A highly selective chemodosimeter for the rapid detection of Hg2+ ions in aqueous media

A novel S,S′-diallyl carbohydrazonodithioate derivative 3 of rhodamine B hydrazone was developed as a chemodosimeter for selective detection of mercury ions based on Hg²⁺ promoted cyclization. The allyl groups of 3 play a key role in the binding and selection of Hg²⁺ ions. The probe responds selectively to Hg²⁺ over various other competitive cations with marked chromo- and fluorogenic changes. The formation of stable oxadiazole derivative 8 was a strong driving force for this high selectivity. Practically, this probe is more promising because of the remarkable high selectivity, faster response, low detection limit, and aqueous solubility of 3.     

Syntheses and characterization of Cu,Ni and Zn binding capability of histidinehydroxamic acid derivatives

Two histidinehydroxamic acid derivatives (N-methyl-histidinehydroxamic acid, N-Me-Hisha and Z-histidinehydroxamic acid, Z-Hisha) have been synthesized and their complexation with Cu²⁺-, Ni²⁺- and Zn²⁺-ions has been studied by using pH-potentiometric, UV–Vis, CD, ¹H NMR, EPR and ESI-MS methods. Both of the two new derivatives contain one donor atom less compared to the histidinehydroxamic acid (Hisha). In the case of N-Me-Hisha the hydroxamate-N as donor is eliminated, while the coordination of the amino-N of Z-Hisha is not possible at all.     

Stable iminonitroxide biradicals: Building blocks for organic heterospin,heteromolecular complexes

A stable cationic biradical has been designed and synthesized, and its magnetic property and crystal structure have been examined. An iminonitroxide derivative of 3,5-disubstituted pyridine (1) with a triplet ground state has been cationized by a reaction with methyl trifluoromethanesulfonate (MeTfO), which gave a salt of N-methylated pyridinium 2⁺, 2⁺ · TfO⁻. The ground state of the cation 2⁺ has been found to be triplet with 2J/k_B = 7.5 K from magnetic susceptibility measurements for 2⁺ · TfO⁻ in a magnetically diluted organic matrix. The magnetic susceptibility of neat crystalline solids of 2⁺ · TfO⁻ has been explained by an exchange coupling model based on the X-ray crystal structure. It is well known that the energy preference for a high-spin ground state for a m-phenylene coupling unit is disturbed by heteroatomic substitution and an ionic charge. The present experimental results show that the high-spin preference in 1 is little affected by the ionic charge in 2⁺. The ground-state triplet biradical serves as building blocks for molecule-based magnets of S > 1/2 of molecular assemblages based on electrostatic interactions between molecular ions.     

Alignment of atomic autoionizing states created by slow Na++He collisions

Ejected-electron spectra have been measured for collisions of He-atoms with Na⁺-ions, whose impact energy ranged from 1.7 to 7.0 keV. The ion impact-energy dependence of the angular-differential cross-section of the ejected electrons has been investigated for an aligned autoionizing state Na**(2p ⁵ 3s ^{2 2} P), which has been created by charge transfer from the He-atoms. The alignment of the autoionizing state Na**(2p ⁵ 3s ^{2 2} P) is discussed in relation to the scattering angles of the Na⁺-ions. A complete longitudinal alignment has been observed with respect to the quasimolecular axis.     

Alignment of atomic autoionizing states created by slow Li++Ne collisions

Ejected-electron spectra have been measured in collisions of Ne-atoms with Li⁺-ions, whose impact energy has been ranged from 0.4 to 7.0 keV. The ion impact-energy dependence has been investigated on the angular-differential cross-section of the ejected electrons from the aligned autoionizing state Ne** 2p ⁴3s ^{2 1} D. In the highest energies studied, cross section maxima have been found at both forward and backward angles with respect to the Li⁺-ion beam direction, whereas the cross sections are maximized at around right angles below intermediate energies. The data were analyzed semi-quantitatively, and the alignment of the autoionizing state was recognized to be characterized by a representative scattering angle of the Li⁺-ions.     

