The Application of Infrared Spectra to Structural Problems in Copper(II) Complexes of 2,2′-Bipyridine

The infrared spectra of the complexes [Cu(bipy)₃] (C10₄)^2′ [Cu(bipy)₂] (C10₄)₂, [Cu(bipy)₂I]I, [cu(bipy)₂I] C10₄ and [Cu(bipy)(C10₄)₂] (bipy - 2,2′-bipyridine) are discussed in relation to their known or probable structures. Evidence for tetragonal distortion of [Cu(bipy)₃]₂₊ but not [Cu(phen)₃]₂₊ (phen = 1, 10-phenanthroline) is adduced.     

A Rhodamine-Based Off�COn Fluorescent Chemosensor for Selectively Sensing Cu(II) in Aqueous Solution

A novel chromogenic and fluorogenic chemosensor RhB-pMOSal comprising a rhodamine fluorophore and a salicylaldehyde receptor being connected by an iminohydrazine link was synthesized and fully characterized. Its sensing behavior toward various metal ions in neutral aqueous solution was investigated by absorption and fluorescence spectroscopy. RhB-pMOSal exhibited a reversible and sensitive ??turn-on?? response of absorption and fluorescence toward Cu²⁺ in aqueous acetonitrile solution. Approximate 65 and 6-fold enhancement in the absorbance at 556 nm and fluorescence intensity at 573 nm were estimated when equivalent Cu²⁺ was added to the RhB-pMOSal solution. Under the same conditions, RhB-pMOSal displayed more sensitive than a reported analogue RhB-Sal to Cu²⁺ ion. The competition experiments for Cu²⁺ mixed with common metal ions exhibited no obvious change in absorption and emission except Cr³⁺ ion that can induce the fluorescence quenching of RhB-pMOSal to some extent.     

Spectral and Photophysical Properties of α-carboline (1-Azacarbazole) in Aqueous Solutions

The absorption and fluorescence spectra of α-carboline, 9H-pyrido[2,3-b]indole, AC, in organic aprotic solvents containing different water proportions and in acid/base aqueous solutions inside and outside the pH range have been examined. In the organic aprotic solvents, the addition of increasing concentrations of water sequentially quenches and shifts to the red the fluorescence spectra of AC. These spectral changes have been rationalized assuming the formation, at the lower water concentrations, of a discrete ground state non-cyclic weakly fluorescent AC hydrate emitting at 376 nm that, upon increasing the water concentrations, evolves to a higher order AC poly hydrate emitting at 397 nm. The changes of the AC absorption spectra in aqueous acid/basic solutions indicate the existence of three ground state prototropic species; the pyridinic protonated cation, C (pK_a?=?4.10?±?0.05), the neutral, N (pK_a?=?14.5?±?0.2), and the pyrrolic deprotonated anion, A. Conversely, the changes of the AC fluorescence spectra in these media indicate the existence of four excited state species emitting at 376 nm, 397 nm, 460 nm and 465 nm. Since the emissions at 376 nm and 397 nm satisfactorily match those of the hydrates observed in the organic-water mixtures, they were consistently assigned to two differently hydrated ground state N species. The remaining emissions at 460 nm and 465 nm have been assigned without ambiguity, on the basis of their excitation spectra, to the C and A species, respectively. The excited-state pK_as of the prototropic species of AC have been estimated by using the Förster-Weller cycle.     

Influence of Copper(II) Ions on Radicals in DOPA–Melanin

DOPA–melanin (DOPA = 3,4-dihydroxyphenyl-alanine) complexes with Cu(II) cations were studied by electron paramagnetic resonance (EPR) spectroscopy. After the addition of metal cations to the melanin polymer, the EPR spectra parameters were measured. The axial g-factor values are g _|| = 2.20 and g _^ = 2.0 5 g_{ \bot } = 2.0 5 . Since $ g_{||} > g_{ \bot } > 2 $ g_{||} > g_{ \bot } > 2 , the ground state orbital of the unpaired electron of the Cu(II) complex is | x ²  -   y ² ñ \left| {{{x}}^{ 2} } \right. \, - \, \left. {{{y}}^{ 2} } \right\rangle . Square coordination of these cations in melanin is proposed. The influence of the Cu(II) concentration in solution used during synthesis on the concentration of melanin radicals was investigated. Cu(II) cations causes the decrease in the paramagnetic center concentration in melanin. The Cu(II) EPR spectra are not saturated within the microwave power range of 0.7–70 mW used in our experiment.     

