Conductometric study of complexation reaction of 4′-nitrobenzo-15-crown-5 with Mn+2, Co+2, Y+3, and ZrO+2 cations in acetonitrile,methanol and their binary solvent solutions

The complexation reactions of Mn²⁺, Co²⁺, Y³⁺, and ZrO²⁺ cations with the macrocyclic ligand, 4′-nitrobenz-15-crown-5 (4′-NB15C5), in acetonitrile (AN), methanol and AN-MeOH binary mixtures have been studied at various temperatures using the conductometric method. The conductance data stand for the Me : L stoichiometric ratio 1 : 1. Values of the formation constants of the complexes were accumulated by plotting molar conductivity curves using the computer program, GENPLOT. The order of stability of the metal-ion complexes in pure AN at 15°C was found to be: (4′-NB15C5 · ZrO)²⁺ > (4′-NB15C5 · Mn)²⁺ ≈ (4′-NB15C5 · Co)²⁺ > (4′-NB15C5 · Y)³⁺. In the case of AN-MeOH binary solvent solutions with 50 and 75 mole percent of AN at the same temperature, the sequence of stability of the complexes was the following: (4′-NB15C5 · Mn)²⁺ > (4′-NB15C5 · ZrO)²⁺ ≈ (4′-NB15C5 · Co)²⁺ 〉 (4′-NB15C5 · Y)³⁺, and (4′-NB15C5 · Mn)²⁺ > (4′-NB15C5 · Y)³⁺ ≈ (4′-NB15C5 · Co)²⁺ > (4′-NB15C5 · ZrO)²⁺, respectively. The complexes formed are entropy stabilized in all cases.     

Study of complex formation between 18-crown-6 and diaza-18-crown-6 with uranyl cation (UO2 2+) in some binary mixed aqueous and non-aqueous solvents

The complexation reaction between UO₂ ²⁺ cation with macrocyclic ligand, 18-crown-6 (18C6), was studied in acetonitrile–methanol (AN–MeOH), nitromethane–methanol (NM–MeOH) and propylencarbonate–ethanol (PC–EtOH) binary mixed systems at 25 °C. In addition, the complexation process between UO₂ ²⁺ cation with diaza-18-crown-6 (DA18C6) was studied in acetonitrile–methanol (AN–MeOH), acetonitrile–ethanol (AN–EtOH), acetonitrile–ethylacetate (AN–EtOAc), methanol–water (MeOH–H₂O), ethanol–water (EtOH–H₂O), acetonitrile–water (AN–H₂O), dimethylformamide–methanol (DMF–MeOH), dimethylformamide–ethanol (DMF–EtOH), and dimethylformamide–ethylacetate (DMF–EtOAc) binary solutions at 25 °C using the conductometric method. The conductance data show that the stoichiometry of the complexes formed between (18C6) and (DA18C6) with UO₂ ²⁺ cation in most cases is 1:1 [M:L], but in some solvent 1:2 [M:L₂] complex is formed in solutions. The values of stability constants (log K_f) of (18C6 · UO₂ ²⁺) and (DA18C6 · UO₂ ²⁺) complexes which were obtained from conductometric data, show that the nature and also the composition of the solvent systems are important factors that are effective on the stability and even the stoichiometry of the complexes formed in solutions. In all cases, a non-linear relationship is observed for the changes of stability constants (log K_f) of the (18C6 · UO₂ ²⁺) and (DA18C6 · UO₂ ²⁺) complexes versus the composition of the binary mixed solvents. The stability order of (18C6 · UO₂ ²⁺) complex in pure studied solvents was found to be: EtOH > AN ≈ NM > PC ≈ MeOH, but in the case of (DA18C6 · UO₂ ²⁺) complex it was : H₂O > MeOH > EtOH.     

