Crystal structures, luminescent properties and thermal decomposition kinetics of some binuclear lanthanide complexes with 2,3-dichlorobenzoic acid anion and 2,2′-bipyridine

Some binuclear lanthanide complexes with the general formula [Ln(2,3-DClBA)₃bipy]₂ (Ln = Sm(1), Eu(2), Tb(3), Dy(4), and Ho(5); 2,3-DClBA = 2,3-dichlorobenzoate; bipy = 2,2′-bipyridine) were synthesized and characterized by elemental analysis, molar conductance, infrared, ultraviolet, luminescent spectroscopy, thermogravimetry, and different thermogravimetry (TG–DTG) techniques. The single crystals of the complexes have been obtained except the complex 2 and their structures have been determined by single-crystal X-ray diffraction. The four complexes are isostructural and the rare earth ions are all nine coordinated. The two rare earth ions in each complex are linked by two bridging bidentate and two chelating-bridging tridentate carboxylate groups. Under ultraviolet light excitation, the europium and terbium complexes exhibited characteristic red fluorescence of Eu³⁺ ion and green fluorescence of Tb³⁺ ion at room temperature. The non-isothermal kinetics was investigated by using the integral isoconversional non-linear (NL-INT) and the Popescu methods. The mechanism functions of the first decomposition step of the complexes 3–5 were determined. Meanwhile, the thermodynamic parameters (ΔG ^≠ , ΔH ^≠, and ΔS ^≠) at DTG peak temperatures were also calculated.     

Kinetics of the thermal decomposition of 2,2′-azobis(2-methylpropionamidine)dihydrochloride studied by the potentiometric method using metal complexes

A potentiometric method was proposed for the determination of rate constants for peroxyl radical generation using the reduced form of the metal in the complex. The kinetics of the thermal decomposition of 2,2′-azobis(2-methylpropionamidine)dihydrochloride was studied. The requirements for an electron donor (reactant) were formulated. The iron(ii) complex with EDTA, the iron(ii) complex with o-phenanthroline, and potassium hexacyanoferrate(ii) were used as reactants. The rate for peroxyl radical generation and the generation rate constant (the latter turned out to be (0.92±0.06)?10^–6 s^–1) were calculated. The studies were carried out for different temperatures and concentrations of the initiator and complex.     

Thermal decomposition and kinetics studies on the poly (2,2-dinitropropyl acrylate) and 2,2-dinitropropyl acrylate–2,2-dinitrobutyl acrylate copolymer

Journal of Thermal Analysis and Calorimetry - Thermal stability and decomposition kinetics of two energetic binders: poly (2,2-dinitropropyl acrylate) (PDNPA) and 2,2-dinitropropyl...     

Synthesis of Polyiodides of N- and S-S-Acetonyl Derivatives of 2,2′-(Disulfanediyl)- and 2,2′-[Alkanediylbis(sulfanyl)]-bisbenzimidazolium

Russian Journal of Organic Chemistry - 2,2′-(Disulfanediyl)- and 2,2′-[alkanediylbis(sulfanyl)]-bisbenzimidazoles react with aliphatic, aromatic, and heterocyclic α-iodoketones in...     

Characterization of pure phase Zn(II) oxide nanoparticles via thermal decomposition of two zinc(II) complexes of the 6,6′-dimethyl-2,2′-bipyridine ligand

Two zinc(II) complexes [Zn(6,6′-dimethyl-2,2′-bipy)Cl₂] _n (1) and [Zn(6,6′-dimethyl-2,2′-bipy)I₂] _n (2) are synthesized from the reaction of the 6,6′-dimethyl-2,2′-bipy ligand with ZnCl₂ and ZnI₂. Zinc(II) oxide nanoparticles are synthesized by the thermolysis of [Zn(6,6′-dimethyl-2,2′-bipy)Cl₂] _n (1) and [Zn(6,6′-dimethyl-2,2′-bipy)I₂] _n (2) at two different temperatures. The ZnO nanoparticles are characterized by X-ray diffraction and scanning electron microscopy (SEM). SEM images show the average size of the ZnO nanoparticles produced of 50 nm and 60 nm in compounds 1 and 2 respectively.     

