Neue Tetrathiocyanato-diamin-Chromiate mit aliphatischen Monoaminen

New Tetrathiocyanato-diamine-chromiates with Aliphatic Monoamines Two new Reinecke salt like compounds were obtained by a substitution reaction of anhydrous K₃[Cr(NCS)₆] with aliphatic monoamines (n-propylamine and n-butylamine) in the molten state. The formulae of the [Cr(CNS)₄(n-propylamine)₂]^? and [Cr(NCS)₄(n-butylamine)₂]^? were proved by a series of double decomposition reactions with the hydrochlorides of heterocyclic N-bases and alkaloids and with cobalt(III)-amine bases, respectively. From spectroscopical investigations (u.v. and i.r.) some structural problems are resolved and discussed.     

Fluorescent macrocyclic chemosensor for Zn(II) detection at alkaline pH values

ABSTRACT

The new macrocyclic ligand L (28,29-dimethoxy-27-oxa-8,11,14,17,25,26-hexaazatetracyclo[22.2.1.1(2,6).1(19,23)]nonacosa-2,4,6(28),19,21,23(29),24,26(1)-octaene) has been synthesised. It contains a tetramine chain and the 2,5-bis(2-methoxy-3-metyl-phenyl)-1,3,4-oxadiazole (PPD-OMe) chromophore, acting as coordinating and sensing units, respectively.

The fluorescent emission of L depends on the pH being highly fluorescent at pH = 2 and not emitting from pH >10. The studies highlighted that L is a PET mediated emitting chemosensor, being the PET effect regulated by the degree of the tetraamine protonation.

L coordinates metal ions (Cu(II), Zn(II) and Cd(II)) in water giving rise to an OFF-ON fluorescent response for the presence of Zn(II) ion thus signalling its presence in the medium. This response is particularly notable at pH = 9 allowing to extend the Zn(II) sensing also in the alkaline pH field.     

Strong binding between acidic guests and fluorescein modified -γ-Cyclodextrin via hydrogen bonding

-Cyclodextrin with appended fluorescein (1) has been prepared as a sensor and a charge-changeable receptor for detecting organic compounds including terpenoids, carboxylic acids and bile acids. Compound1 has cationic, neutral and anionic forms depending on the pH of the solutions. The anionic form of1 at about neutral pH exhibits the highest sensing ability for carboxylic acids and bile acids, while at alkaline pH it detects hardly any of the guests examined. The high sensitivity and selectivity of the anionic form of1 at around neutral pH for acidic guests seems to be caused by the hydrogen bond between the phenoxide anion moiety of fluorescein and acidic guests. The neutral form of1 exhibits little sensing ability for all the guests, but the cationic form shows comparatively higher sensing ability for the guests examined.     

A new procedure for determining copper in igneous rock and alloys

The influence of cationic surfactants, cetylpyridinium chloride (CPC), cetylpyridinium bromide (CPB), and cetyltrimethylammonium bromide (CTMAB), on the complexation of copper(II) with thenoyl-(2-oxopropyl)-N-(2-sulfo-4-nitro-5-oxyphenyl) azomethine (R) has been investigated. It has been found that monoligand compounds are formed at pH 4, while at pH 3 the formation of mixed-ligand compounds is observed. The detection limit for copper decreases and the stability constants of the complexes increase in the row Cu-R-CPC > Cu-R-CPB > Cu-R-CTMAB, with AN increase in the stability of the associates (Rh-CPC > R-CPB > R-CTMAB) in the complexation reaction. The ratio of components in monoligand (1: 1) and mixed-ligand (1: 1: 1) compounds has been determined. The limits of obedience to the Beer law have been found. A procedure has been developed for the photometric determination of copper in igneous rock and alloys.     

pH-dependent Co(II) assemblies from achiral 2-benzothiazolylthioacetic acid: crystal structures,symmetry breaking,and magnetic properties

Based on an achiral 2-benzothiazolylthioacetic acid (HL) ligand, three Co(II) coordination compounds, {[Co(L)₂(H₂O)₃]·H₂O}_n (1), [Co(L)₂(H₂O)₂]_n (2), and [Co(L)₂(H₂O)₄]·2H₂O (3), were obtained under different pH environments. Compound 1 possessing an interesting chiral 1-D helical double chain was synthesized with pH of 5.0~6.5, and the chiral symmetry breaking has been probed by single-crystal X-ray diffraction and circular dichroism spectroscopy. Switching pH to 4.0~5.0 and 3.0~4.0 resulted in achiral 2 and 3, respectively. Compound 2 has a 1-D chain structure and 3 is mononuclear.     

