The pKa values of N,N,N',N'-tetrakis-(2-hydroxypropyl)ethylenediamine

Aqueous solutions of the industrially important chelating agent N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine exhibit basic properties. The proton dissociation constants were determined to be 8.99 ± 0.04 (pK₁) and 4.30 ± 0.04 (pK₂) by potentiometric titration at 25° in 0.15M sodium chloride.     

A convenient synthesis of N,N',N''-trisubstituted diethylenetriamines

N,N',N''-Trisubstituted diethylenetriamines (1,4,7-triaza-heptanes) were synthesized by reduction of the relevantly substituted 2,2'-iminodiacetiamides which, in turn, were accessed from cheap reactants by the methods depending on their nature. The triamines thus obtained may be promising ligands for metal catalysts.     

Novel coupling reaction between sulfonyl azide and N,N,N',N'-tetramethylthiourea

The synthesis of sulfonylguanidines from N,N,N',N'-tetramethylthiourea and sulfonyl azides is described. This method serves as an alternative route for generating sulfonylguanidines via the use of stable starting materials.     

Synthesis and electrochemical and spectroscopic studies of a N,N,N',N'-tetraphenylbenzidine-bridged bis(2,2'-bipyridine) ligand and diruthenium complex

A N,N,N',N'-tetraphenylbenzidine-bridged bis(2,2'-bipyridine) ligand and corresponding diruthenium complexes were synthesized and characterized. They show rich multistep redox processes due to the stepwise oxidations of the amine units and ruthenium components. Their absorption and emission spectral changes in response to electrochemical stimulus were examined by spectroelectrochemical measurements. DFT and TDDFT calculations were performed to complement the experimental results.     

N,N'-diarylformamidinato complexes of the platinum group metals

Some platinum group metal hydrides react with N,N'-diarylcarbodiimides in boiling toluene to yield products containing novel bidentate N,N'-diarylformamidinate (ArNCHNAr) ligands.     

N-Isopropyl-N',N'-diphenyl-N-(silylmethyl)ureas: Synthesis and structure

New N-isopropyl-N',N'-diphenyl-N-(silylmethyl)ureas were obtained, and their structure was explored by ¹H, ¹³C, ²⁹Si NMR spectroscopy and X-ray analysis. These results have shown that N-isopropyl-N', N'-diphenyl-N-[(fluorosilyl)-methyl]ureas exist as (O–Si) chelates with intramolecular dative bond C=O→Si.     

Bis(furazano)pyridinone N,N'-dioxide: a new high-density insensitive explosive

The synthesis and properties of novel high-dense energetic material based on new 4H,8H-bis(furazano)[3,4-b:3',4'-e]-pyridine ring system are described. An operationally simple, efficient and scalable protocol towards 4H,8H-bis(furazano)-[3,4-b:3',4'-e]pyridin-8-one 1,7-dioxide from commercially available 4-amino-2,6-dichloropyridine in three steps, namely, nitration–azidation–cascade ring closure, has been developed.     

Aluminum(III) di- and monochlorides incorporating an N,N'-chelating iminophosphonamide ligand: synthesis and structures

Treatment of lithium iminophosphonamide with AlCl₃ in Et₂O led to the formation of an aluminum(III) dichloride complex as colorless crystals. The substitution reactions of aluminum(III) dichloride stabilized by an iminophosphon- amide ligand with N- and Fe-nucleophiles gave the corresponding compounds of aluminum(III) monochloride. The reaction of the aluminum(III) dichloride complex with CpNa proceeded slowly at room temperature to form an aluminum(III) monochloride complex bearing an η¹(σ)-bonded cyclopentadienyl ring.     