Solvent influence upon complexation of N-phenylaza-15-crown-5 with UO2 2+ cation in binary mixed non-aqueous solvents

The complexation reaction of N-phenylaza-15-crown-5 (PhA15C5) with UO₂ ²⁺ cation was studied in acetonitrile–methanol (AN–MeOH), acetonitrile–butanol (AN–BuOH), acetonitrile–dimethylformamide (AN–DMF) and methanol–propylencarbonate (MeOH–PC) binary solutions, at different temperatures by conductometry method. The conductance data show that the stoichiometry of the complex formed between PhA15C5 with UO₂ ²⁺ cation in most cases is 1:1 [M:L], but in some solvent systems a 1:2 [M:L₂] complex is formed in solutions. The results revealed that, the stability constant of (PhA15C5·UO₂)²⁺ complex in the binary mixed solvents varies in the order: AN–BuOH>AN–MeOH>AN–DMF. In the case of the pure organic solvents, the sequence of the stability of the complex changes as: AN>PC>BuOH>DMF. A non-linear relationship was observed for changes of logK_f of (PhA15C5·UO₂)²⁺ complex versus the composition of the binary mixed solvents. The corresponding standard thermodynamic parameters (ΔH_c°, ΔS_c°) were obtained from temperature dependence of the stability constant. The results show that the values and also the sign of these parameters are influenced by the nature and composition of the mixed solvents.     

Solvent influence upon complex formation between benzo-15-crown-5 and Mg2+, Ca2+ and Sr2+ cations in some pure and binary mixed solvents using conductometric method

The complexation reactions between Mg²⁺, Ca²⁺ and Sr²⁺ cations with the macrocyclic ligand, benzo-15-crown-5 (B15C5), in pure acetonitrile, water, methanol and tetrahydrofuran and also in acetonitrile–water (AN–H₂O) and in methanol–tetrahydrofuran (MeOH–THF) binary mixtures have been studied at different temperatures using conductometric method. The conductance data show that the stoichiometry of the complexes in most cases is 1:1 [ML]. But in the case of Ca²⁺ cation a 1:2 [ML₂] complex is formed in pure THF, which shows that the stoichiometry of the complexes may be changed by the nature of the medium. The values of stability constants of complexes, which were obtained from conductometric data, show that the stability of complexes is affected by the nature and composition of the binary mixed solvents and a non-linear behavior was observed for variation of logK_f of the complexes versus the composition of the solvent systems. The results show that the selectivity order of B15C5 for the metal cations in two AN–H₂O binary solutions (mol% AN = 25.71 and 50.94) at 25 °C is: Mg²⁺ > Sr²⁺ > Ca²⁺. The values of thermodynamic parameters (ΔH _c ⁰ , ΔS _c ⁰ ) for formation of complexes were obtained from temperature dependence of stability constants of complexes using the van’t Hoff plots. The results show that the values and also the sign of these parameters are influenced by the nature and also the composition of the binary mixed solvents.     

Effect of solvent on the stability constant of complex formation and the thermodynamic parameters between dicyclohexyl-18-crown-6 with Eu3+, La3+, Er3+ and Y3+ cations

The complexation reaction between Eu³⁺, La³⁺, Er³⁺ and Y³⁺ cations with the dicyclohexyl-18-crown-6 (DCH18C6) in acetonitrile (AN)–dimethylformamide (DMF) and AN–methanol (MeOH) binary systems have been studied at different temperatures using conductometric method. The conductometric data show that the stoichiometry of the complexes is 1:1 [ML]. The results show that the stability constant of complexes in various solvents is: AN > MeOH > DMF. In the some cases, the minimum of logK_f for (DCH18C6–Eu³⁺), (DCH18C6–La³⁺), (DCH18C6–Er³⁺) and (DCH18C6–Y³⁺) complexes in AN–MeOH binary systems obtain at χ_MeOH ~ 0.75, and also, the logK_f of (DCH18C6–Er³⁺) complex in AN–DMF binary systems show a minimum at χ_AN ~ 0.75. Non-linear behavior was observed for the stability constant of complexes versus the composition of the solvent systems. The experimental data show that the selectivity order of DCH18C6 for these cations in AN–MeOH binary systems (mol% AN = 50, 75) at 25 °C is: Y³⁺ > Er³⁺ > Eu³⁺ > La³⁺. The values of thermodynamic parameters (?H?_C) for formation of complexes were obtained from temperature dependence of stability constants of complexes using the van′t Hoff plots and the standard entropy (?S?_C) were calculated from the relationship: ?G?_C, 298.15 = ?H?_C ?298.15?S?_C. The results show that the values of these thermodynamic parameters are influenced by the nature and the composition of the binary systems.     