Selective separation of yttrium(III) through a liquid membrane system using 2-thenoyltrifluoroacetone as an extractant carrier

2-Thenoyltrifluoroacetone has been offered as a mobile carrier in organic phase for the transport and selective separation of yttrium from aqueous media using a liquid membrane system. Perceivably, the use of n-propylamine (PA) in the source phase enhances the transport of yttrium ions. The extraction and stripping conditions have entirely been evaluated and explained. The suggested method has been utilized for the separation of yttrium(III) from its binary mixtures with strontium(II) and some other cations such as Ni²⁺, Co²⁺, Ag⁺, Fe²⁺, Al³⁺, Cu²⁺, Hg²⁺and Cs⁺ in aqueous solutions of pH 5.4 in the presence of PA, while 1 M nitric acid was acting as a stripping agent in the receiving division. Cyanide ion and 5-sulfosalicylic acid have been used as masking agents to minimize the interferences from different transition metal ions and Al³⁺ in the source phase, respectively. ⁹⁰Y in secular equilibrium with ⁹⁰Sr in the source phase, was transferred to receiving phase and separated completely from its long-lived parent isotope. The activity of the transported ⁹⁰Y was found to decay with a half-life 64.17 ± 0.05 h. The purity of yttrium-90 was comparable or better than the other applied liquid membrane systems for purification of yttrium-90.     

pH-Responsive Phase Transition of Supramolecular Hydrogel Consisting of Glycosylated Amino Acetate and Carboxylic Acid Derivative

By addition of a carboxylated amino acetate (2) to a low-molecular-weight hydrogel (1) which has a unique thermally induced volume-phase transition character, a macroscopic pH-responsive feature is newly conferred on the supramolecular hydrogel. The direct observation of temperature-dependent behavior of the mixed hydrogel clearly showed that the thermally induced swelling-shrinkage type of the volume phase transition at pH 4 is shifted to the gel–sol transition at pH 7 by 10?mol% addition of 2 to the hydrogel 1. On the basis of the measurements by TEM, SEM, XRD and FT-IR, it is conceivable that incorporation of the anionic carboxylate of 2 slightly disturbs the packing of the hydrogen bond belt of the mixed hydrogel. Such a slight disturbance greatly leads to the sol–gel transition by elevating temperature, instead of the volume-phase transition. Introduction of dynamic characteristics to supramolecular systems in a macroscopic level may extend the potential of these materials in various fields.     

The Synthesis and Antimicrobial Screening of Some Novel AZA-Imidoxy Compounds as Potential Chemotherapeutic Agents

Some novel azaimidoxy compounds viz. 2-{[(4-chlorophenyl)diazenyl]oxy}-1H-isoindole-1,3-(2H)-dione (Va), and 1-{[1-naphthyldiazenyl]oxy}pyrrolidine-2,5-dione (IVc), etc. have been synthesized by a simple diazotization reaction followed by a coupling with 2-hydroxy-1H-isoindole-1,3(2H)-dione (III)/1-hydroxypyrrolidine-2,5-dione (II) of corresponding aromatic primary amine derivatives at a suitable pH. A similar reaction with a [1,3]thiazolo[4,5-b]pyridin-2-amine (VIII) lead us to some interesting results variable with a pH. The structure of all synthesized compounds has been established by IR, ¹H NMR, and mass studies. These compounds have been screened for antimicrobial activities in order to evaluate the possibility of the derivatives to be used as potential chemotherapeutic agents.     

Supramolecular nanoscale systems based on amphiphilic tetramethylensulfonatocalix[4]resorcinarenes and cationic polyelectrolyte with controlled guest molecule binding

The water-soluble tetramethylensulfonatocalix[4]resorcinarene with methyl (C1) and pentyl (C5) substitutes on the lower rim forms colloid nanoscale aggregates with poly(diallyldimethylammonium chloride) (PDDA) in aqueous solutions. The size and stability of nanoparticles depend on concentrations of the components and their ratio in the ‘calixarene-polymer’ system. Ternary supramolecular complexes «polymer–macrocycle–guest molecule L-tryptophan (Trp) in conditions of spontaneous pH (3.80 and 4.78 for C1-PDDA and C5-PDDA systems, respectively) in an aqueous solution and in phosphate buffer (pH 7) were investigated by fluorescence method. The addition of the third component – PDDA – to the «non-aggregated C1–Trp» associates leads to the release of Trp in all studied conditions. The possibility of the «binding–release» process of L-tryptophan in «C5–Trp» associates after PDDA addition in the ternary complex is achieved and controlled by the structure of the macrocyclic self-associates and pH conditions.     