A new molecular building blocks: Synthesis,crystal structure,magnetic and spectroscopic properties of Cu(II) and Ni(II) macrocyclic complexes

New higly unsaturated macrocyclic building blocks [CuLSCN]·ClO₄ (1) (L = N-dl-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) and [NiL(SCN)₂] (2) (L = N-dl-5,12-dimethyl-7,14-diisopropyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) were synthesized and the crystal structures of both compounds were determined. Both complexes crystallizes in monoclinic, space group P2₁/n (1) and P2₁/c (2). Their magnetic properties were studied over the temperature range 1.8–300 K using a Quantum Design SQUID magnetometer (MPMSXL-5-type). The results indicate that both compounds behave as weakly interacting paramagnetic centers in the crystal lattice. The effects of hydrogen bond mediating the magnetic exchange interactions on the spin density have been evidenced by DFT calculations. The NIR–Vis–UV diffuse-reflectance electronic spectra confirm the square pyramidal and octahedral geometry around Cu²⁺ and Ni²⁺ metal ions.     

Gadolinium(III)–fluorescein complex as a dual modal probe for MRI and fluorescence zinc sensing

A bimodal imaging Gd–Zpy probe based on magnetic resonance imaging and fluorescence sensing has been synthesized and characterized. Gd–Zpy features a bright green emission and a turn-on fluorescent response manner with high sensitivity for Zn²⁺ in aqueous solution and is able to luminescent imaging intracellular Zn²⁺ levels within living cells. It exhibits a 130% increase of the longitudinal relaxation time and a 115% increase of transverse relaxive time upon addition of Zn²⁺. The results demonstrated that the incorporating of the fluorescein dye having the efficient chelators within a high-spin Gd³⁺ system was a powerful approach to achieve dual modal probes for MRI and fluorescence sensing.     

Magnetic properties of nitronylnitroxide and iminonitroxide triradicals as model compounds for generalized ferrimagnets

A novel iminonitroxide triradical, p-triIN (1), has been synthesized, in which a π-conjugated biradical with a singlet ground state and a doublet monoradical are united by σ-bonds. The intramolecular exchange interaction within the para-phenylene-based biradical moiety has been found to be antiferromagnetic (2J(π)/k_B = −30.8 K) from magnetic susceptibility measurements on a parent biradical, p-bisIN (2). The magnetic properties of 1 have been examined by magnetic susceptibility χ_m. Upon cooling, the χ_mT value for 1 has decreased and passed across 0.38 emu mol⁻¹ K, which is expected for one mol of S = 1/2 spin with g = 2.0. The magnetic behavior of 1 indicates that the ground state of the molecular assemblage of 1 in the crystal is diamagnetic, which is attributable to one of the exotic spin states as predicted in a theoretical model of generalized ferrimagnetism. The possible occurrence of the generalized ferrimagnetic spin alignment is concluded in view of the magnetic properties of 1.     

A highly selective ratiometric fluorescent chemosensor for Zn2+ ion based on a polyimine macrocycle

A new ratiometric fluorescent chemosensor based on a polyimine macrocycle ligand 1 has been synthesized. The chemosensor can exhibit a pronounced fluorescence response and high selectivity to Zn²⁺ ion over other 15 metal ions, including Cd²⁺. Sensor 1 appears an emission peak at 370 nm. Upon the addition of Zn²⁺ ion, the typical emission peak for 1 at 370 nm is obviously quenched, but a new emission peak at around 470 nm appears and shows a large enhancement due to the formation of a 1:1 Zn²⁺-1 complex. In addition, there is a good linear relationship between the fluorescence ratio I_470nm/I_370nm and the concentration of Zn²⁺, which makes a ratiometric assay of Zn²⁺ ion possible.     

Synthesis and metal extraction studies of a novel chromogenic 5,17-bisazocalix[4]arenes

Three novel chromogenic cone azocalix[4]arenes 5a–c, which have cavity and the azo groups as metal-binding sites and as coloration sites were synthesized. They were studied by the liquid–liquid extraction of selected metal cations (Sr²⁺, Ag⁺, Hg⁺, Hg²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cr³⁺, Al³⁺). Through examination of the extraction, a novel selectivity of these compounds toward Hg²⁺ cations has been determined. Besides, it has been also found that azocalix[4]arene 5c is highly sensitive to acid–base titration, which can be detected by the naked eye.     

