Search results for "Schiff Base"
showing 10 items of 180 documents
Synthesis and antimicrobial screening of tetra Schiff bases of 1,2,4,5-tetra (5-amino-1,3,4-thiadiazole-2-yl)benzene
2014
Abstract In the present study, novel tetra Schiff bases were synthesized by condensation of 1,2,4,5-tetra (5-amino-1,3,4-thiadiazole-2-yl)benzene with different aromatic aldehydes. The chemical structures were confirmed by means of IR, 1 H NMR, 13 C NMR, and elemental analysis. All compounds were screened for antibacterial ( Staphylococcus aureus ATCC-9144, Staphylococcus epidermidis ATCC-155, Micrococcus luteus ATCC-4698, Bacillus cereus ATCC-11778, Escherichia coli ATCC-25922, and Pseudomonas aeruginosa ATCC-2853) and antifungal ( Aspergillus niger ATCC-9029 and Aspergillus fumigatus ATCC-46645) activities by paper disc diffusion technique. The minimum inhibitory concentrations (MICs) of …
Magnetic Properties of End-to-End Azide-Bridged Tetranuclear Mixed-Valence Cobalt(III)/Cobalt(II) Complexes with Reduced Schiff Base Blocking Ligands…
2019
Two tetranuclear mixed-valence cobalt(III/II) complexes having the general formula [(μ1,3-N3){CoII(Ln)(μ-O2CC6H4NO2)CoIII(N3)}2]PF6 (where H2L1 and H2L2 are two reduced Schiff base ligands) have been synthesized and characterized. The structures of both complexes show cobalt(II) and cobalt(III) centers with a distorted octahedral geometry with cobalt(III) and cobalt(II) centers located at the inner N2O2 and outer O4 cavities of the reduced Schiff base ligands, respectively. The oxidation states of both cobalt centers have been confirmed by bond valence sum (BVS) calculations. The magnetic properties show that both compounds behave as cobalt(II) dimers connected through an end-to-end azido b…
Spectroscopic study of the interaction of Ni(II)-5-triethyl ammonium methyl salicylidene ortho-phenylendiiminate with native DNA.
2009
The interaction of native calf thymus DNA with the cationic Ni(II) complex of 5-triethyl ammonium methyl salicylidene ortho-phenylendiimine (NiL(2+)), in 1mM Tris-HCl aqueous solutions at neutral pH, has been monitored as a function of the metal complex-DNA molar ratio by UV absorption spectrophotometry, circular dichroism (CD) and fluorescence spectroscopy. The dramatic modification of the DNA CD spectrum, the appearance of a broad induced CD band in the range 350-400nm, the strong increase of the DNA melting temperature (T(m)) and the fluorescence quenching of ethidium bromide-DNA solutions, in the presence of increasing amounts of the NiL(2+) metal complex, support the existence of a tig…
The interaction of Schiff Base complexes of nickel(II) and zinc(II) with duplex and G-quadruplex DNA
2017
The duplex and G-quadruplex DNA-binding of six nickel(II) and zinc(II) complexes of three salphen-like ligands (salphen = N,N?-bis-salicylidene-1,2-phenylenediaminato) was investigated by UV-visible absorption and circular dichroism spectroscopy. The results obtained, in particular the values of the DNA-binding constants, Kb, point out that the nickel(II) complexes show a higher affinity toward both duplex and G-quadruplex DNA, compared to the analogous zinc(II) complexes. Interestingly, the zinc(II) complexes possess high selectivity toward G-quadruplex DNA, being negligible their binding with duplex DNA. Molecular dynamics (MD) simulations provided atomistic models for the interpretation …
The interaction of native DNA with iron(III)- N ,N'-ethylene-bis(salicylideneiminato)-chloride.