Solution structure and equilibrium of new calix[4]resorcinarene complexes—prototype of molecular machines. NMR data

Association properties and molecular machine application of water soluble calix[4]resorcinarene (1) with two aromatic guests (2-naphthol (2) and 1,5-naphthalenediamine (3)) have been investigated by various NMR methods (chemical shift, nOe and diffusion measurements) in aqueous solution at different concentrations and pH range. In neutral solution 1 strongly associates with 2, while only moderately associating with 3. Increase in concentration causes an increase in the stability of 1 + 3 and 1 + 2 + 3 complexes and produces high order complexes. The decrease of pH does not have an influence on 1 + 2 association, but disrupts 1 + 3 assembly. 1 can be used for the separation of 2 + 3 mixture in aqueous solution at moderate concentrations. The pH dependency of the association properties of the 1 + 3 system makes these compounds prime candidates for pH-responsive molecular machines applications.     

THE STRUCTURE OF myo-INOSITOL HEXAPHOSPHATE IN SOLUTION: 31P N.M.R. INVESTIGATION

Abstract

Changes in the ³¹P n.m.r. spectrum of myo-inositol hexaphosphate at different pH reveal that the conformation of this molecule varies with its degree of protonation. Above pH 12 it has the equatorial structure (Ie), below it has the axial conformation (Ia) which it retains to pH 5 when it reverts to le on the addition of a seventh proton. These changes are explained by strong hydrogen bonding between phosphate groups. There is also evidence that at low pH (2) the molecule again reverts to la.     

Fluorescent pH Indicator. Spectral Changes of 4-Methylumbelliferone

Abstract

4-Methylumbelliferone is a useful acid-base fluorescent indicator with a midpoint of its transition interval at pH 7.6. Both anionic and neutral forms fluoresce in the blue with high quantum yield (70%). The indicator properties are based on a blue shift of the absorption spectrum in acid. Depending on the excitation wavelength employed, one has the option of following either an increase or a decrease in fluorescence as the pH changes.     

Solution Phase Chemistry of Lanthanide Complexes. 12. 1:1 and 1:2 Lanthanide Complexes with s-Carboxymethoxysuccinic Acid

Abstract

The solution phase coordination chemistry associated with 1:1 and 1:2 complexes of lanthanide ions with S-carboxymethoxysuccinic acid (CMOS) has been studied by spectroscopic means. The Tb(III) luminescence intensities and lifetimes were found to be sensitive towards the solution phase properties, as were the circularly polarized luminescence spectra of these complexes. It was found that below pH 6, Ln(CMOS) complexes were monomeric in nature and contained an average of 6 molecules of coordinated water. Above neutral pH, the Ln(CMOS)₂ complexes became self-associated into hydroxy-bridged, oligomeric species. The Ln(CMOS)₂ complexes were found to be oligomeric at all pH values, with ligand bridging taking place below neutral pH and hydroxy bridging taking place above neutral pH.     

OXYDATION ALCALINE PAR L'ACIDE PERPROPIONIQUE D'ARYL MÉTHYL SULFURES EN SULFOXYDES. ETUDES EXPÉRIMENTALES ET THÉORIQUES DE L'OXYDATION NUCLÉOPHILE DE DÉRIVÉS P-SUBSTITUÉS DU THIOANISOLE PAR L'ANION PERPROPIONATE EN MILIEU MICELLAIRE

L'action de l'acide perpropionique CH₃CH₂CO₃H (1) a été étudiée en milieu alcalin micellaire (pH ～ 11; chlorure de cétyl triméthyl ammonium, CTACl) sur le thioanisole (4) et sur ses dérivés p-substitués, le p-méthoxy (2), le p-méthyl (3), le p-bromo (5) et le p-nitro (6). L'oxydation conduit exclusivement aux dérivés sulfoxydes (2a–6a). Les effets du pH, de la substitution et de la température ont permis de mieux comprendre la réaction d'oxydation de ces sulfures en sulfoxydes par l'acide perpropionique. Des calculs ab initio ont montré la cohérence de nos hypothèses. Enfin l'influence du milieu sur la cinétique de la réaction a été évalué en phase aqueuse (pH ～ 11) en présence de CTACl.

The reaction of perpropionic acid CH₃CH₂CO₃H (1) with thioanisole (4) and p-substituted thioanisoles [p-methoxy (2), p-methyl (3), p-bromo (5), and p-nitro (6)] in stoechiometric proportion has been carried out in micellar medium (cetyl trimethyl ammonium chloride, CTACl). Studies of the influence of the pH, the temperature and the substitution of the thioanisole, provide a better understanding of the sulfoxides (2a–6a) formation. Ab initio calculations have been achieved and the oxidation reaction has been studied in detail in aqueous medium (pH = 11).     