On the magnetic structure of DyNiO3

The crystallographic structure of DyNiO₃ has been investigated at T=200, 100, and 2 K from high-resolution neutron powder diffraction (NPD) data. We show that the structure is monoclinic, space group P2₁/n, from the metal-insulator transition temperature at T_MI=564 K down to 2 K. The Ni atoms occupy two different sites 2d (Ni1) and 2c (Ni2), whose valences, estimated from bond-valence consideration, are +2.43(1) and +3.44(1) at 2 K, respectively. This is interpreted as the result of a partial charge disproportionation of the type 2Ni³⁺→Ni1^(3−δ)++Ni2^(3+δ)+, with δ≈0.55 at T=2 K. The magnetic structure has been studied from a NPD pattern at T=2 K, well below the establishment of the antiferromagnetic (AFM) ordering at T_N=154 K, as well as from sequential data collected from 16 K down to 2 K. The magnetic order is defined by the propagation vector k=(1/2,0,1/2). Two possible magnetic structures are compatible with the magnetic intensities. In the second solution both Ni sublattices participate in the magnetic order, as well as Dy since it corresponds to a total disproportionation of Ni³⁺ to Ni²⁺ and Ni⁴⁺. In the second solution both Ni sublattices participate in the magnetic order, as well as Dy. The magnetic moments for Ni1 and Ni2 atoms at T=2 K are 1.8 (2) and 0.8 (2) μ_B, respectively. These values are also compatible with a partial charge disproportionation. Dy³⁺ ions exhibit long-range magnetic ordering below 8 K. An abrupt contraction of the unit-cell volume is observed at this temperature, due to a magnetoelastic coupling. The magnetic moment for Dy³⁺ at T=2 K is 7.87 (6) μ_B.     

Der austausch des cyclopentadienylliganden im methylcyclopentadienyl-mangantricarbonyl : Darstellung und zusammensetzung der komplexe mit methyl-substituierten benzolen

The exchange of the cyclopentadienyl ring in methylcyclopentadienylmanganese(I) tricarbonyl by methy-substituted benzenes in the presence of aluminium halide leads to [arene-Mn(CO)₃]⁺-ions. The reaction conditions have been optimised; in addition to the yield the purity of the complexes has been determined in some detail. After mild decomposition the arenes were analysed by GLC. Pure [arene-Mn(CO)₃]⁺-ions can be isolated with benzene, toluene, m- and o-xylene.     

A sinapic acid–calix[4]arene hybrid selectively binds Pb over Hg and Cd

The binding affinity for Pb²⁺, Cd²⁺ and Hg²⁺ of the sinapic acid–calix[4]arene hybrid 2, having four sinapyl pendants at the upper rim, has been investigated via an UV–Vis study. Compound 2 has better complexing ability than the monomeric p-phenetidine derivative 1. This highlights that the clustering of sinapyl units in a basket-like structure, dictated by the calixarene scaffold, greatly enhances the complexing properties. Ligand 2 forms complexes even with Hg²⁺, which is not complexed by 1 at all; the complexes formed by 2 with Pb²⁺ and Cd²⁺ are much stronger than the analogous complexes formed by 1. The UV–Vis investigation shows that the hybrid 2 markedly favors Pb²⁺ over Cd²⁺ and Hg²⁺. Information on the structural properties of the complex species was obtained by ¹H NMR spectroscopy. NMR data show that all three metal ions are placed into the cavity consisting of the calixarene scaffold and the sinapyl pendants, though their binding affects the coordinating regions to a different extent.     