Evaluation on thermal stability and kinetics of 2,2′-azobis(2,4-dimethyl)valeronitrile in aerobic and anaerobic conditions under isothermal process

Journal of Thermal Analysis and Calorimetry - We quantified the thermal stability of 2,2′-azobis(2,4-dimethyl)valeronitrile (ADVN) under isothermal conditions through thermogravimetry (TG),...     

Supramolecular structures,thermal decomposition mechanism and heat capacity of the novel binuclear Tb(III) and Dy(III) complexes with 2,3-dimethoxybenzoic acid and 5,5′-dimety-2,2′-bipyridine

Journal of Thermal Analysis and Calorimetry - Two novel binuclear lanthanide complexes [Tb(2,3-DMOBA)3(5,5′-DM-2,2′-bipy)]2·C2H5OH (1) and...     

Studies on the non-isothermal kinetics of the thermal decomposition of [Cu(NBOCTB)][Cu(NO3)4]· H2O

The thermal decomposition process of the complex [Cu(NBOCTB)][Cu(NO₃)₄] H₂O has been studied by TG and DTG technique, and possible intermediates of the thermal decomposition have also been conjectured from the TG and DTG curves. The results suggest that the decomposition of the complex involves five steps: The non-isothermal kinetics of steps 1, 2 and 3 have been studied by means of the Achar and Coats-Redfern method based on TG and DTG curves. Step 1 is a Coring and Growth mechanism (n= 1), its kinetic equation may be expressed as: d/dt=Ae^–E/RT(1–). Steps 2 and 3 are both two order chemical reaction mechanisms, their kinetic equations can be expressed as: d/dt=Ae^–E/RT(1–)².This project was supported by the National Natural Science Youth Fundation of China.     

Spectrophotometric and thermal lens determination of aluminum with 3-sulfo-5-nitro-4′-diethylamino-2,2′-dihydroxyazobenzene

The conditions of the spectrophotometric and thermal lens determination of aluminum with sulfo-5-nitro-4′-diethylamino-2,2′-dihydroxyazobenzene have been compared. The limit of spectrophotometric detection of aluminum in aqueous solutions has been found to be 8 ng/mL. On the basis of the conditions of spectrophotometric determination, the conditions for thermal lens determination have been proposed (532.0 nm, exciting radiation power of 42 mW); they provide a decrease of the detection limit down to 0.6 ng/mL and an increase of the sensitivity coefficient by an order of magnitude. It has been shown that, in the case of the thermal lens determination of aluminum in water-organic mixtures (50 vol % of dimethyl sulfoxide or 30 vol % acetonitrile), the sensitivity coefficient is respectively 9.1 and 6.3-fold higher as compared with the thermal lens determination in water. As a result, the detection limits are reduced 2.5 and 10-fold, respectively. Aluminum has been determined by thermal lens spectrophotometry in Moscow’s tap water using the standard addition method, its concentration being 0.79 ± 0.07 mg/L, which is above the threshold limit value of the aluminum content of drinking water.     

Synthesis and Properties of Polyamides of 2,2′-[Isopropylidenebis-(p-phenyleneoxy)] diacetic Acid

A group of six semiaromatic polyamides of 2,2′-[isopropylidenebis-(p-phenyleneoxy)]diacetic acid (Bisacid A₂) were synthesized by low-temperature solution polycondensation techniques. Six different diamines were condensed independently with Bisacid A₂ chloride in a mixture of N-methylpyrrolidone (NMP and hexamethylhosphoramide (HMPA). The polymers were obtained in 82–95% yield and possessed inherent viscosities in the range from 0.32 to 0.63 dL/g. The polyamides were characterized by IR and 'H-NMR spectra. The molecular weight and molecular weight distribution of the polyamides were determined by gel-permeation chromatography. The thermal stability, thermal degradation kinetics, crystallinity, density, and solubility were also determined. A model diamide (MDA) was synthesized from aniline and Bisacid A₂ chloride to confirm the formation of polyamides from diamines.     

