Syntheses and Structural Investigations of Penta-Coordinated Co(II) Complexes with Bis-Pyrazolo-S-Triazine Pincer Ligands,and Evaluation of Their Antimicrobial and Antioxidant Activities

Two penta-coordinated [Co(^MorphBPT)Cl₂]; 1 and [Co(^PipBPT)Cl₂]; 2 complexes with the bis-pyrazolyl-s-triazine pincer ligands ^MorphBPT and ^PipBPT were synthesized and characterized. Both ^MorphBPT and ^PipBPT act as NNN-tridentate pincer chelates coordinating the Co(II) center with one short Co-N(s-triazine) and two longer Co-N(pyrazole) bonds. The coordination number of Co(II) is five in both complexes, and the geometry around Co(II) ion is a distorted square pyramidal in 1, while 2 shows more distortion. In both complexes, the packing is dominated by Cl…H, C-H…π, and Cl…C (anion-π stacking) interactions in addition to O…H interactions, which are found only in 1. The UV-Vis spectral band at 564 nm was assigned to metal–ligand charge transfer transitions based on TD-DFT calculations. Complexes 1 and 2 showed higher antimicrobial activity compared to the respective free ligand ^MorphBPT and ^PipBPT, which were not active. MIC values indicated that 2 had better activity against S. aureus, B. subtilis, and P. vulgaris than 1. DPPH free radical scavenging assay revealed that all the studied compounds showed weak to moderate antioxidant activity where the nature of the substituent at the s-triazine core has a significant impact on the antioxidant activity.     

One‐Pot Four‐Component Synthesis of Thieno[2,3‐d]pyrimidin‐4‐amines via Sequential Gewald/Cyclocondensation Reactions

A one‐pot four‐component synthesis of thieno[2,3‐d]pyrimidin‐4‐amines via sequential Gewald/cyclocondensation reactions is described. 2‐Aminothiophene‐3‐carbonitriles obtained from the Gewald reaction between cyclic ketones, malononitrile, and sulfur underwent a condensation? cyclization reaction with benzonitriles under solvent‐free conditions to afford the title compounds in excellent yields.     

Solid State Cleavage of Semicarbazones with Cerium Ammonium Nitrate Supported by Wet Alumina

Summary.  Cerium ammonium nitrate on wet alumina rapidly regenerates carbonyl compounds from their corresponding semicarbazone derivatives under solvent-free conditions; the process is expedited by microwave irradiation. Received April 25, 2001. Accepted (revised) July 9, 2001     

Study of urease inhibitory activity by medicinal plants extract based on new catalyst for Berthelot reaction and Taguchi experimental design

The Berthelot reaction is a well-established colorimetric method for determination of ammonia. In this work, the effects of different bivalent ions (Ba²⁺, Cd²⁺, Co²⁺, Cu²⁺, Fe²⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺, and Pb²⁺) were studied as catalyst on the Berthelot reaction efficiency. CuCl₂ was generally found as the best catalyst that provides a rapid and stable blue indophenol color. The Taguchi experimental design methodology has been applied to find optimum conditions. Four factors including temperature, pH, reaction time, and CuCl₂ concentration at five levels were considered to achieve optimum conditions. Blue indophenol color stability for 40 min, and linearity response up to 20 mM of ammonium sulfate were achieved by further validation experiments. Limit of detection and quantification for this approach was 0.15 and 0.5 mM, respectively. Inhibitory activity of three traditional medicinal plants extract (Citrus aurantifolia, Laurus nobilis, and Zingiber officinale) was evaluated against jack bean urease activity by Berthelot reaction in the presence of CuCl₂ as catalyst, and results were compared with traditional Berthelot reaction.     

Micro-cloud point extraction for preconcentration of Aspirin in commercial tablets prior to spectrophotometric determination

A fast, simple, inexpensive and effective method is developed for spectrophotometric determination of Aspirin in commercial tablets based on micro-cloud point extraction (MCPE). The proposed MCPE is essentially a miniaturized form of traditional cloud point extraction (CPE) in which only a few microliters of micellar extracting phase is sufficient for spectrophotometric determination. For comparison with MCPE, cloud point extraction was examined for Aspirin extraction. Triton X-114 was employed as a non-ionic surfactant for extraction/preconcentration of aspirin. Factors influencing the extraction efficiency, such as concentration of Triton, effect of pH, type of dilution solvent, etc. were investigated and optimized. Under the optimized condition, linear calibration curve for MCPE was in the range of 0.05–2 mg/L and limit of detection of 0.05 mg/L was obtained, whereas linear part for CPE calibration curve was 0.9 to 11 mg/L with a limit of detection of 0.5 mg/L.     