Highly Sensitive ‘on–off’ Pyrene Based AIEgen for Selective Sensing of Copper (II) Ions in Aqueous Media

A Fluorescent chemosensor based on pyrene scaffold, 5-diethylamino-2-(pyren-1-yliminomethyl)-phenol (PDS) is synthesized using condensation method. It displays novel aggregation-induced emission (AIE) phenomena in its aggregated/solid state. The AIE characteristic of PDS is studied in CH₃CN/H₂O mixtures at different volume percentage of water and morphology of the aggregated particles are investigated by DLS and optical fluorescence microscopic study. The probe is aggregated into ordered one-dimensional (1-D) rod like microcrystals and exhibit high efficiency of solid-state emission with green colour. By taking advantage of its interesting AIE feature, the aggregated hydrosol has been utilized as ‘off–on’ type fluorescence switching chemosensor with superb selectivity and sensitivity towards Cu²⁺ions and the limit of detection (LOD) was calculated as low as 6.3 µM. A high Stern–Volmer quenching constant was estimated to be 2.88?×?10⁵ M^?1. The proposed chemosensor with AIE feature reveals a prospective view for the on-site visual recognition of Cu²⁺ ions in fluorescent paper strips and the synthesized probe is also exploited to find out the concentration of Cu²⁺ions in real water samples.

     

A Phenylbenzothiazole Derived Fluorescent Sensor for Zn(II) Recognition in Aqueous Solution Through “Turn-On” Excited-State Intramolecular Proton Transfer Emission

A highly selective and sensitive fluorescent Zn²⁺ sensor N-(2-(benzo[d]thiazol-2-yl)phenyl)-2-((pyridin-2-ylmethyl)amino)acetamide (1) that derived from 2-(2′-aminophenyl)benzothiazole has been developed. In aqueous solution (HEPES/CH₃CN=4/6, v/v, HEPES 20 mM, pH?=?7.4), sensor 1 displays highly selective recognition to Zn²⁺ over other metal ions with a distinct longer-wavelength emission enhancement. Sensor 1 binds Zn²⁺ through its amide form with a 1:1 binding stoichiometry, which switched on the excited-state intramolecular proton transfer (ESIPT). Graphical Abstract

A simple 2-(2′-aminophenyl)benzothiazole-based fluorescent “off-on” sensor for Zn²⁺ recognition in HEPES/CH₃CN(4/6, v/v, HEPES 20 mM, pH?=?7.4) solution through switching on ESIPT has been developed.     

The Study of the Magnetic Properties of a Fe(III) Complex Solution by the NMR Method of “Stationary Coaxial Ampoule”

For the first time, the nuclear magnetic resonance method of “stationary coaxial ampoule” was used to study the temperature dependence of the paramagnetic contribution of iron-containing complex molecules to the volume magnetic susceptibility of a solution of this complex. It was found that when the complex [Fe(salten)Cl] is dissolved in the chloroform/toluene mixture (1:1), this dependence obeys the Curie–Weiss law. On the basis of the obtained dependence the value of the effective spin of the Fe(III) ion was calculated with high accuracy. The obtained value of S _eff for the Fe(III) ion agrees with the value found in the EPR study of the vitrified solution of this complex.     

ESR and optical study of Cu2+-doped bis-(5,5′-diethylbarbiturato)bis picoline Zn(II)

ESR studies were conducted on Cu²⁺-doped bis-(5,5′-diethylbarbiturato)bis picoline Zn(II). Two Cu²⁺ lattice sites, Cu²⁺(I) and Cu²⁺(II), were identified. These sites exhibit two sets of four hyperfine lines in all directions. The g factor and hyperfine splitting were calculated from ESR absorption spectra: g_x ?=?2.0201?±?0.002, g_y ?=?2.0900?±?0.002, g_z ?=?2.1634?±?0.002, A_x ?=?(30?±?2)?×?10^?4?cm^?1, A_y ?=?(40?±?2)?×?10^?4?cm^?1 and A_z ?=?(154?±?2)?×?10^?4?cm^?1. It was found that Cu²⁺ enters the lattice substitutionally. The ground-state wavefunction of the Cu²⁺ ion in this lattice was determined from the spin Hamiltonian constants obtained from the ESR studies. With the help of an optical absorption study, the nature of the bonding in the complex is also discussed.     