Preparation of LiZnPO4·H2O via a novel modified method and its non-isothermal kinetics and thermodynamics of thermal decomposition

The single phase ??-LiZnPO₄·H₂O was directly synthesized via solid-state reaction at room temperature using LiH₂PO₄·H₂O, ZnSO₄·7H₂O, and Na₂CO₃ as raw materials. XRD analysis showed that ??-LiZnPO₄·H₂O was a compound with orthorhombic structure. The thermal process of ??-LiZnPO₄·H₂O experienced two steps, which involved the dehydration of one crystal water molecule at first, and then the crystallization of LiZnPO₄. The DTA curve had the one endothermic peak and one exothermic peak, respectively, corresponding to dehydration of ??-LiZnPO₄·H₂O and crystallization of LiZnPO₄. Based on the iterative iso-conversional procedure, the average values of the activation energies associated with the thermal dehydration of ??-LiZnPO₄·H₂O, was determined to be 86.59?kJ?mol^?1. Dehydration of the crystal water molecule of ??-LiZnPO₄·H₂O is single-step reaction mechanism. A method of multiple rate iso-temperature was used to define the most probable mechanism g(??) of the dehydration step. The dehydration step is contracting cylinder model (g(??)?=?1?(1???)^1/2) and is controlled by phase boundary reaction mechanism. The pre-exponential factor A was obtained on the basis of E _a and g(??). Besides, the thermodynamic parameters (??S ^??, ??H ^??, and ??G ^??) of the dehydration reaction of ??-LiZnPO₄·H₂O were determined.     

Synthesis and characterization of complexes of the first transition series cations with 2,2′-biimidazole and 2,2′-biimidazolate

Mononuclear [M(hfacac)₂(H₂biim)] complexes, where M = Mn^II, Fe^II, Co^II, Ni^II, Cu^II or Zn^II, hfacac = hexafluoroacetylacetonate, H₂biim = 2,2-biimidazole; dinuclear K₂[M₂(acac)₄(-biim)] (M = Cu^II or Zn^II) and tetranuclear K₂[M₄(acac)₈( ₄-biim)] (M = Co^II or Ni^II) complexes have been prepared and characterized by chemical analysis, conductance measurements, i.r., electronic and e.p.r. spectroscopies and by magnetic susceptibility measurements (in the 2–300 K range). Mn^II, Fe^II and Co^II are in a high spin state. The e.p.r. spectra of Cu^II and Mn^II compounds have been recorded.     

Thermal decomposition and thermal stability of potassium 3,3′-dinitrimino-5,5′-bis(1H-1,2,4-triazole)

Journal of Thermal Analysis and Calorimetry - Potassium 3,3′-dinitrimino-5,5′-bis(1H-1,2,4-triazole) (K2DNABT), a new potential green primary explosive, was synthesized and...     

Can Na(2)[B(12)H(12)] be a decomposition product of NaBH(4)?

We synthesized Na(2)[B(12)H(12)] by a solid state procedure and thermal decomposition of Na[B(3)H(8)], and calculated from a first-principles approach the thermodynamic and structural properties. In particular, the calculated enthalpy of formation of the monoclinic structure, at T = 0 K, of -1086.196 kJ mol(-1) showed that it is a very stable compound. Therefore, in case it were formed during the thermal decomposition of NaBH(4), it would be rather considered a product, which, in addition, prevents the subsequent re-hydrogenation process because of its low reactivity to hydrogen. We reported the isotherms of absorption of H(2), O(2), and H(2)O, calculated both theoretically and experimentally.     