Molecularly imprinted stir bar sorptive extraction coupled with high-performance liquid chromatography for trace analysis of naphthalene sulfonates in seawater

In this paper, a novel molecularly imprinted polymer coated stir bar has been used to selectively extract naphthalene sulfonates (NS_s) directly from seawater sample. 1-Naphthalene sulfonic acid (1-NS) was used as template molecule. The effects of different parameters were optimized on the extraction efficiency and the optimum conditions were established as: the absorption and desorption times were fixed, respectively, at 10 and 15 min, stirring speed was 700 rpm, pH was adjusted to 4.1, amount of NaCl was 1 mol L^?1 and extraction process was performed at a temperature of 50 °C. The linear ranges were 2–250 µg L^?1 for 3,6-NDS-1-OH (1-naphthol-3,6-disulfonic acid), 4–250 µg L^?1 for 2-NS (2-naphthalene sulfonate) and 3–250 µg L^?1 for 1-NS. The detection limits were within the range of 0.32–0.95 µg L^?1. Under optimum conditions, the detection limits of the NSs were 0.84, 0.95 and 0.32 µg L^?1 with the enrichment factor of 117-, 41- and 77-fold for 2-NS, 1-NS, and 6-NDS-1-OH, respectively. The repeatability of the method was satisfactory (0.53 ≤ RSD ≤6.0 %, n = 10). The method has been successfully applied for the analysis of trace amounts of three naphthalene sulfonates in seawater of Chabahar Bay.     

Novel and facile methods for the synthesis of DTPA-mono-amide: a new completely revised strategy in radiopharmaceutical chemistry

DTPA is a very strong metal chelator widely utilized in radiopharmaceutical chemistry for conjugation of chemicals which do not have enough potency for direct metalo-labeling and also to manage toxic radioactive materials such as plutonium, americium, and curium. It is difficult to conjugate DTPA to an amine group in a singular direction and such reactions usually also coincidently produce a mixture of DTPA-bis-amides and DTPA-mono-amide resulting in considerable insufficiencies/difficulties in synthesis and especially yield/separation procedures. In this paper, novel methods for the exclusive synthesis of DTPA-mono-amide have been established which extensively reduce the difficulties otherwise encountered and increase the reaction’s yield considering the green chemistry approaches. This is expected to be of interest to radiopharmaceutical researchers interested in the DTPA (Radio)-metallic-conjugate. Overall, this paper provides a framework to achieve a higher degree of propriety from DTPA as a chelator to conjugate to the chemical compounds.     

Synthesis, X-ray structure and anti-corrosion activity of two silver(I) pyrazino complexes

Two new silver(I) pyrazine complexes [Ag₂(ampyz)(NO₃)₂]_n, 1 and {[Ag(2,3-pyzdic)](NO₃)}_n, 2 (where ampyz = aminopyrazine, and 2,3-pyzdic = 2,3-pyrazinedicarboxamide) were synthesized and structurally characterized by X-ray single crystal structure analysis. Complex 1 has a 2D sheet structure through both bridging μ_O,O′-(NO₃) groups and μ_N,N′-pyrazine moieties. A 3D structure with a characteristic (10,3)-d or 10³-utp net is formed through extensive hydrogen bonding. Complex 2 has a 1D chain structure through bridging μ_N,N′-pyrazine moieties. Strong hydrogen bonds further connect these chains to extend the dimensionality to a 3D network structure. The complexes were tested as corrosion inhibitors for mild steel in 0.1 M nitric acid medium using potentiodynamic polarization technique. Both complexes are of mixed type corrosion inhibitors with dominant anodic effect. The inhibition efficiencies are 68% and 50% for complexes 1 and 2, respectively. The inhibition mechanisms of both inhibitors are mainly due to adsorption of the inhibitor molecules on the surface of mild steel. All data were compared and fitted to the kinetic-thermodynamic model. The binding constants K are 3263 and 1147 for complexes 1 and 2, respectively.     

Bis(1,3,5‐triazine‐2,4,6‐triamine‐κN1)silver(I) nitrate

The title compound, [Ag(C₃H₆N₆)₂]NO₃, has an alternating two‐dimensional bilayer structure supported by extensive hydrogen bonds. The [Ag(melamine)₂]⁺ cationic monomers (melamine is 1,3,5‐triazine‐2,4,6‐triamine) are connected via N—H...N hydrogen bonds to form two‐dimensional sheets. Nitrate groups are sandwiched between two sheets through N—H...O hydrogen bonds. An almost perfectly linear coordination geometry is found for the Ag^I ions. The triazine ligands are slightly distorted due to π–π interactions.     

Purification of inductors and improvement of phase noise in monolithic differential LC-VCOs

A novel idea for the improvement of phase noise in differential LC-VCOs with no degradation of power consumption is proposed. Being based on purification of inductors to enhance the quality factor (Q), the application of the idea in design of CMOS based Giga Hertz (GHz) range low power and low phase noise monolithic differential LC-VCOs is illustrated and analyzed. Post-layout simulations using CMOS 0.18 μm TSMC RF design kit are used for evaluation.