Synthesis and Characterization of a Biologically Active Lanthanum(III)–Catechin Complex and DNA Binding Spectroscopic Studies

A lanthanum(III) complex of catechin has been synthesized and characterized by elemental analysis, molar conductance, UV-Vis spectra, infrared spectra, thermal analysis, and ¹H NMR. The complex behaves as a nonelectrolyte in methanol solvent. The spectral and thermal properties of the complex are examined. A thermogravimetric (TGA) study showed the hydrated nature of the complex. ¹H NMR spectra of the lanthanum and the catechin (CT) ligands measured in CD₃OD-d₄ also show metal ligand coordination. The lanthanum–catechin complex shows bright luminescence in methanol solution. The interaction of the complex with calf thymus DNA has been investigated by absorption and emission spectroscopic measurements. Experimental spectral results suggest CT–DNA binding with catechin complex via an intercalative mode.     

Binding and Fluorescence Resonance Energy Transfer (FRET) of Ruthenium(II)-Bipyridine-Calixarene System with Proteins—Experimental and Docking Studies

The investigation of the interaction of ruthenium(II)-bipyridine-tert-butylcalix[4]arene complexes (Rubc2 and Rubc3) with proteins (BSA and ovalbumin) using absorption, emission, excited state lifetime and circular dichroism techniques and by docking studies show that luminophore-receptor system bind strongly with proteins. An enhancement of absorption as well as emission intensity of Ru(II)-calixarene complexes in the presence of proteins, but the quenching of the emission intensity of proteins in the presence of Ru(II)-calixarene complexes are the interesting observations. The enhancement of emission intensity of Ru(II)-calixarene complex, in the presence of proteins, is due to the fluorescence resonance energy transfer (FRET) from protein to Ru(II)-calixarene complex. Among the two Ru(II)-calixarene complexes synthesized Rubc3 has more efficient binding and energy transfer than Rubc2 and BSA, with a large cavity size, has the advantage for binding over ovalbumin. Docking studies reveal that the presence of tert-butylcalix[4]arene moiety in Ru(II)-calixarene complexes facilitates binding with proteins. After the binding of Rubc2 and Rubc3 with proteins, the nearby fluorophores present in proteins are in optimal distance from the ruthenium centre for efficient FRET process to occur.     

Synthesis, Characterization, and Luminescence Spectroscopic Accessibility Studies of tris(2,2′-Bipyridine)Ruthenium(II)-Labeled Inorganic-Organic Hybrid Polymers

The modified tris(2,2-bipyridine)ruthenium(II) complex 2 was anchored via a sol-gel process to different polysiloxane matrices to give a series of novel inorganic–organic hybrid polymers. One of the bipyridine ligands of 2 was provided with a long-chain spacer carrying a triethoxysilyl function (T group) at the end, which enables almost free mobility of the transition metal center. The polymers were swollen in several organic solvents of different polarity to investigate the luminescence behavior in the presence of quencher molecules. The luminescence of 2 was quenched using anthracene and atmospheric oxygen in appropriate concentrations of 5 · 10^–4 to 5 · 10^–3 and 3 · 10^–3 M, respectively. The luminescence behavior of 2 was determined by steady-state and time-resolved luminescence experiments. Translational mobilities of molecular species dissolved in the liquid phase were investigated by the kinetics of luminescence quenching after laser excitation. Both the translational mobility of anthracene and atmospheric oxygen, specified with the rate constant k₂ and the percentage of accessible luminescent centers were determined. Translational mobilities and the accessibility for anthracene and atmospheric oxygen in hybrid materials are significantly higher than in conventional Q type polysiloxanes.     

