Dy2 and Dy4 hydroxo clusters assembled using o-vanillin based Schiff bases as ligands and b-diketone co-ligands: Dy4 cluster exhibits slow magnetic relaxation

The reaction of DyCl3.6H2O with the mixed ligand system consisting of o-vanillin based Schiff base ligand H2L [2-(2-hydroxy-3-methoxybenzylideneamino) phenol], dibenzoylmethane (Ph2acac) and acetylacetone (Acac) in the presence of triethylamine as the base afforded, di and tetranuclear dysprosium hydroxo clusters having formulae [Dy2(L)2(Ph2acac)2(H2O)2]3 (1) and [Dy4(L)4(acac)2(OH)2(H2O)2(C6H5N)4] (2) respectively. The solid state structures of these products were established by Single Crystal X-ray diffraction technique. Magnetism studies reveal Dy4 exhibits slow magnetic relaxation behavior

Визначення комплексоутворювальної здатності змішанолігандних органічних систем по відношенню до йонів металів

It is shown that classical and specific methods for determining the complex forming ability of mixed-ligand organic systems relative to the metal ions is not perfect. Determination of complex-forming ability of mixed-ligand organic systems relative to the metal ions using the method of turbidimetry for media containing biometal chlorides, mixed-ligand systems and sodium carbonate is proposed. As mixed-ligand systems used the culture fluid Bifidobacterium bifidum AC-1670 (mixed-ligand system I), the culture fluid of the composition of probiotic bacteria (mixed-ligand system II), the culture fluid of the composition of probiotic bacteria with the introduction of exogenous chelating agents (mixed-ligand system III), culture fluid of probiotic bacteria composition and products of their cell walls processing (mixed-ligand system IV). A solution of metal chloride (magnesium or calcium, or cuprum, or manganese, or ferrum or zinc) was added discretely to the aliquots of the solution of the organic mixed-ligand system. The mixture was stirred and kept for 30 minutes at 40 °C, then a solution of sodium carbonate was added to the aliquots and discretely measured turbidity of the solution by turbidimetric method at a wavelength of 450 nm. When the increasing of the turbidity magnitude system by 0.02 opt. un, a conclusion about the maximum value of the mixed-ligand organic systems complex forming capacity relative to the metal ion was made. Further increase in the turbidity of the system indicates an increase in the metal content in inorganic form, respectively the complex formation potential of the mixed-ligand system is exhausted. It is determined that the highest complex forming ability in relation to ions of biometals has mixed-ligand system III. The proposed method allows precisely to determine the complex formation capacity of mixed-ligand organic systems in relation to metal ions without the use of aggressive reagents capable of destroying chelate bonds and without involving high-cost rare equipment.Показано, що класичні та специфічні методи визначення комплексоутворювальної здатності змішанолігандних органічних систем по відношенню до йонів металів є не досконалими. Запропоновано визначення комплексоутворювальної здатності змішанолігандних органічних систем по відношенню до йонів металів із залученням методу турбідіметрії для середовищ, що містять хлориди біометалів, змішанолігандні системи та натрію карбонат. У якості змішанолігандних систем використовували культуральну рідину Bifidobacterium bifidum AC-1670 (змішанолігандна система І), культуральну рідину композиції пробіотичних бактерій (змішанолігандна система ІІ), культуральну рідину композиції пробіотичних бактерій із введенням екзогенних комплексонів (змішанолігандна система ІІІ), культуральну рідину композиції пробіотичних бактерій та продукти переробки їхніх клітинних стінок (змішанолігандна система ІV). До аліквот розчину органічної змішанолігандної системи дискретно додавали розчин хлориду металу (магнію, або кальцію, або купруму, або мангану, або феруму, або цинку), суміш перемішували та витримували протягом 30 хв за температури 40°С, після цього до аліквот додавали розчин натрію карбонату та дискретно вимірювали мутність розчину турбідіметричним методом при довжині хвилі 450 нм. При збільшенні величини мутності системи на 0,02 опт. од., робили висновок про максимальну величину комплексоутворювальної ємності змішанолігандної органічної систем по відношенню до йону металу. Подальший приріст мутності системи свідчить про збільшення вмісту металу в неорганічній формі, відповідно, комплексоутворювальний потенціал змішанолігандної системи – вичерпано. Визначено, що найвищою комплексоутворювальною здатністю по відношенню до йонів біометалів володіє змішанолігандна система ІІІ. Запропонований метод дозволяє точно визначити комплексоутворювальну ємність змішанолігандних органічних систем по відношенню до йонів металів без використання агресивних реактивів, здатних до руйнуваня хелатних зв’язків та без залучення високовартісного рідкісного обладнання