Study of Complex Formation between N-Phenylaza-15-Crown-5 with Mg2+, Ca2+, Ag+ and Cd2+ Metal Cations in Some Binary Mixed Aqueous and Non-aqueous Solvents using the Conductometric Method

The complexation reactions between Mg²⁺, Ca²⁺, Ag⁺ and Cd²⁺ metal cations with N-phenylaza-15-crown-5 (Ph-N15C5) were studied in acetonitrile (AN)–methanol (MeOH), methanol (MeOH)–water (H₂O) and propanol (PrOH)–water (H₂O) binary mixtures at different temperatures using the conductometric method. The conductance data show that the stochiometry of all of the complexes with Mg²⁺, Ca²⁺, Ag⁺ and Cd²⁺ cations is 1:1 (L:M). The stability of the complexes is sensitive to the solvent composition and a non-linear behaviour was observed for variation of log K _f of the complexes versus the composition of the binary mixed solvents. The selectivity order of Ph-N15C5 for the metal cations in neat MeOH is Ag⁺>Cd²⁺>Ca²⁺>Mg²⁺, but in the case of neat AN is Ca²⁺>Cd²⁺>Mg²⁺>Ag⁺. The values of thermodynamic parameters (ΔH _c ^o , ΔS _c ^o ) for formation of Ph-N15C5–Mg²⁺, Ph-N15C5–Ca²⁺, Ph-N15C5–Ag⁺ and Ph-N15C5–Cd²⁺ complexes were obtained from temperature dependence of stability constants and the results show that the thermodynamics of complexation reactions is affected by the nature and composition of the mixed solvents.     

Spectroscopy studies on DNA binding of two ruthenium complexes [Ru(MeIm)4(L)]2+ (L = iip and tip)

Two ruthenium(II) complexes [Ru(MeIm)₄(L)]²⁺ (L?=?2-(imidazo-4-group)-1H-imidazo-[4,5-f][1,10]phenanthroline, 2-(thiophene-2-group)-1H-imidazo[4,5-f][1,10]phenanthroline, MeIm?=?1-methylimidazole) have been synthesized according to literature and structurally characterized. The interaction of the complexes with calf thymus DNA has been explored using electronic absorption titration, competitive binding experiment, circular dichroism, thermal denaturation, and viscosity measurements. The results show that both complexes could bind DNA in a intercalation mode and the DNA-binding affinity of [Ru(MeIm)₄(tip)]²⁺ (K _b?=?(7.2?±?0.3)?×?10⁵?(mol?L^?1)^?1) is greater than that of [Ru(MeIm)₄(iip)]²⁺ (K _b?=?(6.1?±?0.2)?×?10⁵?(mol?L^?1)^?1).     

NMR study of the stoichiometry and stability of complexation reaction between Mg2+, Ca2+, Sr2+ and Ba2+ ions and 60-crown-20 in binary acetonitrile solvent mixtures

Proton nuclear magnetic resonance (¹H-NMR) spectroscopy was used to study the complexation reaction between Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ ions and 60-crown-20 in a series of binary mixtures of deuterated acetonitrile (AN), nitromethane (NM) and D₂O at 27?°C. Formation constants of the 1:1 complexes were determined through computer fitting of the chemical shift/mol ratio data and found to vary in the order of Ba²⁺?>?Sr²⁺?>?Mg²⁺?≈?Ca²⁺. The influence of the solvent composition on the stability of the resulting complexes was also discussed. In all cases, the changes in the stability constants with the solvent composition were monotonic and showed a good correlation with the inherent solvation ability of the pure solvents which form the mixture.     

A thermodynamic study of interaction of Ag+, Mg2+, Ca2+, and K+ cations with 4-hydroxyphenyl-2,5-bis(2-benzofuranyl)pyridine in some binary mixed non-aqueous solvents