Preparation of Different Substitued Polypyridine Ligands,Ruthenium(II)-Bridged Complexes and Spectoscopıc Studies

Novel different substitued polypyridine ligands 4-((4-(1H-imidazo[4,5-f][1,10]phenanthroline-2-yl)phenoxy)methyl)benzaldehyde (BA-PPY), (E)-N-(4-((4-(1H-imidazo[4,5-f][1,10]phenanthroline-2-yl)phenoxy)methyl)benzylidene)-pyrene-4-amine (PR-PPY), (E)-N-(4-((4-(1H-imidazo[4,5-f][1,10] phenanthroline-2-yl)phenoxy)methyl)benzylidene)-1,10-phenanthroline-5amine (FN-PPY), 2-(4-(bromomethyl)phenyl)-1H-imidazo[4,5-f][1,10] phenanthroline (BR-PPY), 2-(4-(azidomethyl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline (N3-PPY) and triazole containing polypyridine ligand 3,4-bis[(4-(metoxy)-1,2,3-triazole)1-methylphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline)] benzaldehyde (BA-DIPPY) and Ruthenium(II) complexes were synthesized and characterized. Their photopysical properties were investigated. The complexes RuP(PR-PPY), RuB(PR-PPY, RuP(FN-PPY) and RuB(FN-PPY) exhibited a broad absorption bands at 485, 475, 476, and 453 nm, respectively, assignable to the spin-allowed MLCT (d_π–π*) transition. The emission maxima of the pyrene-appended polypyridine ligand PR-PPY was observed at λems = 616 nm and the phenanthroline-appended polypyridine ligand FN-PPY was observed at λems = 668 nm. And the emission maxima of the complexes RuP(PR-PPY), RuB(PR-PPY), RuP(FN-PPY) and RuB(FN-PPY) were observed at λems = 646, 646, 685 and 685 nm, respectively. As seen in fluorescence spectra, the fluorescence intensities of the ligands are higher than their metal complexes. This is because of quenching effect of Ruthenium(II) metal on chromophore groups.     

Synthesis and Reactivity of Mg(II)–Fe(II)–Fe(III) Hydroxycarbonates

Green rust-like compounds (GRs) were discovered as natural minerals in various hydromorphic soils, where anoxic conditions allow their stability. They may control some redox processes in aquifers and participate to the transformation of various pollutants. Since Mg(II) cations are present in the fields where GRs were discovered, a partial substitution of Mg(II) to Fe(II) leading to intermediate compounds between GRs and usual Mg(II)–Fe(III) hydroxysalts is suspected. Mg(II)–Fe(II)–Fe(II) hydroxycarbonates can be obtained as intermediate oxidation products of (Mg, Fe)(OH)₂ in carbonate-containing aqueous media obeying to [Fe^II _4(1–x)Mg^II _4x Fe^III ₂(OH)₁₂]²⁺ [CO₃ ^2– nH₂O]^–2. TMS spectra at 12 K are similar to those of GRs, i.e., two quadrupole doublets, one due to Fe(II) with a large isomer shift =1.29 mms^–1 (with respect to -iron at room temperature) and quadrupole splitting E _Q=2.76 mms^–1, the other one due to Fe(III) with smaller hyperfine parameters =0.49 mms^–1 and E _Q=0.44 mms^–1. Fe(II) ions oxidise rapidly into Fe(III) with dissolved O₂. The reactivity is similar to that of Fe(II)–Fe(III) hydroxysalts GR, and thus the potential of Mg(II)–Fe(II)–Fe(III) compounds for reducing pollutants.     

Synthesis, Characterization, DNA-Binding Properties of the Ln(III) Complexes with 6-Hydroxy Chromone-3-Carbaldehyde-(4′-Hydroxy) Benzoyl Hydrazone

6-Hydroxy chromone-3-carbaldehyde-(4′-hydroxy) benzoyl hydrazone (L) and its Ln (III) complexes, [Ln = La, Nd, Eu and Tb] have been prepared and characterized on the basis of elemental analyses, molar conductivities, mass spectra, ¹H NMR, thermogravimety/differential thermal analysis (TG-DTA), UV-vis spectra, fluorescence spectra and IR spectra. The formula of the complex is [Ln L·(NO₃)₂]·NO₃. Spectrometric titration, ethidium bromide displacement experiments and viscosity measurements indicate that Eu (III) complex bind with calf-thymus DNA, presumably via an intercalation mechanism. The intrinsic binding constant of Eu (III) with DNA was 2.48 × 10⁵ M⁻¹ through fluorescence titration data.     