Formation of Fe(III) Ternary Complexes with Related Bio-relevant Ligands

Ternary complexes of iron(III)‐glycine( Gly)‐nitrilotriacetate (NTA) system determined by electrochemical measurements of the dissolved iron(III)‐Gly‐NTA mixed ligand system in the 0.1 mol·dm–3 NaClO4 aqueous solution at pH = 8.0 ± 0.1and 25 ± 1°C. The coordination number of Fe in Fe(EDTA)‐L is seven in coordinate complex, where L can be a DNA constituent like uracil, uridine, thymine, thymidine, and inosine. The nonlinear least‐squares program MINIQUAD‐75 is used to deduce the hydrolysis constants of [Fe(EDTA)(H2O)]− and its formation constant in solution. The antimicrobial activity of Fe(III) complexes of salicylhydroxamic acid (SHAM) and 1,10‐phenanthroline (PHEN) studied against representative pathogenic bacteria and fungi

Elektrokemijska karakterizacija miješanih kompleksa željeza(III) s glicinom i nitrilotriacetatom i njihova stabilnost u vodenim otopinama

Electrochemical characterization of iron(III)–glycine–nitrilotriacetate (iron(III)-Gly-NTA) mixed ligand complexes and determination of their stability constants and retention time in aqueous solutions (I = 0.1 mol dm–3 in NaClO4, pH = 8.0±0.1 at 25±1 °C), using differential pulse cathodic voltammetry (DPCV), cyclic voltammetry (CV) and direct current (d.c.) polarography with a static mercury drop electrode (SMDE), were performed. Iron(III) concentrations were varied from 5×10–6 to 6×10–4 mol dm–3, NTA total concentrations varied from 2×10–5 to 1×10–3 mol dm–3 and glycine total concentrations were 0.2, 0.02 and 0.002 mol dm–3. Iron(III) redox reaction in the mixed ligand system (by the techniques employed) was found to be a one-electron reversible process. At total concentration ratios of 1 : 800 : 2 for iron(III), glycine and NTA, respectively, the iron(III)-Gly-NTA mixed ligand complexes were dissolved and stable (>18 hours) in the aqueous solution. The complexes were formed either by the addition of NTA into the iron(III) and glycine aqueous solution or by the addition of iron(III) to the mixture of glycine and NTA. Under these conditions, iron(III) hydrolysis was highly suppressed. By fitting of experimental data, the following stability constants for mixed ligand complexes, not found in the literature so far, in 0.1 mol dm–3 NaClO4 aqueous solution were calculated: for iron(III) log β1([FeGlyNTA]) = 27.23±0.69, log β2([Fe(Gly)2NTA]2–) = 30.29±0.77; for iron(II) log β 1([FeGlyNTA]2–) = 14.13±0.43 and log β 2([Fe(Gly)2NTA]3–) = 18.51±0.51.Elektrokemijski su karakterizirani miješani kompleksi željeza(III) s glicinom i nitrilotriacetatom (FeIIIGly- NTA), te su određene njihove konstante stabilnosti i vrijeme zadržavanja u vodenim otopinama (I = 0,1 mol dm–3 u NaClO4, pH = 8,0±0,1 pri 25±1 °C) diferencijalnom pulsnom katodnom voltametrijom (DPKV), cikličkom voltametrijom (CV), te polarografijom s izravnim uzorkovanjem struje na elektrodi s visećom živinom kapi. Koncentracije željeza(III) mijenjane su od 5×10–6 do 6×10–4 mol dm–3, ukupne koncentracije NTA od 2×10–5 do 1×10–3 mol dm–3, dok su ukupne koncentracije glicina bile 0,2, 0,02 i 0,002 mol dm–3. Redoks reakcija željeza( III) u sustavu miješanih liganada (uporabljenim tehnikama) bila je jednoelektronski reverzibilni proces. Pri omjeru totalnih koncentracija 1 : 800 : 2 (željezo : glicin : NTA), FeIIIGlyNTA kompleksi su otopljeni i stabilni (>18 sati) u vodenoj otopini. Kompleksi su formirani kako dodatkom NTA u vodenu otopinu željeza(III) i glicina tako i dodatkom željeza(III) u smjesu glicina i NTA. Pod ovim uvjetima hidroliza željeza(III) je u većoj mjeri spriječena. Primjenom eksperimentalnih podataka izračunate su konstante stabilnosti kompleksa miješanih liganada u 0,1 mol dm–3 NaClO4, koje do sada nisu opisane u literaturi: za željezo(III) log β1([FeGlyNTA]–) = 27,23±0,69 i log β 2([Fe(Gly)2NTA]2–) = 30,29±0,77; za željezo(II) log β1([FeGlyNTA]2–) = 14,13±0,43 i log β2([Fe(Gly)2NTA]3–) = 18,51±0,51