Molecular diversity of triphenylphosphine promoted reaction of electron-deficient alkynes and arylidene Meldrum acid (N,N'-dimethylbarbituric acid)

The three-component reaction of triphenylphosphine, dimethyl hex-2-en-4-ynedioate and arylidene N,N'-dimethylbarbituric acids in dry methylene dichloride at room temperature afforded trans-1,3-disubstituted 7,9-diazaspiro[4.5]dec-1-enes in good yields and with high diastereoselectivity. However, the similar three-component reaction with arylidene Meldrum acids resulted in a mixtures of cis/trans-1,2-disubstituted 7,9-dioxaspiro[4.5]dec-1-enes. Additionally, the three-component reaction of triphenylphosphine, dimethyl but-2-ynedioate and arylidene Meldrum acids gave polysubstituted 5-(triphenyl-λ⁵-phosphanylidene)cyclopenta-1,3-dienes. A plausible reaction mechanism was proposed for the formation of various products with different regioselectivity and diastereoselectivity.     

The effect of halloysite nanotubes and N,N'- ethylenebis (stearamide) on the properties of polylactide nanocomposites with amorphous matrix

Amorphous polylactide/halloysite nanotube (PLA/HNT) nanocomposites were prepared and examined. Neat HNT and HNT treated with N,N'- ethylenebis(stearamide) (EBS) were used as nanofillers. The role of HNT and/or EBS content on the cold crystallization of amorphous PLA matrix, HNT dispersion, as well as on the dynamic mechanical and optical properties of the materials was determined.The PLA/HNT-based nanocomposites contained well-distributed nanotubes and occasionally micron-sized aggregates, especially at high loading. HNT, EBS treated HNT and EBS influenced the cold crystallization of PLA, therefore the formation of the disorder α′ and the order α crystallographic forms of PLA.The nanocomposites exhibited increased stiffness and decreased transparency compared to the neat PLA. Due to the reinforcing effect and additional specific features of HNT, the addition of the nanofiller allows tuning of the properties of the nanocomposites with amorphous PLA matrix.     

Metal chelates of phosphonate-containing ligands-I Stability of some N,N,N',N'-ethylenediaminetetra(methylenephosphonic) acid metal chelates

A potentiometric investigation of the acid dissociation constants of the octabasic ENTMP [N,N,N',N'-ethylenediaminetetra(methylenephosphonic) acid] is reported. The stability constants of protonated MH(n)L (n = 1, 2, 3 and 4) and unprotonated ML metal chelates of Mg, Ca, Ba and Cd with ENTMP have been measured. The stabilities are in the order Mg < Ca < Ba < Cd.     

Metal complexes of 1,4,10-trioxa-7,13 -diazacyclopentadecane-N,N&#x27;-diacetic acid

The cyclic diaza-crown ether complexone cTOPDA (1,4,10-trioxa-7,13-diaza- cyclopentadecane-N,N'-diacetic acid) has been synthesized and characterized by elemental analysis, titration and NMR spectroscopy. Its ionization constants and the stability constants of its ML and M₂L complexes formed with alkali, alkaline-earth and some transition and representative metals were determined at 25.0±0.1°C and ionic strength 0.10 M (Me₄NNO₃). This ligand forms considerably more stable complexes with the transition metals than the analogous tetraoxa-diaza crown ether complexone cTOODA (1,4,10,13- tetraoxa-7,16-diazacyclooctadecane-N,N'-diacetic acid), but this last ligand favours ions with larger size, particularly K⁺. The cobalt(II) complex of cTOPDA is more stable than the nickel(II) complex, hence the Irving-Williams' order of stability is not obeyed for its transition-metal complexes. These effects are discussed in terms of the size of the cavity of the ligand and of the stereochemical constraints that it may impose.     

The crystal structure of (phenylazophenyl-C,N&#x27;)mercury(II) chloride: a dimeric rans-metallation reagent

An X-ray diffraction study of (phenylazophenyl-C,N')mercury(II) chloride has shown it to be dimeric via long HgCl bridging interactions of 3.367 Å.     