In the present work the complexation process between Ag⁺ and Mg²⁺ cations and 4-hydroxyphenyl-2,5-bis(2-benzofuranyl)pyridine (HBFPY) ligand was studied in pure dimethylformamide (DMF), ethanol (EtOH), acetonitrile (AN) and in (DMF-EtOH), (AN-EtOH) and (DMF-AN) binary mixed solvent solutions at different temperatures using the conductometric method. Also in this work the complexation reaction between Ca²⁺, K⁺ cations and HBFPY ligand, was studied in pure dimethylformamide (DMF), propanol (PrOH), 1,4-dioxane (DOX), ethanol (EtOH) and in DMF-PrOH, DMF-DOX and DMF-EtOH binary mixed solvent solutions at different temperatures using the conductometric method. The conductance data show that the stoichiometry of the complexes formed between this ligand and the studied cations is 1 : 1 [ML]. In most cases, addition of HBFPY to solutions of these cations, causes a continuous increase in the molar conductivities which indicates that the mobility of complexed cations is more than the uncomplexed ones. The stability constants of the complexes were obtained from fitting of molar conductivity curves using a computer program, GENPLOT. The stability constant of [Mg(HBFPY)]²⁺ complex in various neat solvents at 15°C decreases in order: EtOH > DMF > AN and the stability constant of [Ag(HBFPY)]⁺ complex in various neat solvents at 35°C decreases in order: DMF > EtOH. The values of standard enthalpy changes (ΔH° _c ) for complexation reactions were obtained from the slope of the Van’t Hoff plots and the changes in standard entropy (ΔS° _c ) were calculated from the relationship ΔH° _c,295.15= ΔH° _c –298.15ΔS° _c .     

A complexation study of 15-crown-5 with Co2+ cation in some pure and mixed organic solvents

The stability constant (log K _f) and the thermodynamic parameters (free energies, enthalpies, and entropies) of the complexation of Co²⁺ cation with 15-crown-5 (15C5) in acetonitrile-methanol (AN/MeOH), acetonitrile-nitrobenzene (AN/NB), acetonitrile-dichloromethane (AN/DCM) and acetonitrile-1,2-dichloroethane (AN/DCE) binary solvent solutions were calculated from the experimental conductance data at different temperatures. The complexation behavior of the crown ether used in these media was discussed in view of the estimated parameters. In all solvent systems, 15-crown-5 formed a 1: 1 complex with Co²⁺ cation. The stability order of (Co-15C5)²⁺ complex in the binary mixed solvents at 25°C was found to be: AN/NB > AN/DCM ≈ AN/DCE > AN/MeOH. In most cases, a non-linear relationship was observed for changes of log K _f of (Co-15C5)²⁺ complex versus the composition of the binary mixed solvent systems. The experimental results show that the standard thermodynamic parameters of the complexation process change with the nature and composition of the binary solvent solutions.     

Study of complexation process between 4′-nitrobenzo-15-crown-5 and yttrium(III) cation in binary mixed non-aqueous solvents using conductometric method

The complexation reaction of macrocyclic ligand (4??-nitrobenzo-15C5) with Y³⁺ cation was studied in acetonitrile-methanol (AN-MeOH), acetonitrile-ethanol (AN-EtOH), acetonitrile-dimethylformamide (AN-DMF) and ethylacetate-methanol (EtOAc-MeOH) binary mixtures at different temperatures using conductometry method. The conductivity data show that in all solvent systems, the stoichiometry of the complex formed between 4??-nitrobenzo-15C5 and Y³⁺ cation is 1: 1 (ML). The stability order of (4??-nitrobenzo-15C5). Y³⁺ complex in pure non-aqueous solvents at 25°C was found to be: EtOAc > EtOH > AN ?? DMF > MeOH, and in the case of most compositions of the binary mixed solvents at 25°C it was: AN??MeOH ?? AN-EtOH > AN-DMF > EtOAc-MeOH. But the results indicate that the sequence of the stability of the complex in the binary mixed solutions changes with temperature. A non-linear behavior was observed for changes of logK _f of (4??-nitrobenzo-15C5 · Y³⁺) complex versus the composition of the binary mixed solvents, which was explained in terms of solvent-solvent interactions and also the hetero-selective solvation of the species involved in the complexation reaction. The values of thermodynamic parameters (??H _c ^? and ??S _c ^? ) for formation of the complex were obtained from temperature dependent of the stability constant using the van??t Hoff plots. The results represent that in most cases, the complex is both enthalpy and entropy stabilized and the values and also the sign of thermodynamic parameters are influenced by the nature and composition of the mixed solvents.     

