tetradentate amine-thiolate ligand ′N2H2S2′2- and CO, PR3 or P(OR)3 yielded the complexes [Fe(CO)2(′N2H2S2′)] (1), [Fe(CO)(PR3)(′N2H2S2′)] (R = Et (2), Pr (3), Bu (4)), [Fe(PMe3)2 (′N2H2S2′)] (7), [Fe(dppe)(′N2H2S2′)] (8 , dppe = 1,2- bis(diphenylphosphine)ethane), and [Fe(P(ÖR)3)2(′N2H2S2′)l (R = Me (9), Pr (10)). Mixed phosphane/phosphite complexes [Fe(PMe3)(P(OR)3)(′N2H2S2′)] (R = Me (11), Pr (12)) were synthesized by PMe3/P(OPr)3 exchange of the labile complexes [Fe(PMe3 )2(′N2H2S2′)] (7) and [Fe(P(OPr)3)2(′N2H2S2′)] (10). The [Fe(CO)(PR3)(′N2H2S2′)l complexes 3 and 4 also resulted from 1 and PR3 by photochemical CO substitution. They exhibit characteristic low-frequency v (CO) bands ( ≈1925 cm-1), and their remaining CO ligand proved photolytically inert. Reaction of 3 or 4 with NOBF4 yielded the dinuclear NO complex [Fe(NO)(′N2HS2′)]2 (6 ) which contains two amide functions. Contrary to expectations, [Fe(PR3)2(′N2H2S2′)l complexes could not be obtained with monodentate phosphanes other than PMe3. The corresponding N-methylated ligand ′N2Me2S2,2- yielded only the complexes [Fe(CO)2 (′N2Me2S2′)] (15) and [Fe(′N2Me2S2′)] (16). X-ray structure analyses of complexes 7, 8 -MeOH, 3, [Fe(CO)(dppm)(′N2H2S2 ′)]·0,5 THF (5 ·0,5THF, dppm = bis(diphenylphosphino)methane), and 12·0,5′N2 H2S2 ′-H2 confirm the pseudo-octahedral coordination of the Fe centers by two trans-S and two cis-N donors and two c/s-coligands. The structural data further suggest that the unexpected instability of the [Fe(PR3)2 (′N1H2S2′)] complexes is not caused by steric but by electronic effects. The cyclic voltammograms and the reactivity of the [Fe(L)(L′)(′N2H2S2′)] complexes corroborate this assumption. The oxidation behaviour of the [Fe(L)(L′)(′N2H2S2′)] complexes depends critically on the coligands L and L′. Reaction of 1 with dioxygen leads to oxidative dehydrogenation of the ′N2H2S2′2- ligand and yields the dinuclear Schiff-Base complex [Fe(′gma′ )]2 (′gma′2- = glyoxal-bis(2- mercaptoanil)(2-)). In contrast, oxidation of [Fe(CO)(PR3)(′N2H2S2′)], [Fe(PR3)2 (′N2H2S2′)] and [Fe(P(OR)3)2 (′N2H2S2)] complexes by dioxygen occurs metal-centered and gives the Fe(IV) complexes [Fe(PR3)(′N2S2′)] (R = Me, Pr), [Fe(P(OR)3)(′N2S2′)] (R = Me) and [Fe(′N2S2′)]2 that contain the tetraanionic thiolate-amide ligand ′N2S2′4-.