Examination of the Higuchi Model for the Release of Vitamin B2 from Multilayered Calcium Alginate/Chitosan Beads in Varying pH Medium

The release of model drug vitamin B₂ from calcium alginate/chitosan multi‐layered beads has been studied in the media of varying pH (3 h in the medium of pH 1.0 and for the remaining time in pH 7.4) at 37°C. The quantitative deviation of experimental data from the Higuchi model has been interpretated by using a newly developed ‘curve area measurement’ (CAM) approach. The higher deviation in the initial phase has been explained on the basis of porous structure of beads due to the use of low molecular weight polymers in the preparation of beads.     

Flow Injection Manifold for Simultaneous Spectrophotometric Determination of Bi (III), Pb (II)

Abstract

A FIA assembly producing a carrier with pH which can be adjusted to the desired pH value is propposed. It is based on the merging of two different solutions, one of them at constant flow-rate and the other at variable flow-rate. This manifold has been used for the simultaneous determination of Bi(III) and Pb(II) with Arsenazo III. Calibration curves are linear in the 1.0-11.0 ppm Bi (III) range at pH 0.25 and 1.0-12.1 ppm Pb (II) at pH 2.15. The effect of foreign ions is also reported.     

pH-Controlled syntheses of two hybrids based on octamolybdate and enrofloxacin

Two new drug molecules modifying octamolybdate-based hybrid compounds, H₂[Ni(L)₂(H₂O)₂]?·?(β-Mo₈O₂₆)?·?H₂O (1) and [Ni₂L₂(H₂O)₄(α-Mo₈O₂₆)] (2) (L?=?enrofloxacin), have been synthesized at different pH values under hydrothermal conditions. Compound 1 was synthesized at pH?≈?5, in which the octamolybdate shows β-isomer and the isolated Ni-enrofloxacin coordination subunits array on both sides of β-Mo₈O₂₆. Compound 2 was synthesized at pH?≈?4, with octamolybdate showing the α-isomer and Ni-enrofloxacin having 1-D chain structure along the a-axis with α-Mo₈ polyoxoanions connecting adjacent Ni1 along the c-axis generating another 1-D inorganic chain. As a result, the two kinds of 1-D chains cross each other forming a 2-D layer structure. The structures of 1 and 2 reveal that pH of the reaction system plays a crucial role in assembly of octamolybdate-based hybrid compounds. Investigation of the antitumor activities on SGC7901 and SMMC7721 cells of 1 and 2 indicates that the two new compounds possess selective antitumor activities, and their antitumor activities can be modulated by transition metal complexes.     

一个具有大Stokes位移的苯并噻唑类pH荧光探针

本文通过乙烯基将作为荧光团的苯并噻唑与作为H+受体的4-吡啶基桥联构筑了一个基于分子内电荷转移机制的pH荧光探针BTP2。研究表明该探针的Stokes位移为237 nm,远大于相应2-吡啶基类似物BTP1。滴定实验表明该探针的荧光在pH3.80至5.50之间随pH值增大而增强,且不受其他金属离子的干扰,具有检测胞内酸性细胞器pH的良好前景。探针pKa为4.72,略高于BTP1。4-吡啶基连接导致的更大的Stokes位移表明调节吡啶连接位置可以实现对该类探针分子Stokes位移的调控。     

A Model On-line Flow Injection Fluorescence Immunoassay Using a Protein a Immunoreactor and Lucifer Yellow

Abstract

A heterogeneous on-line fluorescence immunoassay has been developed for a model analyte (transferrin) using a flow injection analysis system containing a controlled pore glass protein A immunoreactor. Lucifer yellow VS (LYVS) a 4-aminonaphthalimide with a large stokes shift and pH independence was the fluorophore. For each assay the antibody-protein A reaction takes place at near neutral pH, and the complexes are eluted at acid pH. Transferrin levels in human serum has been determined by this method, and good within assay variations have been achieved.     

Spectrofluorimetric Determination of Gallium with 5-Bromosalicylidene-o-Aminophenol

Abstract

A method for the determination of trace amounts of gallium has been developed, based on the formation of a fluorescent complex between Ga (III) and 5-Bromosalicylidene-o-aminophenol (5-BrSOAPh). With excitation at 425 nm the chelate has an emission maximum at 520 nm. The reaction is carried out at apparent pH (pH?) 5.40 in an aqueous-ethanol medium (60% V/V ethanol). The influence of the reaction variables is discussed.