Study of complexation process between N-phenylaza-15-crown-5 with yttrium cation in binary mixed solvents

The complexation reaction between Y³⁺ cation with N-phenylaza-15-crown-5(Ph-N15C5) was studied at different temperatures in acetonitrile–methanol (AN/MeOH), acetonitrile–propanol (AN/PrOH), acetonitrile–1,2 dichloroethane (AN/DCE) and acetonitrile–water (AN/H₂O) binary mixtures using the conductometric method. The results show that in all cases, the stoichiometry of the complex is 1:1 (ML). The values of formation constant of the complex which were determined using conductometric data, show that the stability of (Ph-N15C5.Y)³⁺ complex in pure solvents at 25?°C changes in the following order: PrOH?>?AN?>?MeOH and in the case of binary mixed solutions at 25?°C it follows the order: AN–DCE?>?AN–PrOH?>?AN–MeOH?>?AN–H₂O. The values of standard thermodynamic quantities (?H _c ^° and ?S _c ^° ) for formation of (Ph-N15C5.Y)³⁺ complex were obtained from temperature dependence of the formation constant using the van’t Hoff plots. The results show that in most cases, the complex is entropy and enthalpy stabilized and these parameters are influenced by the nature and composition of the mixed solvents. In most cases, a non-linear behavior was observed for variation of log K_f of the complex versus the composition of the binary mixed solvents. In all cases, an enthalpy–entropy compensation effect was observed for formation of (Ph-N15C5.Y)³⁺ complex in the binary mixed solvents.     

Cuprous complexes and dioxygen,VII. Competition between one- and two-electron reduction of O2 in the autoxidation of Cu(1-methyl-2-hydroxymethyl-imidazole)2+

The complexation of 1-methyl-2-hydroxymethyl-imidazole (L) with Cu(I) and Cu(II) has been studied in aqueous acetonitrile (AN). Cu(I) forms three complexes, Cu(AN)L⁺, CuL₂⁺, and Cu(AN)H_?1L, with stability constants logK(Cu(AN)⁺ + L ? Cu(AN)L⁺) = 4.60 ± 0.02, logβ₂ = 11.31 ± 0.04, and logK(Cu(AN)H_?1L+H⁺ ? Cu(AN)L⁺) = 10.43 ± 0.08 in 0.15M AN. The main species for Cu(II) are CuL²⁺, CuH_?1L⁺, CuH_?1L₂⁺, and CuH_?2L₂. The autoxidation of CuL₂⁺ was followed with an oxygen sensor and spectrophotometrically. Competition between the formation of superoxide in a one-electron reduction of O₂ and a path leading to H₂O₂ via binuclear (CuL₂)₂O was inferred from the rate law with k_a = (2.31 ± 0.12) · 10⁴M ^?2S ^?1, k_b = (1.0 ± 0.2) · 10³M ^?1, k_c = (2.85 ± 0.07) · 10²M ^?2S ^?1, k_d = 3.89 ± 0.14M ^?1S ^?1, k_e = 0.112 ± 0.004, k_f = (2.06 ± 0.24) · 10^?10M S ^?1, k_g = (1.35 ± 0.07) · 10^?7 S ^?1, and k_h = (6.8 ± 1.4) · 10^?7M ^?1 S ^?1.     

Solvent influence on complex formation between Cd<Superscript>2+</Superscript> and 2-hydroxy-1,4-naphthoquinone in binary mixed nonaqueous solvents at 15–45°C

The complexation reaction of Cd²⁺ cation with 2-hydroxy-1,4-naphthoquinone (HNQ) was studied in acetonitrile (AN), 2-PrOH, ethyl acetate (EtOAc), EtOH, dimethylformamide (DMF) and in binary solutions AN–2-PrOH, AN–DMF, AN–EtOH, and AN–EtOAc using conductometric method at 15–45°C. The conductance data show that the stoichiometry of the Cd²⁺ complex with HNQ in all solvent systems is 1 : 1. In the pure solvents the stability of the complex changes in the order AN > 2-PrOH > EtOH > DMF. The stability of the complex at 25°C in the studied mixtures changes in the following order : AN?EtOAc > AN?2-PrOH > AN?EtOH > AN?DMF. These orders are affected by the nature and composition of the solvent systems and by the temperature. From the temperature dependence data, the thermodynamic functions values (ΔH° and ΔS°) for the complex formation were calculated.     