Spectrophotometric and 27‐Al NMR Characterization of Aluminum(III) Complexes with l‐Histidine

Abstract

The complex formation between l‐histidine (HHis) and aluminum(III) ion in water solutions was studied by UV spectrophotometric and 27‐Al NMR measurements at 298 K. UV spectra were measured on solutions in which the total concentration of histidine was from 15.0 to 50.0 mmol/dm³ and the concentration ratio of histidine to aluminum was varied from 3∶1 to 10∶1 in the pH range between 4.2 and 6.0. The spectra were taken in the wavelength interval 240–340 nm. Nonlinear least‐squares treatment of the spectrophotometric data indicates the formation of the complexes Al(HHis)³⁺, Al(His)²⁺, Al(HHis)His²⁺, and Al₂(OH)His⁴⁺ with the overall formation constants β_p,q,r: log β_1,1,1=11.90±0.04, log β_1,1,0=7.25±0.08, log β_1,2,1=20.1±0.1, and log β_2,1,1=5.92±0.12 (p, q, r are stoichiometric indices for metal, ligand, and proton, respectively). ²⁷Al‐NMR spectra were taken on solutions with the concentration of aluminum 50 mmol/dm³ and that of histidine 250 mmol/dm³. In the pH interval 5.0–6.1, two resonances at 9.5 ppm and 12.0 ppm were assigned to Al(HHis)²⁺ and Al(HHis)(His)²⁺ (or Al(OH)(HHis)₂ ²⁺), respectively.     

Synthesis and Spectral Properties of Novel Fluorescent Poly(oxyethylene Phosphate) Tris(β-diketonate) Europium (III) Complexes

Novel poly(oxyethylene phosphate) tris(β-diketonate) europium (III) complexes have been synthesized by an improved procedure using the Atherton–Todd reaction conditions. N-ethyldiisopropylamine has been used as a mild base and propylene oxide as an acid scavenger in order to obtain poly(oxyethylene phosphate) in yield and purity higher than those achieved by conventional methods. The compounds have been characterized by ¹H, ¹³C, and ³¹P NMR and FTIR techniques. Their absorption, fluorescent excitation and emission spectra of chloroform and abs. ethanol solutions have been recorded and studied. The luminescent quantum yields and decay times have been determined and a dependence on the length of the oxyethylene spacer between phosphate groups has been established. The new polymer complexes are water soluble and have increased luminescence decay time in comparison with corresponding ternary complexes.     

Synthesis and Spectral Studies of Novel Co(II), Ni(II), Cu(II), Cd(II), and Fe(II) Metal Complexes with N-[5′-Amino-2,2′-bis(1,3,4-thiadiazole)-5-yl]-2-hydroxybenzaldehyde Imine (HL)

Co(II), Ni(II), Cu(II), Cd(II), and Fe(II) complexes with Schiff base derived from 2-amino-5-(2-amino-1,3,4-thiadiazolyl)-1,3,4-thiadiazole (1) and salicylaldehyde have been prepared. The ligand and its complexes have been characterized by IR, ¹H NMR spectra, elemental analyses, magnetic susceptibility, UV-Vis. and thermogravimetry–differential thermal analysis (TGA-DTA). The analytical data show 1:2 metal-to-ligand ratio for Co(II), Ni(II), Cd(II), and Fe(II) and 2:2 metal-to-ligand ratio for Cu(II) complexes. The suggested structures for the N-[5′-Amino-2,2′-bis(1,3,4-thiadiazole)-5-yl]-2-hydroxybenzaldehyde Imine (HL) complexes of Fe(II), Co(II), and Cd(II) are octahedral, for the Ni(II) complex is tetrahedral, and for the Cu(II) complex is square-planar     

Synthesis,Spectroscopic and Antimicrobial Investigations of Scandium(Ⅲ) Complexes with Four Kinds of Sulfa Drugs