Metal chelates of phosphonate-containing ligands-IV (Stability of some 1,6-hexamethylenediamine-N,N,N',N'-tetra(methylenephosphonic) acid metal chelates)

The stability constants of the complexes formed between the anion of 1,6-hexamethylenediamine-N,N,N',N'-tetra(methylenephosphonic) acid and some transition and non-transition metal ions have been measured potentiometrically at a temperature of 25 degrees and an ionic strength of 0.1M (KNO(3)). The acid dissociation constants of the ligand and stability constants of the protonated complexes are also reported. Comparisons are made with the acid dissociation constants of the analogous compounds EDTA, ENTMP and HDTA, and possible structural formulae are given.     

1D CuI coordination polymers based on triphenylarsine and N,N&#x27;-ditopic co-ligands: synthesis,crystal structure and TADF properties

1D coordination polymers [Cu₂I₂(AsPh₃)₂(L)]_n (L = 4,4'-bi-pyridine, pyrazine) were synthesized via the reaction of CuI with AsPh₃ and N,N'-ditopic co-ligand s L. At ambient temperature, these polymers exhibit short-lived (2.3–3.2 μs) thermally activated delayed fluorescence (TADF) with _max at 530 nm (L = 4,4'-bipyridine) and 605 nm (L = pyrazine) and quantum efficiency up to 45%.     

Gamma-irradiation effects on the electrical conductivity of pure and Cu-doped Fe3O4 spinel

The electrical conductivity and IR-spectra of pure and Cu-doped Fe₃O₄ spinels were measured at 300–1000 K. Two breaks in the conductivity-temperature curves have been observed for all investigated pure and doped samples. One of these two breaks were found near the Curie point of the investigated spinel. The electrical conduction in -irradiated and non-irradiated pure and Cu-doped Fe₃O₄ occurred by a hopping mechanism due to a fast electron exchange between Fe²⁺ and Fe³⁺-ions present on octahedral sites. The Seebeck-voltage of the irradiated and non-irradiated pure and Cu-doped samples has been measured. The effect of -irradiation on the conductivity values //, activation energy and type of defects was discussed.     

Mixed ligand complexes in vinyl polymerization. I. [N,N′-ethylenebis (salicylideneiminato)](acetylacetonato)cobalt(III) as an initiator

Polymerization of methyl methacrylate in the presence of a mixed ligand complex, [N,N′-ethylenebis(salicylideneiminato)](acetylacetonato)cobalt(III) in benzene was studied. The rate of polymerization was proportional to the square root of the concentration of the chelate and the monomer exponent was 1.67 and 1.69 at 60 and 70°C, respectively. The activation energy and the kinetic and transfer constants were evaluated. A free-radical mechanism has been proposed.     

Substituent effects on the stability of copper(II) chelates with some Neville Winter's azo dyes

The effect of substituents on the stability of the complexes formed by reaction of Neville Winter's acid para-substituted azo dyes (p-chloro, methoxy, nitro, and sulfonic) is studied. Log K values for the complexes were determined spectrophotometrically. The p-methoxy and p-chloro chelates exhibited maximum and minimum stabilities, respectively, the methoxy group being electron repelling and chlorine electron withdrawing. Calculations applying Hammett and linear free energy equations indicate that copper in these chelates acts as a π-electron accepter and that such chelates exhibit coplanarity.     

Gamma-irradiation effects on the electrical conductivity of pure and Co-doped MgAl2O4 spinel

The electrical conductivity of pure and Co-doped MgAl₂O₄ spinels was measured at 700–1100 K. The results of both pure and doped spinels were found to be fitted with an exponential expression with two different activation-energy parameters, in two ranges of temperature. The effect of -irradiation on the electrical conductivity of pure and doped spinels was also studied. The kinetic parameters of the isothermal annealing of the induced irradiation damages in the spinels were determined. All the results were found to be consistent with the ionic conduction which was suggested to be due to the motion of the cation vacancy.