Synthesis and crystal structure of two praseodymium 2-iodobenzoic acid complexes

Two new complexes, {[Pr(2-IBA)₃?·?2,2′-bipy]₂·[Pr(2-IBA)₃?·?2,2′-bipy]₂?·?0.5C₂H₅OH?·?H₂O} (1) and [Pr(2-IBA)₃?·?phen]₂ (2) (2-IBA?=?2-iodobenzoate; 2,2′-bipy?=?2,2′-bipyridine; phen?=?1,10-phenanthroline) were synthesized, and their crystal structures were determined by X-ray diffraction. Complex 1 consists of two binuclear molecules [Pr(2-IBA)₃?·?2,2′-bipy]₂ (a) and [Pr(2-IBA)₃?·?2,2′-bipy]₂ (b), half uncoordinated ethanol and one uncoordinated water. In the two molecules (a) and (b), the coordination environment of central ions is similar. The Pr1³⁺ ion in molecule (a) and Pr2³⁺ ion in molecule (b) are nine-coordinate with seven oxygen atoms from five 2-IBA ligands and two nitrogen atoms from one 2,2′-bipy molecule. The crystal structure of complex 2 is similar to that of binuclear [Pr(2-IBA)₃?·?2,2′-bipy]₂ in complex 1.     

Supramolecular networks constructed by cationic copper(II) complexes incorporating hybrid water–anionic polymeric assemblies

Two complexes, [Cu₂(TFSA)(2,2′-bpy)₄]?·?TFSA?·?8H₂O (1) and {[Cu(4,4′-bpy)(H₂O)₂]?·?TFSA?·?6H₂O} _n (2) (H₂TFSA?=?tetrafluorosuccinic acid, 2,2′-bpy?=?2,2′-bipyridine, and 4,4′-bpy?=?4,4′-bipyridine), have been synthesized and structurally characterized by X-ray structural analyses. Complex 1 is a binuclear molecule bridged by TFSA ligands; 2 is a 1-D chain bridged by 4,4′-bpy ligands. The asymmetric units of the two complexes are composed of cationic complexes [Cu₂(TFSA)(2,2′-bpy)₄]²⁺ (1) and [Cu(4,4′-bpy)(H₂O)₂]²⁺ (2), free TFSA anion, and independent crystallization water molecules. A unique 2-D hybrid water–TFSA anionic layer by linkage of {[(H₂O)₈(TFSA)]^2?} _n fragments consisting of 1-D T6(0)A2 water tape and TFSA anionic units by hydrogen bonds in 1 was observed. Unique 2-D hybrid water–TFSA anionic layer generated by the linkage of {[(H₂O)₆(TFSA)]^2?} _n fragments consisting of cyclic water tetramers with appended water molecules and TFSA anionic units, and 1-D metal–water tape [Cu–H₂O?···?(H₂O)₆?···?H₂O^?] _n in 2 were found. 3-D supramolecular networks of the two complexes consist of cationic complexes and water–TFSA anionic assemblies connected by hydrogen bonds.     

Antibacterial,nuclease, and SOD-mimic behaviors of copper(II) complexes of norfloxacin and phenanthrolines

Square-pyramidal complexes [Cu(NFL)(A ⁿ )Cl]?·?5H₂O (A ^{n ?}=?phenanthroline derivatives and NFL?=?deprotonated norfloxacin) have been synthesized and characterized. Interactions with Herring Sperm DNA and pUC19 DNA have been investigated. Mode and extent of interaction was measured by the perturbation in absorbance of complexes in the absence and presence of DNA. Hydrodynamic volume change and gel electrophoretic results were also kept under consideration. Synthesized complexes bind to DNA via intercalation with binding constant 0.875–1.446?×?10⁴?(mol?L^?1)^?1 based on bathochromism and hypochromism observed. Intercalative binding of complexes with DNA was further supported by relative viscosity, where 5 intercalates more strongly with most increase in relative viscosity, and K _b value of 1.446?×?10⁴?(mol?L^?1)^?1. Evaluation of electrophoretic separation of plasmid on agarose gel reveals that 5 cleaves more efficiently. Square-pyramidal geometry at the metal center supports superoxide-dismutase (SOD)-mimic behavior in addition to an electron-withdrawing group on the ancillary ligand stabilizing Cu–O bonding.     