Effect of some added salts on the kinetics of dissociation of tris-2,2′-bipyridine-Fe(II) complex

Both monovalent cations and anions show a regular gradation, according to their sizes, in their effect on the rate and the activation parameters for the dissociation of tris(2,2′-bipyridine)-Fe(II) complex in acid. ΔS and ΔH of activation in M, 0.1 M and 0.01 M acid decrease in the order Cl⁻ > Br⁻ > I⁻ for anions and Li⁺ > Na⁺ > Cs⁺ for cations. The effect of the bulky tetra-alkyl ammonium ions is anomalous and does not depend on their sizes. The effect of the anions can be rationalized in terms of their involvement with the vacant coordination site of the partially bonded intermediate. The effect of cations is probably due to their altering the water structure at high concentration. The anomalous of the tetra-alkyl ammonium ions supports this view.     

Role of anions in the kinetics of the acid catalyzed dissociation of tris-(2,2′bipyridine) Fe(II) complex

Excess of Cl⁻ and NO₃⁻ ions bring about a significant increase in the rate of dissociation of the tris-(2,2′bipyridine) Fe(II) complex in HCl, HClO₄ and H₂SO₄ in a very narrow range of H⁺ concentration (∼0·1−0·3 M). Above and below this concentration range, these anions do not lead to significant variation in the rate of dissociation. This points to the involvement of these ions in a kinetic step which is only important in the rate expression in this narrow range. It is suggested that the anions occupy the coordination site left vacant by the partial dissociation of the complex leading to the half bonded intermediate. This would significantly lower the free energy of activation for the subsequent protonation step leading to complete dissociation and thus lead to acceleration. The lowering of the free energy of activation will be mainly due to an increase in entropy of this intermediate on account of charge reduction and lower rigidity due to lack of hydrogen bonding. The retarding effect of SO₄²⁻ concentrations and the unambiguously interpreted as its addition leads to simultaneous changes in H⁺ and HSO₄⁻ concentrations and the possibility of ion pair formation with the complex cannot be ruled out.     

Effect of solvent on the crystal structures of copper(II) complexes based on 4′-(4-methoxyphenyl)-2,2′:6′,2″-terpyridine and 4′-(3-chlorophenyl)-2,2′:6′,2″-terpyridine

Four homoleptic copper(II) complexes, [Cu(Meophtpy)₂](ClO₄)₂ (Meophtpy = 4′-(4-methoxylphenyl)- 2,2′:6′,2″-terpyridine) (I), [Cu(Meophtpy)₂](ClO₄)₂ · 2H₂O (II), [Cu₂(m-Clphtpy)₄](ClO₄)₄ (m-ClPhtpy = 4′-(3-chlorophenyl)-2,2′:6′,2″-terpyridine) (III), and [Cu₂(m-ClPhtpy)₄](ClO₄)₄ (IV) have been synthesized by hydrothermal methods and characterized by IR, elemental analysis and single crystal X-ray diffraction (CIF files CCDC nos. 963375 (I), 885457 (II), 963377 (III), and 963376 (IV)). Complex II is a polymorph of I and complex IV is a polymorph of III. All these complexes are obtained with 95% ethanol solution or 50% ethanol solution and the solvent control on the crystallization are obviously found. In all complexes, the face-to-face interactions between pyridyl rings or phenyl rings facilitate the construction of 3D network in the crystal in addition to hydrogen bonds. The fluorescence properties of these complexes have been investigated.     

2,2′-carbonyl-bis(3,5-dioxo-4-methyl-1,2,4-oxadiazolidine): II-reagent for the direct esterification of carboxylic acids.

Reaction of carboxylic acids including N-protected α-amino acids with 2,2′-carbonyl bis(3,5-dioxo-4-methyl-1,2,4-oxadiazolidine) and alcohols affords the corresponding esters under mild conditions.