Luminescent Detection of ATP in Aqueous Solution Using Positively Charged CdSe–ZnS Quantum Dots

Commercially available CdSe–ZnS Quantum Dots (QDs) have been modified by exchanging the hydrophobic surface ligands with (2-mercaptoethyl)-trimethylammonium chloride. The resulting water soluble conjugate was titrated with solutions of adenosine triphosphate (ATP), adenosine diphosphate, adenosine monophosphate, guanosine triphosphate (GTP), guanosine diphosphate and guanosine monophosphate in 0.01 M 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer (pH 7.4). A strong fluorescence quench of about 80% was observed for ATP, a quench of 25% was observed for GTP while the others had virtually no effect. The quenching effect of ATP and GTP was attributed to the high negative charge density associated with these substrate’s resulting in a strong attraction to the QD surface enabling them to engage in electron transfer with the excited QD. The lack of fluorescence quenching associated with the other nucleotides was most likely due to their reduced charge density resulting in a lower affinity for the QD surface.     

The Solution of Dynamical Equation of Motion of IBM-Ⅱ in Continuous Variable Representation

In this article the solution of dynamical equation of motion of IBM-Ⅱ in continuous variable representation is discussed.With appropriate transformation and approximation,the on-phase part of system manifests the vibration-rotation mode and the off-phase part the 'scissor mode',ect.In the last section the energy spectrum of ¹⁵⁶Gd is calculated.The result can well reproduce the algebraic result of IBM-Ⅱ.     

Kinetics of Heterogeneous Isotopic Exchange of 60Co/Co3Co(CN)6 2 · 12 H2O in Aqueous Solution

The heterogeneous exchange reaction between cobalt ions in solution and Co₃Co(CN)_{6 2} · 12 H₂O has been studied. It is found that the exchange rate increases as the concentration of Co²⁺ ions in solution decreases. The results show that the exchange rate is controlled by the surface reaction at the solid-liquid interface. The activation parameters E_a, ΔH^#, ΔS^#, and ΔG^# are calculated.     

The EPR Spectrum of Di-μ-(pyridine N-oxide) bis [bisnitrato(pyridine N-oxide)copper(II)] in the Corresponding Zinc(II) Crystal

It has been shown^1–3 that the exchange interactions in the dimeric⁴ complex di-μ-(pyridine N-oxide) bis [bisnitrato(pyridine N-oxide) copper(II)], [Cu(pyO)₂]₂ lead to a triplet ground state for the copper(II) pairs. The triplet state epr spectrum has been observed^1,3,5,6 for a powdered sample of the complex coprecipitated with the corresponding zinc(II) complex, and the computer simulation of this spectrum has been carried out by two different groups^3,5,6. As is often the case when dealing with spectra of powdered samples, there exist ambiguities with the spectrum of [Cu(pyO)₂-(NO₃)₂]₂ since all of the resonances were not observed, and consequently, the interpretation and values of the parameters remain in question. It was felt that examination of the epr spectra of single crystal samples should permit a rigorous analysis of this problem.     

Properties of optical limitation of radiation in π-conjugated organic systems doped with fullerenes (The COANP-C70 system)

The effect of optical limitation of laser radiation in 2-cyclooctylamino-5-nitropyridine (COANP-C₇₀) doped with fullerene is experimentally studied. The energy density of the incident beam is measured to be ～4–4.5 J cm^?2 and the attenuation coefficients and the absorption spectrum of a new structure are determined. The photoinduced variation of the refractive index of the COANP-fullerene system and its influence on the optical limitation is studied in the visible range upon irradiation by nanosecond laser pulses. The mechanisms of optical limitation of radiation in these structures are specified. The nonlinear optical coefficients n ₂ and χ⁽³⁾ of the fullerene-doped π-conjugated COANP system are measured for the first time by the methods of dynamic holography.     

