Syntheses, structure and intercalation properties of low-dimensional phenylarsonates, A(HO3AsC6H5)(H2O3AsC6H5) (A = Tl, Na, K and Rb)

Four new low-dimensional phenylarsonates, A(HO₃AsC₆H₅)(H₂O₃AsC₆H₅) (A = Tl(1), Na(2), K(3) and Rb(4)), have been synthesized and characterized by X-ray diffraction, spectroscopic and thermal studies. They crystallize in triclinic unit cells and have approximately planar arrangement of A⁺ ions, coordinated to oxygen atoms of phenylarsonates, on both sides. Structure of thallium phenylarsonate as determined by single crystal X-ray diffraction, is one-dimensional, whereas those of alkalimetal analogues are two-dimensional. Successful intercalation reactions of compounds1 and2 with primaryn-alkyl amines have been demonstrated. Dedicated to Prof J Gopalakrishnan on his 62nd birthday.     

Nucleophile-assisted Pt-catalyzed cyclization of enynones: an access to synthesis of highly substituted furans

A new and efficient Pt-catalyzed hydroxy- or alkoxy cyclization of 2-(1-alkynyl)-2-alkene-1-ones offers a general synthetic pathway to a wide range of highly substituted furans in good to excellent yields.     

Charge transport and discharge mechanism in (PVC+KClO3) polymer electrolyte films

This paper presents results of the studies on ionic conductivity and transference number measurements on potassium chlorate (KClO₃) complexed polyvinyl chloride (PVC) films prepared by solution-cast technique. Temperature dependence of ionic conductivity and transference number data indicated the dominance of ion-type charge transport in these specimens. The magnitude of conductivity increased with increase in the concentration of the salt and temperature. Using this (PVC+KClO₃) electrolyte, solid-state electrochemical cells were fabricated and their discharge profiles were studied under a constant load of 100 kΩ. Several cell profiles associated with these cells were evaluated and are reported.     

Iodine-catalyzed C- and O-nucleophilic substitution reactions of aryl-propargyl methanols

Aryl propargylic methanols undergo C- and O-nucleophilic substitution reactions in the presence of a catalytic amount of iodine in short reaction times with good yields.     

Single crystal EPR and optical studies of paramagnetic ions doped zinc potassium phosphate hexahydrate—Part I: Cu(II)—a case of orthorhombic symmetry

Single crystal electron paramagnetic resonance (EPR) studies on Cu(II) doped zinc potassium phosphate hexahydrate (ZPPH) were carried out at room temperature. The angular variation spectra in the three orthogonal planes indicate that the paramagnetic impurity has entered the lattice substitutionally in place of Zn(II) and the spin Hamiltonian parameters calculated from these spectra are g(xx) = 2.188, g(yy) = 2.032, g(zz) = 2.373, Axx = 50 G, Ayy = 65.0 G and Azz = 80 G. The g and A tensors were coincident and these values matched fairly well with the values obtained from powder spectrum. The bonding parameters have also been calculated.     

Total synthesis of eupomatilones 4 and 6: structurally rearranged and atropisomerically fluxional lignan natural products

[structure: see text] A convergent and diastereocontrolled total synthesis of eupomatilones 4 and 6 is reported and was based on a diastereoselective hydroboration/oxidation sequence and a convergent Lipshutz biarylcuprate cross-coupling reaction. The structure of eupomatilone 6 is revised.     

Total synthesis of antifungal gamahonolide A

The first stereoselective total synthesis of gamahonolide A (1) has been accomplished using aminoxylation, Keck allylation, and ring-closing metathesis (RCM) reactions as key steps.     

Developing Intense Blue and Magenta Colors in α‐LiZnBO3: The Role of 3d‐Metal Substitution and Coordination

We describe the synthesis, crystal structures, and optical absorption spectra/colors of 3d‐transition‐metal‐substituted α‐LiZnBO₃ derivatives: α‐LiZn_1?xM^II_xBO₃ (M^II=Co^II (0<x<0.50), Ni^II (0<x≤0.05), Cu^II (0<x≤0.10)) and α‐Li_1+xZn_1?2xM^III_xBO₃ (M^III=Mn^III (0<x≤0.10), Fe^III (0<x≤0.25)). The crystal structure of the host α‐LiZnBO₃, which is both disordered and distorted with respect to Li and Zn occupancies and coordination geometries, is largely retained in the derivatives, which gives rise to unique colors (blue for Co^II, magenta for Ni^II, violet for Cu^II) that could be of significance for the development of new, inexpensive, and environmentally friendly pigment materials, particularly in the case of the blue pigments. Accordingly, this work identifies distorted tetrahedral MO₄ (M=Co, Ni, Cu) structural units, with a long M?O bond that results in trigonal bipyramidal geometry, as new chromophores for blue, magenta, and violet colors in a α‐LiZnBO₃ host. From the L*a*b* color coordinates, we found that Co‐substituted compounds have an intense blue color that is stronger than that of CoAl₂O₄ and YIn_0.90Mn_0.10O₃. The near‐infrared (NIR) reflectance spectral studies indicate that these compounds exhibit a moderate IR reflectivity that could be significant for applications as “cool pigments”.     

Coordination chemistry of chromium-Salen complexes studied by electrospray ionization mass spectrometry

The gas-phase coordination behavior of the [Cr(III)(Salen)]PF(6) complex at the free axial positions has been studied in the presence of amines as ligands (propylamine and a series of diamines) under electrospray ionization conditions. The [Cr(III)(Salen)](+) complex formed stable five- and six-coordinated complex ions, [Cr(III)(Salen)(L)](+) and [Cr(III)(Salen)(L)(2)](+), respectively, where L = solvent molecule or amine. When diamines were used as ligands, abundant [Cr(III)(Salen)(L)](+) ions were observed in which two axial positions of the [Cr(III)(Salen)](+) species are occupied by the two amino groups of the diamine ligand. The relative abundances of ligated complex ions, fragment ions, and solvent adducts of fragment ions in the ESI mass spectra, were found to depend on the cone voltage used to record the spectrum. The ESI mass spectra of [Cr(III)(Salen)](+) in the presence of diamines as ligands, and experiments on ligand-pickup in the collision cell, clearly demonstrated that the [Cr(III)(Salen)(L)](+) complex ion is stable for 1,2-diaminoethane and 1,3-diaminopropane. The stability of [Cr(III)(Salen)(L)](+) ions gradually decreased from 1,4-diaminobutane to 1,6-diaminohexane, and then showed a slight increase for 1,7-diaminoheptane and 1,8-diaminooctane. The collision-induced dissociation spectra of [Cr(III)(Salen)(L)](+) ions support the above observations.