Crystal structure,ionic conductivity and dielectric relaxation studies in the (C5H10N)2BiBr5 compound

The synthesis and crystal structure of the bis (3-dimethylammonium-1-propyne) pentabromobismuthate(III) salt are given in the present paper. After an X-ray investigation, it has been shown that the title compound crystallizes at 298 K in a centrosymmetric monoclinic system, in the space group C₂/c with the following lattice parameters a=12.9034(3) Å, b=19.4505(6) Å, c=8.5188(2) Å, β=102.449(2). Not only were the impedance spectroscopy measurements of (C₅H₁₀N)₂BiBr₅ carried out from 209 Hz to 5 MHz over the temperature range of 318 K–373 K, but also its ac conductivity evaluated. Besides, the dielectric relaxation was examined using the modulus formalism. Actually, the near values of activation energies obtained from the impedance and modulus spectra confirms that the transport is of an ion hopping mechanism, dominated by the motion of the H⁺ ions in the structure of the investigated material.     

Fluorescence and electrochemical recognition of nucleosides and DNA by a novel luminescent bioprobe Eu(III)-TNB

The luminescence arising from lanthanide cations offers several advantages over organic fluorescent molecules: sharp, distinctive emission bands allow for easy resolution between multiple lanthanide signals; long emission lifetimes (μs –ms) make them excellent candidates for time-resolved measurements; and high resistance to photo bleaching allow for long or repeated experiments. A method is presented for determination of nucleosides using the effect of enhancement of fluorescence of the easily accessible europium(III)-TNB in presence of different nucleosides. The latter coordinates to Eu(III) -TNB and enhances its luminescence intensity as a result of the displacement of water from the inner coordination sphere of the central metal. A similar method for the determination of DNA based on the quenching of Eu(III)-TNB has been established. The interaction of Eu(III)-4,4,4 trifluoro-1-(2-naphthyl)1,3-butanedione (TNB) complex with nucleosides (NS) (guanosine, adenosine, cytidine , inosine) and DNA has been studied using normal and time-resolved luminescence techniques. Binding constants were determined at 293 K, 298 K, 303 K, 308 K and 313 K by using Benesi-Hildebrand equation. A thermodynamic analysis showed that the reaction is spontaneous with ΔG being negative. The enthalpy ΔH and the entropy ΔS of reactions were all determined. The formation of binary and ternary complexes of Eu (III) with nucleosides and TNB has been studied potentiometrically at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol.dm⁻³ (KNO₃) . The formation of the 1:1 binary and 1:1:1 ternary complexes are inferred from the corresponding titration curves. Initial estimates of the formation constants of the resulting species and the protonation constants of the different ligands used have been refined with the HYPERQUAD computer program. Electrochemical investigations for the systems under investigations have been carried out using cyclic voltammetry (CV), differential pulse polarography (DPP), and square wave voltammetry (SWV) on a glassy carbon electrode in I = 0.1 mol/L p-toluenesulfonate as supporting electrolyte.     

A New Heterocyclic Multicomponent Reaction For the Combinatorial Synthesis of Fused 3-Aminoimidazoles

When general and reliable , multicomponent reactions are among the most powerful tools in modern drug discovery. The principle of chemical ligation of reactive partners (see reaction scheme) has been employed to find a new, highly efficient synthesis of fused 3-aminoimidazoles.     

Screen-printed electrochemical sensors for label-free potentiometric and impedimetric detection of human serum albumin

Herein, two electrochemical methods based on potentiometric and impedimetric transductions were presented for albumin targeting, employing screen-printed platforms (SPEs) to make easy and cost-effective sensors with good detection merits. The SPEs incorporated ion-to-electron multi-walled carbon nanotubes (MWCNTs) transducer. Sensors were constructed using either tridodecyl methyl-ammonium chloride (TDMACl) (sensor I) or aliquate 336S (sensor II) in plasticized polymeric matrices of carboxylated poly (vinyl chloride) (PVC-COOH). Analytical performances of the sensors were evaluated using the above-mentioned electrochemical techniques. For potentiometric assay, constructed sensors responded to albumin with −81.7 ± 1.7 (r² = 0.9986) and −146.2 ± 2.3 mV/decade (r² = 0.9991) slopes over the linearity range 1.5 μM–1.5 mM with 0.8 and 1.0 μM detection limits for respective TDMAC- and aliquate-based sensors. Interference study showed apparent selectivity for both sensors. Impedimetric assays were performed at pH = 7.5 in 10 mM PBS buffer solution with a 0.02 M [Fe(CN)₆]^−3/−4 redox-active electrolyte. Sensors achieved detection limits of 4.3 × 10⁻⁸ and 1.8 × 10⁻⁷ M over the linear ranges of 5.2×10⁻⁸–1.0×10⁻⁴ M and 1.4×10⁻⁶–1.4×10⁻³ M, with 0.09 ± 0.004 and 0.168 ± 0.009 log Ω/decade slopes for sensors based on TDMAC and aliquate, respectively. These sensors are characterized with simple construction, high sensitivity and selectivity, fast response time, single-use, and cost-effectiveness. The methods were successfully applied to albumin assessment in different biological fluids.