Recent advancement on chromo-fluorogenic sensing of aluminum(III) with Schiff bases

The consumption of non-essential aluminum ion (Al³⁺) at higher concentration from biotic and abiotic sources can cause serious adverse effects to the human body. Therefore, there is bourgeoning need of developing facile analytical methods for the on-site and real-time monitoring of Al³⁺ concentration in various environmental and biological samples. The chromo-fluorogenic based sensors have been widely developed in the recent years to detect and monitor Al³⁺ ion. Among the various types of developed chemical sensors, the Schiff bases proved to have several advantages due to their facile synthesis with high yield, fascinating coordination behavior and easy structural modification. This review was narrated to compile the Schiff bases introduced recently for the sensing of Al³⁺ in various environmental and biological samples. The designing of sensor, sensing mechanisms and other analytical novelties of the developed sensors are discussed.     

Chiral Ligands in Hypervalent Iodine Compounds: Synthesis and Structures of Binaphthyl-Based λ3-Iodanes

Several novel binaphthyl-based chiral hypervalent iodine(III) reagents have been prepared and structurally analysed. Various asymmetric oxidative reactions were applied to evaluate the reactivities and stereoselectivities of those reagents. Moderate to excellent yields were observed; however, very low stereoselectivities were obtained. NMR experiments indicated that these reagents are very easily hydrolysed in either chloroform or DMSO solvents leading to the limited stereoselectivities. It is concluded that the use of chiral ligands is an unsuccessful way to prepare efficient stereoselective iodine(III) reagents.     

An Expedient Method for the Umpolung Coupling of Enols with Heteronucleophiles**

In this paper, we present an unprecedented and general umpolung protocol that allows the functionalization of silyl enol ethers and of 1,3-dicarbonyl compounds with a large range of heteroatom nucleophiles, including carboxylic acids, alcohols, primary and secondary amines, azide, thiols, and also anionic carbamates derived from CO₂. The scope of the reaction also extends to carbon-based nucleophiles. The reaction relies on the use of 1-bromo-3,3-dimethyl-1,3-dihydro-1λ³[d][1,2]iodaoxole, which provides a key α-brominated carbonyl intermediate. The reaction mechanism has been studied experimentally and by DFT, and we propose formation of an unusual enolonium intermediate with a halogen-bonded bromide.     

Effective biosorption of arsenic from water using La(III) loaded carboxyl functionalized watermelon rind

Arsenic is highly toxic and carcinogenic element that mainly enters into our body through drinking water and caused adverse effect even at low concentration. A new type of cation exchanger is developed from waste biomass of watermelon rind after increasing the carboxyl functional groups by saponification. Saponified Watermelon Rind (SWR) was further loaded with La(III) to attenuate the contamination of As(III) from water. Characterization of biosorbent was performed using Fourier Transform Infra-Red (FTIR) spectroscopy, Field emission Scanning Electron Microscopy (Fe-SEM,) Energy Dispersive X-ray (EDX) spectroscopy and zeta potential analysis. Arsenic speciation of sorption product through X-ray photoelectron spectroscopic (XPS) analysis revealed that As(III) is partially converted into As(V) during biosorption process. The biosorption tests for As(III) were explored under different operating conditions. La(III)-SWR towards As(III) biosorption was best described by Langmuir biosorption isotherm and pseudo second order kinetic model. At a pH of 12.08, the optimum biosorption capacity was found to be 37.73 ± 0.12, 48.78 ± 0.09, 62.50 ± 0.11 mg/g, respectively at temperatures 298 K, 303 K and 308 K. The existance of chloride and nitrate showed negligible interference whereas sulphate and phosphate significantly inhibits As(III) biosorption. Thermodynamic study showed spontaneous and endothermic nature As(III) biosorption onto La(III)-SWR. The sorbed As(III) was eluted almost completely using 2 M NaOH. The findings of this study insinuated that La(III)-SWR biosorbent investigated in this study can be a low cost, environmentally benign and eco-friendly material for the treatment of aqueous solution polluted with arsenic ions.     

pH-Responsive N^C-Cyclometalated Iridium(III) Complexes: Synthesis,Photophysical Properties,Computational Results,and Bioimaging Application

Herein we report four [Ir(N^C)₂(L^L)]ⁿ⁺, n = 0,1 complexes (1–4) containing cyclometallated N^C ligand (N^CH = 1-phenyl-2-(4-(pyridin-2-yl)phenyl)-1H-phenanthro[9,10-d]imidazole) and various bidentate L^L ligands (picolinic acid (1), 2,2′-bipyridine (2), [2,2′-bipyridine]-4,4′-dicarboxylic acid (3), and sodium 4,4′,4″,4‴-(1,2-phenylenebis(phosphanetriyl))tetrabenzenesulfonate (4). The N^CH ligand precursor and iridium complexes 1–4 were synthesized in good yield and characterized using chemical analysis, ESI mass spectrometry, and NMR spectroscopy. The solid-state structure of 2 was also determined by XRD analysis. The complexes display moderate to strong phosphorescence in the 550–670 nm range with the quantum yields up to 30% and lifetimes of the excited state up to 60 µs in deoxygenated solution. Emission properties of 1–4 and N^CH are strongly pH-dependent to give considerable variations in excitation and emission profiles accompanied by changes in emission efficiency and dynamics of the excited state. Density functional theory (DFT) and time-dependent density functional theory (TD DFT) calculations made it possible to assign the nature of emissive excited states in both deprotonated and protonated forms of these molecules. The complexes 3 and 4 internalize into living CHO-K1 cells, localize in cytoplasmic vesicles, primarily in lysosomes and acidified endosomes, and demonstrate relatively low toxicity, showing more than 80% cells viability up to the concentration of 10 µM after 24 h incubation. Phosphorescence lifetime imaging microscopy (PLIM) experiments in these cells display lifetime distribution, the conversion of which into pH values using calibration curves gives the magnitudes of this parameter compatible with the physiologically relevant interval of the cell compartments pH.     