Syntheses,crystal structures and magnetic properties of complexes based on [Ni(L-L)3]2+ complex cations with dimethylderivatives of 2,2′-bipyridine and TCNQ

From the aqueous-methanolic systems Ni(NO₃)₂ – LiTCNQ – 5,5′-dmbpy and Ni(NO₃)₂ – LiTCNQ – 4,4′-dmbpy three novel complexes [Ni(5,5′-dmbpy)₃](TCNQ)₂ (1), [Ni(4,4′-dmbpy)₃](TCNQ)₂ (2) and [Ni(4,4′-dmbpy)₃]₂(TCNQ-TCNQ)(TCNQ)₂∙0.60H₂O (3), were isolated in single crystal form. The new compounds were identified using chemical analyses and IR spectroscopy. Single crystal studies of all samples corroborated their compositions and have shown that their ionic structures contain the complex cations [Ni(5,5′-dmbpy)]²⁺ (1) or [Ni(4,4′-dmbpy)]²⁺ (2 and 3). The anionic parts of the respective crystal structures 1–3 are formed by TCNQ^⋅- anion-radicals and in 3 also by a σ-dimerized dianion (TCNQ-TCNQ)^2- with a C-C distance of 1.663(5) Å. The supramolecular structures are governed by weak hydrogen bonding interactions. The variable-temperature (2–300 K) magnetic studies of 1 and 3 confirmed the presence of magnetically active Ni(II) atoms with S = 1 and TCNQ^⋅- anion-radicals with S = 1/2 while the (TCNQ-TCNQ)^2- dianion is magnetically silent. The magnetic behavior was described by a complex magnetic model assuming strong antiferromagnetic interactions between some TCNQ^⋅- anion-radicals.     

Single chemosensor for multiple analytes: chromogenic and fluorogenic detection for fluoride anions and copper ions

A o-hydroxybenzoyl-(N-butyl-4,6-naphthamimide) hydrazone (1) has been synthesized. Compound 1 displayed high selectivity for F^? and Cu²⁺ with UV/vis absorption and fluorescence spectra, respectively. In the presence of F^?, while the absorption peak of 1 showed the red shift, its fluorescent intensity decreased due to deprotonation interaction. In the presence of Cu²⁺, both the absorption and fluorescence peaks decreased because of the coordination interaction.     

New charge transfer salts of two organic π-donors of the tetrathiafulvalene type with the paramagnetic [Cr(NCS)6]3– anion

The electrochemical combination of the paramagnetic anion [Cr(NCS)₆]^3– with the organic π-donors bis(ethylenedithio)tetrathiafulvalene (ET) and 4,5-bis(2-hydroxyethylthio)-4′,5′-ethylenedithiotetrathiafulvalene (DHET–EDTTTF) leads to two new radical cation salts, namely (ET)₄[Cr(NCS)₆]·PhCN (1) and (DHET– EDTTTF)₂(NEt₄)[Cr(NCS)₆] (2). Both have been characterized by X-ray crystallography, magnetic and resistivity measurements. The structure of 1 consists of alternating inorganic layers generated by the anions and organic layers in which the PhCN molecules are inserted; the organic sub-lattice is built up from four different ET units, three of them with a charge distribution of +1, the fourth being neutral. The organic sub-lattice of 2 contains a centrosymmetric [(DHET–EDTTTF^•)₂]²⁺ dimer, in which the overlap mode is of the eclipsed type. Conductivity measurements indicate that compounds 1 and 2 are semiconductors with room temperature conductivities of 1.4 × 10^–2 and 6.1 × 10^–5 S cm^–1 and activation energies of 0.24 and 0.23 eV, in 1 and 2, respectively. For both salts, magnetic measurements indicate (i) that the organic and inorganic parts are magnetically independent, and (ii) that the organic units are antiferromagnetically coupled. To cite this article: F. Thétiot et al., C. R. Chimie 6 (2003).     

Synthesis, characterization and electrochemical properties of two new calix[4]arene derivatives bearing two ferrocene imine or ferrocene amine units at the upper rim