2004
Abstract The interaction between native calf thymus deoxyribonucleic acid (DNA) and Fe III - N , N ′ -ethylene-bis (salicylideneiminato)-chloride, Fe(Salen)Cl, was investigated in aqueous solutions by UV–visible (UV–vis) absorption, circular dichroism (CD), thermal denaturation and viscosity measurements. The results obtained from CD, UV–vis and viscosity measurements exclude DNA intercalation and can be interpreted in terms of an electrostatic binding between the Fe(Salen) + cation and the phosphate groups of DNA. The trend of the UV–vis absorption band of the Fe(Salen)Cl complex at different ratios [DNA phosphate ]/[Fe(Salen)Cl] and the large increase of the melting temperature of DNA in …
The interaction of native DNA with Zn(II) and Cu(II) complexes of 5-triethyl ammonium methyl salicylidene orto-phenylendiimine
2007
The interaction of native calf thymus DNA with the Zn(II) and Cu(II) complexes of 5-triethyl ammonium methyl salicylidene orto-phenylendiimine (ZnL(2+) and CuL(2+)), in 1 mM Tris-HCl aqueous solutions at neutral pH, has been monitored as a function of the metal complex-DNA molar ratio by UV absorption spectrophotometry, circular dichroism (CD) and fluorescence spectroscopy. The results support for an intercalative interaction of both ZnL(2+) and CuL(2+) with DNA, showing CuL(2+) an affinity of approximately 10 times higher than ZnL(2+). In particular, the values of the binding constant, determined by UV spectrophotometric titration, equal to 7.3x10(4) and 1.3x10(6)M(-1), for ZnL(2+) and CuL…
Another step toward DNA selective targeting: NiII and CuII complexes of a Schiff base ligand able to bind gene promoter G-quadruplexes
2016
DNA G-rich sequences are able to form four-stranded structures organized in stacked guanine tetrads. These structures, called G-quadruplexes, were found to have an important role in the regulation of oncogenes expression and became, for such a reason, appealing targets for anticancer drugs. Aiming at finding selective G-quadruplex binders, we have designed, synthesized and characterized a new water soluble Salen-like Schiff base ligand and its NiII and CuII metal complexes. UV-Vis, circular dichroism and FRET measurements indicated that the nickel complex can stabilize oncogene promoter G-quadruplexes with high selectivity, presenting no interactions with duplex DNA at all. The same compoun…
Formation of a novel ferromagnetic end-to-end cyanate bridged homochiral helical copper(ii) Schiff base complex via spontaneous symmetry breaking
2014
A homochiral helical coordination polymer of copper(II) has been synthesized using achiral precursors via spontaneous symmetry breaking and has been confirmed by single crystal X-ray diffraction and solid-state CD spectroscopy. The variable temperature magnetic measurements indicate the presence of weak ferromagnetic exchange interactions mediated by end-to-end cyanate bridges (J = +0.12 cm(-1)).
Nickel(II), copper(II) and zinc(II) metallo-intercalators: structural details of the DNA-binding by a combined experimental and computational investi…
2014
We present a thorough characterization of the interaction of novel nickel(II) (1), copper(II) (2) and zinc(II) (3) Schiff base complexes with native calf thymus DNA (ct-DNA), in buffered aqueous solution at pH 7.5. UV-vis absorption, circular dichroism (CD) and viscometry titrations provided clear evidence of the intercalative mechanism of the three square-planar metal complexes, allowing us to determine the intrinsic DNA-binding constants (K(b)), equal to 1.3 × 10(7), 2.9 × 10(6), and 6.2 × 10(5) M(-1) for 1, 2 and 3, respectively. Preferential affinity, of one order of magnitude, toward AT compared to GC base pair sequences was detected by UV-vis absorption titrations of 1 with [poly(dG-d…
Synthesis and characterization of vanadyl(IV) complexes of Schiff bases derived from anthranilic acid and salicylaldehyde (or its derivatives) or ace…
1997
Anhydrous, dimeric vanadyl(IV) complexes of Schiff bases derived from [1+1] condensation of salicylaldehyde (or its derivatives) and anthranilic acid, have been synthesized from CH3CN and were characterized by elemental analysis, FTIR, EPR, absorption, TGA, cyclic voltammetry and room temperature magnetic susceptibility measurements. These complexes were found to be oxidized by air in polar solvents like MeOH and DMF to V-V products. The E(1/2) values were found to be around 660 mV indicating that the carboxylate group favours vanadyl(IV) binding when compared to the alkoxo-bound vanadium complexes. Oxidative instability of these complexes are dependent on the substituent on the salicylalde…