FeIII in a high-spin state in bis(5-bromosalicylaldehyde 4-ethylthiosemicarbazonato-κ3O,N1,S)ferrate(III) nitrate monohydrate,the first example of such a cationic FeIII complex unit

The synthesis and crystal structure (100 K) of the title compound, [Fe(C₁₀H₁₁BrN₃OS)₂]NO₃·H₂O, is reported. The asymmetric unit consists of an octahedral [Fe^III(HL)₂]⁺ cation, where HL^? is H-5-Br-thsa-Et or 5-bromosalicylaldehyde 4-ethylthiosemicarbazonate(1?) {systematic name: 4-bromo-2-[(4-ethylthiosemicarbazidoidene)methyl]phenolate}, a nitrate anion and a noncoordinated water molecule. Each HL^? ligand binds via the thione S, the imine N and the phenolate O atom, resulting in an Fe^IIIS₂N₂O₂ chromophore. The ligands are orientated in two perpendicular planes, with the O and S atoms in cis and the N atoms in trans positions. This [Fe(HL)₂](anion)·H₂O compound contains the first known cationic Fe^III entity containing two salicylaldehyde thiosemicarbazone derivatives. The Fe^III ion is in the high-spin state at 100 K. In addition, a comparative IR spectroscopic study of the free ligand and the ferric complex is presented, demonstrating that such an analysis provides a quick identification of the degree of deprotonation and the coordination mode of the ligand in this class of metal compounds. The variable-temperature magnetic susceptibility measurements (5–320 K) are consistent with the presence of a high-spin Fe^III ion with a zero-field splitting D = 0.439 (1) cm^?1.     

Spectral and thermal features of some novel iron(III) chelates with substituted 2-hydroxyaryloximes

The reaction products of five substituted 2-hydroxyaryloximes with Fe(III) ion were obtained and characterized by means of elemental analysis, conductometric measurements, magnetic moment determinations and spectroscopic data (IR and electronic absorption).The thermal stability and mode of decomposition were studied in air atmosphere by using TG-DTA. Kinetic analysis of the TG data was performed with the Coats-Redfern method to determine the apparent activation energies and the pre-exponential factor of the Arrhenius equation. Mass spectrometry was also used, and possible fragmentation patterns are given and discussed.Thanks are due to Tekkosha Hellas, Thessaloniki, for making available the thermogravimetric analysis facilities.     

Kinetic analysis of thermogravimetric data

Thermal decomposition of 6 complexes of the type AH[Cr(NCS)₄ (am)₂]· nH₂O is studied with derivatograph. The formation of Cr(NCS)₃ as a labile intermediate is presumed. For some decomposition stages kinetic parameters are derived. The kinetic compensation effect is discussed.     

Determination of lutetium by fluorimetry, using BPMPHD and CTMAB

Lutetium(III) forms an association compound with a new synthetic reagent, 1,6-bi(1-phenyl-3-methyl-5-pyrazolone-4)hexandione (BPMPHD), and cetyltrimethylammonium bromide (CTMAB). The compound enhances the natural fluorescence of BPMPHD remarkably, upon which a new fluorescence method was developed for determining lutetium in rare earth (RE) samples. The determination range was 1.80 × 10^–7–8.8 × 10^–6 g/ml. The determination limit was 29 ng/ml. The composition of the ion associate was [Lu(BPMPHD)₂]–CTMAB⁺.     

Ferric borate formation in aqueous solution

Potentiometric analyses indicate that previous investigations have overestimated the stability of ferric borate complexes. The FeB(OH) ₄ ²⁺ formation constant result obtained in the present work is_Bβ ₁ ^* = [FeB(OH) ₄ ²⁺ ][H⁺][Fe³⁺]^-1[B(OH)₃]^-1 = (5.4±0.3) x 10^-3 at 25.0°C and 0.7 molal ionic strength. Our result indicates that solution concentrations of FeOH²⁺ and FeB(OH) ₄ ²⁺ are approximately equal in aqueous solution for boric acid concentrations on the order of 0.3 molal. Fe(B(OH)₄) ₂ ⁺ is a minor species in solution compared to FeB(OH)₄ ²⁺ for conditions such that [B(OH)₃][H⁺]^-1≤ 350, and ferric borate complexation is insignificant in solutions such as seawater where [B(OH)₃] ≤ 4× 10^-4 molal.