Herein,this article was focused on the synthesis and discussed the spectroscopic characterizations of four new scandium(Ⅲ)sulfa-drug complexes.The nomenclature and symbols of these drugs were sulfadimidine(sulp-1),sulfanilamide(sulp-2),sulfamethoxazole(sulp-3)and sulfadiazine(sulp-4).The microanalytical and spectroscopic analyses which utilized in this study were micro-analyses,magnetic,FT-IR,UV-Vis techniques.The mid infrared spectra deduced that the four sulfa-drug chelates acts as a bidentate chelates with scandium(Ⅲ)ion via two nitrogen atoms of-NH2-Ar and-NH-SO2 groups.Also,the FTIR spectra of Sc3+complexes referred to the existed of new medium weak bands in the range of 500~400 cm^-1 due to stretching vibration bands ofν(M-N).The elemental analysis technique confirmed the 1∶2 stoichiometry between Sc3+ions and sulp ligand with molecular formula[Sc(sulp)2(Cl)2]·Cl.At room temperature,the results of magnetic measurements for the Sc(Ⅲ)complexes indicated that all of the synthesized complexes have a diamagnetic character with octahedral configuration.The electronic spectra of the free sulfa-drug ligands shows band at 275 and 310 nm which are intraligand charge transfer band.The electronic sbsorption spectra of the Sc3+complexes were recorded using DMSO solvent.The spectra of complexes display bands within 275~388 nm,which attributed toπ-π*,n-π*and charge-transfer M-LCT electronic transitions,which strongly favors the octahedral geometry around Sc(Ⅲ)metal ions.1HNMR spectra of complexes referred to the downfield proton shifts of the-NH2 and NHSO2 groups,which supported the place of coordination.The half maximal inhibitory concentration(IC50)of the ScⅢcomplexes was assessed against the human hepato cellular carcinoma(HepG-2)tumor cell line.     

Dimeric Fe (II, III) complex of quinoneoxime as functional model of PAP enzyme: Mössbauer, magneto-structural and DNA cleavage studies

Purple acid phosphatase, (PAP), is known to contain dinuclear Fe₂ ^?+?2,?+?3 site with characteristic Fe^?+?3 ← Tyr ligand to metal charge transfer in coordination. Phthiocoloxime (3-methyl-2-hydroxy-1,4-naphthoquinone-1-oxime) ligand L, mimics (His/Tyr) ligation with controlled and unique charge transfers resulting in valence tautomeric coordination with mixed valent diiron site in model compound Fe-1: [μ-OH-Fe₂ ^?+?2,?+?3 (o-NQ_CH3ox) (o-NSQ_CH3ox)₂ (CAT) H₂O]. Fe-2: [Fe^?+?3(o-NQ_CH3ox) (p-NQ_CH3ox)₂]₂ a molecularly associated dimer of phthiocoloxime synthesized for comparison of charge transfer. ⁵⁷Fe Mössbauer studies was used to quantitize unusual valences due to ligand in dimeric Fe-1 and Fe-2 complexes which are supported by EPR and SQUID studies. ⁵⁷Fe Mössbauer spectra for Fe-1 at 300 K indicates the presence of two quadrupole split asymmetric doublets due to the differences in local coordination geometries of [Fe^?+?3]_A and [Fe^?+?2]_B sites. The hyperfine interaction parameters are δ _A = 0.152, (ΔE _Q)_A = 0.598 mm/s with overlapping doublet at δ _B = 0.410 and (ΔE _Q)_B = 0.468 mm/s. Due to molecular association tendency of ligand, dimer Fe-2 possesses 100% Fe^?+?3(h.s.) hexacoordinated configuration with isomer shift δ = 0.408 mm/s. Slightly distorted octahedral symmetry created by NQ_CH3ox ligand surrounding Fe^?+?3(h.s.) state generates small field gradient indicated by quadrupole split ΔE _Q = 0.213 mm/s. Decrease of isomer shifts together with variation of quadrupole splits with temperature in Fe-1 dimer compared to Fe-2 is result of charge transfers in [Fe₂ ^?+?2,?+?3 SQ] complexes. EPR spectrum of Fe-1 shows two strong signals at g ₁ = 4.17 and g ₂ = 2.01 indicative of S = 3/2 spin state with an intermediate spin of Fe^?+?3(h.s.) configuration. SQUID data of $\chi _m^{{\rm corr}} \mbox{.T}$ were best fitted by using HDVV spin pair model S = 2, 3/2 resulting in antiferromagnetic exchange (J = ?13.5 cm^???1 with an agreement factor of R = 1.89 × 10^???5). The lower J value of antiferromagnetic exchange leads to Fe⁺³μ-(OH) Fe^?+?2 bridging in Fe-1 dimer instead of μ-oxo bridge. The intermolecular association through H-bonds may lead to weakly coupled antiferromagnetic interaction between two Fe-2 molecules having Fe^?+?3(h.s.) centers. Using S = 5/2, 5/2 spin pair model we obtained best-fitted parameters such as J = ?12.4 cm^???1, g = 2.3 with R = 3.58 × 10^???5. Synthetic strategy results in non-equivalent iron sites in Fe-1 dimer analogues to PAP enzyme hence its reconstitution results in pUC-19 DNA cleavage activity, as physiological functionality of APase. It is compared with nuclease activity of Fe-2 RAPase.     

