Versatile binding properties of a di-2-pyridyl ketone nicotinoylhydrazone ligand: crystal structure of a Cu(II) complex

Six new copper complexes of di-2-pyridyl ketone nicotinoylhydrazone (HDKN) have been synthesized. The complexes have been characterized by a variety of spectroscopic techniques and the structure of [Cu(DKN)(2)]·H(2)O has been determined by single crystal X-ray diffraction. The compound [Cu(DKN)(2)]·H(2)O crystallized in the monoclinic space group P2(1) and has a distorted octahedral geometry. The IR spectra revealed the presence of variable modes of chelation for the investigated ligand. The EPR spectra of compounds [Cu(2)(DKN)(2)(μ-N(3))(2)] and [Cu(2)(DKN)(2)(μ-NCS)(2)] in polycrystalline state suggest a dimeric structure as they exhibited a half field signal, which indicate the presence of a weak interaction between two Cu(II) ions in these complexes.     

Polyvinyl pyrrolidone/Mg(ClO4)2 solid polymer electrolyte: structural and electrical studies

Polymer electrolytes comprising polyvinyl pyrrolidone (PVP) as host polymer and Mg(ClO₄)₂ as dopant salt have been prepared by solution casting technique using double-distilled water as solvent. The changes in the structural properties on the incorporation of dopant were investigated by XRD and FTIR analysis. The ionic conductivity and dielectric behavior were explored using AC impedance spectroscopy. The ionic conductivity increases with increasing dopant concentration. The conductivity enhancement with the increasing salt concentration is correlated with the increase in amorphous nature of the electrolytes. The frequency dependence of electrical conductivity obeys the universal Jonscher power law. The electrical modulus representation shows a loss feature in the imaginary component. The distribution of relaxation times was indicated by a deformed arc form of the Argand plot. The relative dielectric constant (ε _r ) decreases with increase in frequency in the low frequency region whereas a frequency-independent behavior is observed in the high frequency region. The total ionic transference number studies have confirmed that the mobile charge carriers are ions. Results obtained by cyclic voltammetry on SS/60 mol% PVP/40 mol% Mg(ClO₄)₂ SPE/SS symmetrical cell show evidence for reversibility.

     

Friedel-Crafts alkylation of a cage enone: synthesis of aralkyl substituted tetracyclo[5.3.1.0.0]undeca-9,11-diones and the formation of fascinating novel cage compounds with pyrrole and thiophene using Montmorillonite K-10

The intrinsic catalytic properties of Montmorillonite K-10 clay have been utilized for Friedel-Crafts alkylation of the polycyclic caged enone 1 using different carbo and heterocyclic aromatic systems leading to novel compounds. Carbon-carbon bond formation between the aromatic compounds and the cage system has led to three different types of products.     

Curcuma ecalcarata – new natural source of pinocembrin and piperitenone

Phytochemical analysis of the rhizome extract of Curcuma ecalcarata, a hitherto uninvestigated south Western Ghats endemic species, resulted in the isolation and identification of the diaryl heptanoid trans, trans-1,7-diphenyl-5-hydroxy-4,6-heptadiene-3-one (1), steroid β-sitosterol (2), flavanone pinocembrin (4) and monoterpenoids piperitenone (3) and 8-hydroxy piperitone (5). HPTLC estimation of pinocembrin in the rhizome revealed the plant as a rich source of pinocembrin (0.37% dry wt.). The rhizome essential oil was isolated by hydrodistillation and analysed by GC–FID, GC–MS and ¹³C NMR. Among the 30 constituents identified in the oil, monoterpenoids predominated (94.2%) followed by sesquiterpenoids (5.8%). The major compound consisting of 65.2% of the oil was isolated and identified as piperitenone (3). The study highlights the plant as a rich source of the flavanone pinocembrin and the volatile aroma compound piperitenone.     

Isolation and Identification of α-Glucosidase and Protein Glycation Inhibitors from Stereospermum colais

Stereospermum colais (family Bignoniaceae) is a well-known pharmacologically potent medicinal plant reported in traditional systems of medicine. Phytochemical investigation of the roots of S. colais resulted in the isolation of seven compounds, and the metabolites were screened for its α-glucosidase enzyme inhibition and anti-glycation property. The compounds identified were β-sitosterol (1), 2-(4′-hydroxyphenyl) ethyl undecanoate (2), 2-(4′-hydroxyphenyl)ethyl pentadecanoate (3), 5α-ergosta-7,22-dien-3β-ol (4), ursolic acid (5), lapachol (6), and pinoresinol (7). Ursolic acid, lapachol, and pinoresinol possessed IC₅₀ values of 119.01, 130.29, and 125.62 nM, respectively, compared to standard ascorbic acid with an IC₅₀ value of 201.01 nM. The other compounds failed to show the activity. Results of the current study showcased the possible exploration of this medicinal plant for the treatment of type 2 diabetes in line with the development of phytopharmaceutical industry.     

Multiferroic properties of nanocrystalline BaTiO3

Some of the Multiferroics [H. Schmid, Ferroelectrics 162 (1994) 317] form a rare class of materials that exhibit magneto–electric coupling arising from the coexistence of ferromagnetism and ferroelectricity, with potential for many technological applications [J.F. Scott, Nat. Mater. 6 (2007) 256; N.A. Spaldin, M. Fiebig, Science 309 (2005) 391]. Over the last decade, an active research on multiferroics has resulted in the identification of a few routes that lead to multiferroicity in bulk materials [C. Ederer, N.A. Spaldin, Nat. Mater. 3 (2004) 849; D.V. Efremov, J. van den Brink, D.I. Khomskii, Nat. Mater. 3 (2004) 853; N. Hur, S. Park, P.A. Sharma, J.S. Ahn, S. Guha, S.W. Cheong, Nature 429 (2004) 392]. While ferroelectricity in a classic ferroelectric such as BaTiO₃ is expected to diminish with the reducing particle size, [C.H. Ahn, K.M. Rabe, J.M. Triscone, Science 303 (2004) 488; J. Junquera, P. Ghosez, Nature 422 (2003) 506] ferromagnetism cannot occur in its bulk form [N.A. Hill, J. Phys. Chem. B 104 (2000) 6694]. Here, we use a combination of experiment and first-principles simulations to demonstrate that multiferroic nature emerges in intermediate size nanocrystalline BaTiO₃, ferromagnetism arising from the oxygen vacancies at the surface and ferroelectricity from the core. A strong coupling between a surface polar phonon and spin is shown to result in a magnetocapacitance effect observed at room temperature, which can open up possibilities of new electro–magneto-mechanical devices at the nano-scale.     

Synthesis and spectral investigations of vanadium(IV/V) complexes derived from an ONS donor thiosemicarbazone ligand

Four oxovanadium and one dioxovanadium complex with 2-hydroxyacetophenone N(4)-phenylthiosemicarbazone (H₂L) which are represented as [VOLphen]·2H₂O (1), [VOLbipy] (2), [VOLdmbipy] (3), [VOL]₂ (4) and [VO₂HL]·CH₃OH (5) have been synthesized and characterized by elemental analyses, electronic, infrared and EPR spectral techniques. In all the complexes 1–4 the ligand coordinates through phenolic oxygen, azomethine nitrogen and thiolate sulfur. But in complex [VO₂HL]·CH₃OH, coordination takes place in thione form instead of thiolate sulfur. All the complexes except [VO₂HL]·CH₃OH are EPR active due to the presence of an unpaired electron. In frozen DMF at 77 K, all the oxovanadium(IV) complexes show axial anisotropy with two sets of eight line patterns.