A thermodynamic study of complex formation between dicyclohexyl-18-crown-6 (DCH18C6) and La3+, UO 22+ , Ag+, and NH 4+ cations in acetonitrile-tetrahydrofuran binary media using conductometric method

The complex formation between La³⁺, UO₂²⁺ Ag⁺, and NH₄⁺ cations and macrocyclic ligand, dicyclohexyl-18-crown-6 (DCH18C6), was studied in acetonitrile-tetrahydrofuran (AN-THF) binary mixtures at different temperatures using the conductometric method. The results show that with the exception of complexation of the NH₄⁺ cation with DCH18C6 in pure acetonitrile, the stoichiometry of all the complexes is being 1: 1 (M: L). The stability constants of the complexes were determined using a GENPLOT computer program. The nonlinear behavior which was observed for changes of log K _f of the complexes versus the composition of the mixed solvent was discussed in terms of solvent-solvent interaction in their binary solution, which results in changing the chemical and physical properties of the constituent solvents when they mix with one another and, therefore, changing the solvation capacities of the metal cations, crown ether molecules, and even the resulting complexes with changing the mixed solvent composition. The results show that the selectivity of DCH18C6 for the studied cations changes with the composition of the AN-THF binary system. The sequence of stabilities of complexes in an AN-THF binary solution (mol. % AN = 75.0) at 25°C is [(DCH18C6)La)]³⁺ > [(DCH18C6)UO₂]²⁺ > [(DCH18C6)Ag]⁺ ∼ [(DCH18C6)NH₄]⁺, but in the case of other binary systems of AN/THF (mol. % AN = 25.0 and 50.0) is [(DCH18C6)La]⁺ > [(DCH18C6)NH₄]⁺ ∼ [DCH18C6)UO₂]²⁺ > [(DCH18C6)Ag]⁺. The text was submitted by the authors in English.     

Synthesis,crystal structure and properties of three ternary dysprosium 2-halogenated benzoic acid complexes

Three ternary dysprosium complexes [Dy(2-ClBA)₃?·?phen]₂ (1), [Dy(2-ClBA)₃?·?2,2′-bipy]₂ (2), and [Dy(2-BrBA)₃?·?phen]₂ (3) (where 2-ClBAH?=?2-ClC₆H₄COOH, 2-BrBAH?= 2-BrC₆H₄COOH, phen?=?1,10-phenanthroline, and 2,2′-bipy?=?2,2′-bipyridine) have been synthesized and characterized by X-ray single crystal diffraction. Complex 1 consists of two independent binuclear molecules, [Dy(2-ClBA)₃?·?phen]₂ (a) and [Dy(2-ClBA)₃?·?phen]₂ (b), in which the coordination environment is similar. Each Dy³⁺ is nine coordinate with two nitrogens from phen and seven oxygens from five 2-ClBA groups. 2-ClBA groups coordinate to Dy³⁺ in three ways, bidentate chelating, bidentate-bridging and terdentate-bridging. Complexes 2 and 3 consist of one binuclear molecule. The crystal structure of 2 is similar to that of binuclear molecule (a) or (b) of complex 1. In 3, each Dy³⁺ ion is eight-coordinate by two nitrogens from phen and six oxygens from five 2-BrBA groups. 2-BrBA groups coordinate to the Dy³⁺ ion in two ways, bidentate chelating and bidentate-bridging. The complexes were studied by UV, DTA-TG, and fluorescence spectrometry.     

Synthesis,crystal structure and properties of manganese(II) complexes with the tripod ligand tris(2-benzimidazylmethyl)amine and α,β-unsaturated carboxylates

Two new ternary complexes of manganese(II) with tris(2-benzimidazylmethyl)amine (ntb), and two different α,β-unsaturated carboxylates, {[Mn(ntb)(acrylate)](ClO₄)}₂?·?(H₂O)·3(CH₃OH) (1) and {[Mn(ntb)(α-methacrylate)](ClO₄)}₂·(H₂O)·2(CH₃OH) (2), have been synthesized and characterized by means of elemental analyses, thermal analyses, IR, UV and single crystal X-ray diffraction. In the two complexes, ntb functions as a tripodal tetradentate ligand, resulting in trigonal pyramidal geometry. In each complex, an additional ligand, acrylate anion, or α-methacrylate anion, is coordinated at the opened site trans to the apical nitrogen atom of the ntb ligand. The crystal structure of 1 shows two crystallographically independent but chemically identical [Mn(ntb)(acrylate)]⁺ cations. In 2, the crystal structure shows two crystallographically independent and chemically different [Mn(ntb)(a-methacrylate)]⁺ cations. Cyclic voltammograms of the manganese complexes indicate a quasireversible Mn³⁺/Mn²⁺ couple. The X-band EPR spectrum of the complexes exhibits a six-line manganese hyperfine pattern with g?=?2, A?=?97 (1) and 93?G (2). The spectrum confirms that the material is high-spin Mn(II).