M?ssbauer spectroscopic study on valence-detrapping and trapping of mixed-valence trinuclear iron(III, III, II) fluorine-substituted benzoate complexes

Magnetorheological (MR) fluids are new iron-based materials, whose applications include brakes, dampers, clutches, shock absorbers systems and polishing of optical surfaces (lens and mirrors). They are dependent on the size and shape of particles as the magnetic properties. Interested in the possibility of using iron-rich powders, commonly used in nondestructive testing, ranging in size from a few μm to about 200?μm and lower cost than those commercially used for MR fluids, a study of the structural and magnetic properties of iron-rich metallic particles by X-ray diffraction (XRD) and M?ssbauer spectroscopy (MS) at room temperature has been done. Powders, as received, were separated into particle sizes smaller than 20?μm (sample A) and in the range of 20–38?μm (sample B) because these are the sizes generally required for applications in MR fluids. The particles whose sizes exceed the above values were ground in a high energy planetary mill for 3?h, using different values of rotational speed/time: 200?rpm for one hour, a pause of 10?s, 140?rpm for one hour, pause 10?s and then 175?rpm during the last hour. These powders were sieved to obtain particles smaller than 20?μm (sample C). According XRD results, in all samples, only α-Fe (lattice parameter a = 2,867(2) ?) and Fe₂O₃ (lattice parameter a = 5,037(1) ? and c = 13,755(8) ?) were present. The M?ssbauer spectra were fitted with two sextets. The hyperfine parameters values allowed us to assign the highest relative area spectrum (sextet) corresponding to α-Fe and the second one to Fe₂O₃ in accord to the XRD results. Thus, the preparation method using mechanical milling for diminishing the size of the metallic particles allowed us to get particles with size and magnetic properties that could lead to potentially MR fluids applications.     

EPR Studies of DOPA–Melanin Complexes with Netilmicin and Cu(II) at Temperatures in the Range of 105–300?K

The application of electron paramagnetic resonance (EPR) spectroscopy in pharmacy of melanin complexes with netilmicin and Cu(II) was presented. The continuous microwave saturation of EPR spectra of DOPA–melanin and the complexes was performed. EPR spectra were measured on an X-band (9.3?GHz) spectrometer at temperatures in the range of 105–300?K. Paramagnetic copper ions decrease the intensity of the EPR lines of melanin’s free radicals. It was found that fast spin–lattice relaxation characterizes DOPA–melanin–Cu(II) complexes. Slow spin–lattice relaxation processes exist in melanin’s paramagnetic centers of DOPA–melanin and DOPA–melanin–netilmicin, [DOPA–melanin–netilmicin]–Cu(II), [DOPA–melanin–Cu(II)]–netilmicin complexes. Spin–lattice relaxation processes are faster at higher temperatures. The homogeneous broadening of EPR lines for melanin complexes was observed. The practical consequences of differences between paramagnetic properties of melanin complexes with netilmicin and the complexes with Cu(II) were discussed.     

Synthesis,phase stability and oxide ion conductivity of Ce(IV)–Cd(II) double substituted bismuth vanadate

Bi₄V₂O_11-δ has been doped with Ce and Cd to study double substitution. The system with various dopant concentrations (0.07 ≤ x ≤ 0.30) was prepared by the standard solid-state reaction method. The correlation between the polymorphism and oxide ion performance was well investigated as a function of temperature and composition with the help of thermal analysis, X-ray diffraction (XRD) and AC impedance spectroscopy. From XRD results it is seen that the high oxide ion conducting tetragonal γ-phase is stabilized for x = 0.17. For the compositions x ≤ 0.10, monoclinic α-phase is retained at room temperature with clear evidence for two successive phase transitions α ? β and β ? γ. For x = 0.13, β ? γ phase transition is seen. However, the existence of order–disorder, γ' ? γ transition was confirmed for x = 0.17. It is seen that the highest low-temperature ionic conductivity at 320 °C is 3.19 × 10^?4 S cm^?1 which was observed for x = 0.17.     