Spectroscopic Properties and Electronic Structure of (L-Glutamato)(2, 2′-Bipyridine) copper(II)

Cu(L-glu)(bpy)(L-glu = L-glutamato; bpy = 2, 2′-bipyridine) was prepared. Its electronic absorption spectrum and photoacoustic spectrum were recorded at room temperature. They were compared with each other and compared quantitatively with ligand field theory(LFT) and the radical wave function of non-free ions^[1–3]. Therefore, the electronic structure was also investigated with its spectrum behaviors and PLFT^[1–3].     

Study of Properties of Urea and L-α-Alanine Didoped Triglycine Sulfate (UrLATGS) Crystals

In this report, the properties of triglycine sulfate (TGS) crystals doped with urea and L--alanine were studied. Urea and L--alanine have successfully entered into TGS crystal, demonstrated by infrared transmission spectrum and pyroelectric study. Figures of merit and Curie temperature are increased due to these two additions. UrLATGS is more suitable for infrared detectors than pure TGS crystals.     

β-Cyclodextrin Effect on Micellization of Cetyltrimethyl ammonium Bromide in Aqueous Solution. Probed by Dual Fluorescence of Sodium P-Dimethylaminobenzoate

Effect of p-cyclodextrin (β-CD) on micellization of cetyltrimethylammonium bromide (CTAB) in aqueous solution was investigated by twisted intramolecular charge transfer (TICT) dual fluorescence of sodium p-dimethylaminobenzoate (SDMAB). It was shown that β-CD induces the micellization of CTAB and the aggregation of CTAB below CMC as well. A reduced charge density at CTAB micelle interface in the presence of β-CD, due to the incorporation of 1:1 CTAB-β-CD inclusion complex in micelle, was concluded to be the reason for β-CD induced micellization of CTAB.     

Semiempirical assignment of the electron transitions in manganese(II)-doped II–VI compounds

The electron transitions in manganese(II)-doped II–VI compounds have been assigned by the Angular Overlap Model (AOM). The extracted AOM and electron repulsion parameters are applied to assess the covalency of the respective manganese-ligand bonds. A comparison with Crystal Field Theory (CFT) is made in order to demonstrate the advantages offered by the AOM. The Dq values for Mn(II) in CdS and CdSe were found by interpolation from the Dq vs R⁻⁵_ml relation.     

The Complete Solution of the Classical SL(2,ℝ/U(1) Gauged WZNW Field Theory

We prove that any gauged WZNW model has a Lax pair representation, and give explicitly the general solution of the classical equations of motion of the SL(2,ℝ/U(1) theory. We calculate the symplectic structure of this solution by solving a differential equation of the Gelfand–Dikii type with initial state conditions at infinity, and transform the canonical physical fields non-locally onto canonical free fields. The results will, finally, be collected in a local B?cklund transformation. These calculations prepare the theory for an exact canonical quantization. Received: 9 June 1998 / Accepted: 7 March 1999     

The effects of polyethylene glycol and the coupling agent bis-(γ-triethoxysilylpropyl)-tetrasulfide (Si-69) on the interactions of silica-filled natural rubber

A Fourier Transform Infrared (FTIR) analysis using Fresnel Attenuated Total Reflectance (ATR) was performed on silica-filled cis-1,4-polyisoprene. Silica filler's detrimental effects on zinc-activated cure systems has been well documented. The silane coupling agent bis-(y-triethoxysilylpropyl)-tetrasulfide (Si-69) and polyethylene glycol (PEG) are industry standards used to offset the interactions caused by reaction between silica and the zinc-activated cure system. By adding PEG, it was found that the interaction peaks at 1040 and 1017 cm^-1 caused by the adsorption of natural rubber (NR) onto the surface of the silica were not formed. Also, by monitoring the zinc stearate peak at 1540 cm^-1, both Si-69 and PEG were found to reduce the soluble zinc ion reaction with the silica surface. Supporting evidence from the rheometer curves also shows that the additives reduce the cure retardation effects of the silica filler.     

The Properties of Light Pressure Force with High Order in Laser Fields

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