A two-fold interpenetrated flexible bi-pillared-layer framework of Fe(II) with interesting solvent adsorption property

A two-fold interpenetrated microporous bi-pillared-layer framework of Fe(II), {[Fe(2,6- napdc)(4,4′ -bipy)](EtOH)(H2O)}n (1) (2,6-napdc = 2,6-naphthalenedicarboxylate; 4,4′ -bipy = 4,4′ -bipyridine) composed of mixed ligand system has been synthesized and structurally characterized. The 2,6-napdc linkers form a 2D corrugated sheet of {Fe(2,6-napdc)}n by linking the secondary building unit of Fe2(CO2)2 in the ac plane, which are further connected by double 4,4′ -bipy pillars resulting in a bi-pillared-layer type 3D framework. The 3D framework is two-fold interpenetrated and exhibits a 3D channel structure (4.0 × 3.5, 1.5 × 0.5 and 2.2 × 2.1 Å2) occupied by the guest water and ethanol molecules. Framework 1 shows high thermal stability, and the desolvated framework (1 ) renders permanent porosity realized by N2 adsorption pro- file at 77 K (BET surface area of ∼52 m2 g-1). Moreover, the framework 1 also uptakes different solvent vapours (water, methanol and ethanol) and their type-I profile suggest strong interaction with pore surfaces and overall hydrophilic nature of the framework. Temperature dependent magnetic measurements suggest overall antiferromagnetic behaviour in compound 1

Quantum Chemical Modeling of Pressure-Induced Spin Crossover in Octahedral Metal-Ligand Complexes.

Spin state switching on external stimuli is a phenomenon with wide applicability, ranging from molecular electronics to gas activation in nanoporous frameworks. Here, we model the spin crossover as a function of the hydrostatic pressure in octahedrally coordinated transition metal centers by applying a field of effective nuclear forces that compress the molecule towards its centroid. For spin crossover in first-row transition metals coordinated by hydrogen, nitrogen, and carbon monoxide, we find the pressure required for spin transition to be a function of the ligand position in the spectrochemical sequence. While pressures on the order of 1 GPa are required to flip spins in homogeneously ligated octahedral sites, we demonstrate a fivefold decrease in spin transition pressure for the archetypal strong field ligand carbon monoxide in octahedrally coordinated Fe2+ in [Fe(II)(NH3 )5 CO]2+

Synergic Extraction of Titanium (IV) with the New Solvent Tri-iso-amyl Phosphate (TAP) and Thenoyltrifluoroacetone (TTA)

The extraction of Ti (IV) from aqueous hydrochloric acid solution was investigated by using three different solvent systems: thenayltrifluoroacetone (TTA), a new solvent tn-iso-amyl phosphate (TAP)and a mixture of TTA and TAP, all diluted with carbon tetrachloride. An optimum of 90.34% and 97.45 % Ti(IV) was extracted when 4.0 % TTA or 33 % TAP was used, respectively. However, a significant synergic effect was observed even when half the concentration of the two extractants was used, i.e. a mixture of only 2.0% TTA and 16.0% TAP solution extracted as much as 99.03% of the metal from the aqueous HCl solutions. For all these three extraction systems concentrations of Ti(IV) and HCl were maintained at 1. 0 x 10J mol [1 and 11.5 mol [1, respectively. It was concluded that Ti(IV) forms a disolvate with both the ligands, i.e. TTA and TAP, but a 1:1 mixed solvate is formed when a TTA-TAP mixed ligand system is used. It was also established that the TTA combines in its undissociated form with the central metallic ion Ti(IV). The mathematical treatment ofthe three extraction systems showed that the average values of log Kafor the three systems were 2.48 (TTA), 1.60 (TAP) and 3.19 (TTATAP synergic system). It was also shown that the experimental value for the mixed solvate system is 7.06 times higher than the statistically evaluated value for the same system