Synthesis, Photo-physical and DFT Studies of ESIPT Inspired Novel 2-(2′,4′-Dihydroxyphenyl) Benzimidazole, Benzoxazole and Benzothiazole

Novel ESIPT inspired benzimidazole, benzoxazole and benzothiazole were synthesized from 2,4-dihydroxy benzoic acid and 1,2-phenelenediamine, 2-aminophenol, and 2-aminothiophenol respectively. The synthesized 2-(2′,4′-dihydroxyphenyl) benzimidazole, benzoxazole and benzothiazole are fluorescent and the emission characteristic are very sensitive to the micro-environment. They show a single absorption and dual emission with large Stokes shift originating from excited state intramolecular proton transfer. The absorption-emission characteristics of all these compounds are studied as a function of pH. The change in the electronic transition, energy levels, and orbital diagrams of synthesized compounds were investigated by the molecular orbital calculation and were correlated with the experimental spectral emission. Experimental absorption and emission wavelengths are in good agreement with those predicted using the Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) [B3LYP/6-31G(d)].

Synthesis,Structural,Spectroscopic Characterization and Biological Properties of the Zn(Ⅱ),Cu(Ⅱ),Ni(Ⅱ),Co(Ⅱ),and Mn(Ⅱ) Complexes With the Widely Used Herbicide 2,4-Dichlorophenoxyacetic Acid

2,4-Dichlorophenoxyacetic acid (2,4-D) is a board-leaf selective herbicide and globally used in agricultural activities. Complexation mode, spectroscopic investigations and biological properties of complexes formed between 2,4-D (C₆H₃Cl₂OCH₂·COOH; HL) with Zn(Ⅱ), Cu(Ⅱ), Ni(Ⅱ), Co(Ⅱ), and Mn(Ⅱ) metal ions were investigated. To characterize the binding mode between 2,4-D and the metal ions, many physicochemical approaches were employed. The complexes obtained are characterized quantitatively and qualitatively by using micro elemental analysis, FTIR spectroscopy, UV-Vis spectroscopy, 1H-NMR, and magnetic susceptibility measurements. Results of these approaches suggested that the gross formula of the complexes obtained with the metal ions were [ZnL₂](2H₂O (1), [CuL₂(H₂O)₂] (2), [NiL₂](3H₂O (3), [CoL₂(H₂O)₂] (4), and [MnL₂(H₂O)₂] (5). In all complexes, two L- anion were coordinated the metal ion by their bidentate carboxylate groups. From the spectral study, all the complexes obtained as monomeric structure and the metals center moieties are six-coordinated with octahedral geometry except Ni(Ⅱ) and Zn(Ⅱ) complexes which existed as a tetrahedral and square pyramidal geometry respectively. The complexes were screened in vitro against several microbes (fungi and bacteria) using Kirby-Bauer disc diffusion method, and data has demonstrated that complex 3 showed excellent antifungal activity.     

Synthesis,phase formation,and properties of nanomaterials based on the titanium dioxide−iron(III) oxide binary system

The properties of nanomaterials based on the titanium dioxide?iron(III) oxide binary system prepared by low-temperature coprecipitation from aqueous solutions are studied. The effect of thermal treatment conditions and other factors on the process of phase formation and the properties of the synthesized products is examined. It is demonstrated that these materials have a relatively low photocatalytic activity but a high sorption capacity.     

Synthesis,Spectroscopic Characterization and Thermogravimetric Analysis of Cr(Ⅱ), Cu(Ⅱ), Zn(Ⅱ) and Mg(Ⅱ),Captopril Coordination Compounds

In this work,we have reported the synthesis and spectroscopic characterization of captopril(Cap)coordination compounds:Cu(Cap)·2H 2O,Cr(Cap)·H 2O,Zn(Cap)·3H 2O and Mg(Cap)4.Herein,it is worthily mentioned that the FTIR spectroscopic technique was employed to recognized the nature of coordination between captopril ligand and copper,chromium,zinc and magnesium(Ⅱ)metal ions.In view of the infrared spectroscopic tool,the copper(Ⅱ)metal ion coordinated toward captopril drug ligand through sulfur atom of SH group dependent on the absent of stretching vibration band of—SH.Based on this result,the stretching motion ofνa(COO)shifts clearly indicates that Cu 2+,Cr 2+,Zn 2+and Mg 2+the carboxylic group is employed as coordinative site for all compounds as a metal-ligand coordinative bond.As a general behavior,it is verified that the coordination compound thermal stability(considering the release of captopril molecules,not the release of water molecules)is affected by the metal cation radius:minor radius is associated with higher thermal stability,probably due to a higher metal-captopril bond dissociation enthalpy.     