A novel calix[4]arene derivative with two ferrocenyl Schiff-base groups at the upper rim 3 has been synthesized from 5,17-diformyl-25,27-dipropoxy-26,28-dihydroxy calix[4]arene and 4-ferrocenylaniline via condensation reaction. Reduction of 3 with sodium borohydride led to calix[4]arene derivative 4 with two amino ferrocenyl groups at the upper rim. The ferrocenyl Schiff-base calix[4]arene and its corresponding reduced amine have been purified and characterized by elemental analysis,¹H NMR, FTIR, Mass and UV-vis spectral data. Electrochemical properties of compounds 3 and 4 have been investigated. Cyclic voltammograms of 3 and 4 show reversible redox couples of ferrocene/ferrocinium at E_1/2=0.401 V and 0.346 V, respectively. Electrochemical studies show these redox active compounds electrochemically recognize trivalent lanthanides La³⁺ and Ce³⁺ and divalent Pb²⁺ and Cu²⁺cations. With ferrocenyl Schiff-base calix[4]arene 3 an anodic shift as large as 130 mV is observed on addition of one equivalent of Ce³⁺ ion. Also extraction properties of compound 4 towards some metal cations have been described. It has been observed that compound 4 has a good selectivity for metal cations Fe³⁺, Cu²⁺, Pb²⁺ and Cd²⁺ against Ni²⁺ and Co²⁺.     

Effect of chemical composition and heat treatment condition on microstructure and magnetic properties of nanocrystalline BaDyxFe12−xO19 (x = 0.1, 0.2, 0.3, 0.4) microfibres

A series of BaDy_xFe_12?xO₁₉ ferrite microfibres have been synthesized from metal nitrates and citric acid by the sol–gel method. TG-DSC, XRD, FTIR, FESEM, TEM and VSM were employed to characterize the thermal decomposition process, crystallite sizes, structure and magnetic properties of ferrite microfibres. The effect of calcined temperature, holding time, ion substitution on structure, magnetic properties of barium ferrite microfibres was investigated. The nanoparticle growth mechanism of ferrite microfibres was discussed. The results indicated that the hexaferrite phase was formed at 750 °C and Dy³⁺ ions entered the magnetoplumbite lattice. However, the reflections shift to a lower angle and the characteristic peaks of ferrite microfibres in FTIR shift to the lower wavenumber with the Dy content increasing. The VSM results shown that saturation magnetization (M _s ) gradually increased with calcined temperature increasing and holding time prolonging, while coercive force (H _c ) revealed an increase at first and then decreases. With the Dy content increasing, the M _s achieved values of M _s  = 50 emu?g^?1 (297 K) and 70 emu?g^?1 (77 K) and the H _c value shown a continuous reduction from 515 kA??m^?1 (297 K) and 435 kA?m^?1 (77 K) (x = 0.0) to 242 and 215 kA?m^?1 (x = 0.4).     

Magnetic focusing of redox molecules at ferromagnetic microelectrodes

The electrochemical behavior of Fe and Ni disk-shaped microelectrodes (25 to 250 μm radius) in a uniform magnetic field (1 T) is reported. Magnetization of the ferromagnetic microelectrode generates a magnetic field gradient across the depletion layer that can be used to focus paramagnetic molecules toward the electrode surface. The magnetic force acting on the depletion layer is given by F_∇B=(χ/μ)B·∇B, where χ and μ are the volume magnetic susceptibility and magnetic permeability of the depletion layer, respectively, and B is the magnetic field. Magnetic field focusing of the nitrobenzene radical anion at Fe and Ni microelectrodes is demonstrated.     

Synthesis, crystal structure, spectroscopy and magnetic properties of a dinuclear Cu complex with 3,5-bis(2-pyridyl)pyrazole bridging ligand

A dinuclear Cu^II complex [Cu₂(bpp)₂(H₂O)₂](ClO₄)₂ (1) with 3,5-bis(2-pyridyl)pyrazole (Hbpp), has been synthesized and characterized by elemental analyses, thermal analysis, conductance, UV-vis and IR spectra. The crystal structure of 1, determined by X-ray diffraction technique, reveals that two centrosymmetric Cu^II centers are bridged by a pair of tetradentate anionic bpp ligands, adopting a square-pyramidal environment with the water ligand occupying the axial site. An interesting feature of this structure is the formation of a two-dimensional supramolecular network through O-H?O hydrogen bonds between the water moieties of the cationic [Cu₂(bpp)₂(H₂O)₂]²⁺ subunits and perchlorate anions. The magnetic properties of 1 have been investigated by variable-temperature magnetic susceptibility and EPR measurements. Very strong antiferromagnetic interaction between the Cu^II centers (with H=−JS₁S₂, J=−368.3 cm⁻¹) has been observed, and the magneto-structural correlations was analyzed.