Fluorescence “Switch on” of Conjugates of CdTe@ZnS Quantum Dots with Al, Ni and Zn Tetraamino-Phthalocyanines by Hydrogen Peroxide: Characterization and Applications as Luminescent Nanosensors

In this study, we have developed a novel nanoprobe for H₂O₂ based on the conjugation of CdTe@ZnS quantum dots (QDs) to different metal tetraamino-phthalocyanine (MTAPc): (M?=?(OAc)Al, {OAc?=?acetate}, Ni and Zn). Chemical coordination of the QDs to the MTAPc resulted in the fluorescence “switch off” of the linked QDs which was associated with Förster resonance energy transfer (FRET). In the presence of varying concentration of H₂O₂, the fluorescence of the linked QDs was progressively “switched on” and the FRET mechanism between the QDs and the MTAPc was disrupted. The sensitivity/limit of detection of the nanoprobe followed the order: QDs-ZnTAPc (2.2 μM)?>?QDs-NiTAPc (4.4 μM)?>?QDs-AlTAPc (9.8 μM) while the selectivity followed the order: QDs-NiTAPc?>?QDs-AlTAPc?>?QDs-ZnTAPc. The varying degree of sensitivity/selectivity and mechanism of detection is discussed in detail.     

Synthesis,Spectroscopic Characterization,Thermogravimetric and Biological Activity Evaluation of Te(Ⅳ),Se(Ⅳ),V(Ⅲ),Nb(Ⅴ),Ta(Ⅴ)Complexes With Indole-3-Acetic Acid Plant Hormone Ligand

Te(Ⅳ), Se(Ⅳ), V(Ⅲ), Nb(Ⅴ) and Ta(Ⅴ) complexes of indole-3-acetic acid (IAAH) ligand were synthesized, characterized by elemental analysis and various spectroscopic techniques like, IR, 1H-NMR, X-ray powder diffraction, UV-Visible, thermogravimetry analysis, magnetic measurements, molar conductance and surface morphology using SEM. All the synthesized complexes of IAAH ligand have 1∶2 stoichiometry of the types [Te(IAA)₂(NH₃)₂]·2Cl (Ⅰ), [Se(IAA)₂(NH₃)₂]·2Cl (Ⅱ), [V(IAA)₂(NH₃)(Cl)] (Ⅲ), [Nb(IAA)₂(Cl)₃] (Ⅳ), and [Ta(IAA)₂(Cl)₃] (Ⅴ). Spectral analysis indicates octahedral geometry for the Te(Ⅳ), Se(Ⅳ) and V(Ⅲ) complexes, whereas both Nb(Ⅴ) and Ta(Ⅴ) have a seven-coordination. The bonding sites are the oxygen atoms of carboxylate group for the deprotonated indole-3-acetic acid (IAA) ligand. The thermogravimetry analysis studies gave evidence for the presence of other coordinated molecules (Cl or NH₃) in the composition of IAA complexes, which were further supported by IR and micro analytical measurements. The higher molar conductance data of tellurium and selenium (Ⅳ) complexes reveal that these chelates are electrolytes, while low conductivity values for the vanadium(Ⅲ), niobium and tantalum(Ⅴ) chelates indicated a non-electrolytes. To test the antibacterial property of the five complexes in this study, four bacterial strains Klebsiella (G-), Escherichia coli (G-), Staphylococcus aureus (G+) and Staphylococcus epidermidis (G+) were used in the investigation. The effects of the five complexes in the cytotoxicity of Caco-2 and Mcf-7 human cancer cell lines were studied Neutral red uptake assay for the estimation of cell viability/cytotoxicity protocol.