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The crystal structure of the high-pressure phase of potassium hydrogen carbonate, here termed KHC[O.sub.3] form III, has been solved using single-crystal X-ray diffraction techniques. It adopts triclinic P[bar.1] symmetry and is formed on direct compression of the monoclinic ambient-pressure phase (kalicinite, form I) via a first-order phase transition at 3.2 GPa ([DELTA]V]/V ~4%). We have also used time-of-flight high-pressure neutron powder-diffraction to determine the structural changes in KDC[O.sub.3] of the form I and III polymorphs to 8.3 GPa. This study indicates that the transition appears to be in response to pronounced displacements of the [K.sub.+] cations and the cooperative tilting of the [(DC[O.sub.[bar.3]).sub.2] dimers. The O ... O hydrogen bond distance shows a monotonic compression over the entire pressure range studied with no obvious discontinuity at the phase transition. However, the O-D ... O bond angle appears to exhibit an abrupt ~4[degrees] decrease across the I-III phase transition with a concomitant change in its pressure dependence. Birch Murnaghan fits to the equation of state data above and below the transition indicate that form III [[B.sub.0] = 26.5(2.8) GPa, B' = 5.2(6)] is marginally less compressible than form I [[B.sub.0] = 22.7(8) GPa, B'= 4.1(5)]. Keywords: Kalicinite, high-pressure, crystal structure, phase transition

The circular dichroism spectroscopy, differential scanning calorimetry and singular-value decomposition are used to assess the number of species present in the dissociation process. The results indicate that three species exist in equilibria during the melting process and a model is presented for the heat-induced denaturation from the folded to the unfolded state.

The crystal growth and structural characterization of the new palladates LnKPd[O.sub.3] (Ln = La, Pr, Nd, Sm-Gd) and the partially copper-substituted analogue, PrK([Cu.sub.0.14][Pd.sub.0.86])[O.sub.3], are presented. The results have shown that the materials are all isostructural and have ordered slabs of Ln[O.sub.7]- and K[O.sub.7]-capped trigonal prisms and isolated Pd[O.sub.4] square planes.

The unliganded and liganded, with coactetyl A (CoA) and with [K.sup.+] structures of human mitochondrial recombinant tetrameric thiolase, T2 are described and effect of potassium ions on the structure is examined. The crystal structure shows that each T2 subunit has a binding site for chloride ion and potassium ion and each of these ion-binding sites is defined by loops at the active site, which results in the stabilization of the catalytic loops.

Substituted N-alkylazinium salts are used to add perfluoroisopropyl carbanions generated in situ from hexafluoropropene and solid potassium fluoride in order to obtain perfluoroalkyl-substituted dihydro derivatives, which are readily oxidized. The scope and limitations of this novel and useful synthesis of perfluoroalkylated heterocycles are discussed.

The first synthesis of potassium orthoselenate(VI), [K.sub.6](Se[O.sub.4])(Se[O.sub.5]), and the structure determination from synchrotron powder diffraction data is reported. Selenium has displayed two different complex anions, tetrahedral Se[O.sub.4.sup.2-] and trigonal-bipyramidal Se[O.sub.5.sup.4-].

The compounds K0.91U1.79S6 and KU2Se6, members of the AAn2Q6 actinide family, are synthesized from US2, K2S and S at 1273 K and U, K2Se and Se at 1173 K, respectively. Ku2Se6 shows Curie-Weiss behavior above 30 K and no magnetic ordering down to 5 K and both K0.91U1.79S6 and KU2Se6 crystallize in space group Immm of the orthorhombic system.

A new complex (1) of Prussian blue analogue with the composition of K(sub 0.2)Mn(sub 1.4)Cr(CN)(sub 6)-6H(sub 2)O was prepared and characterized structurally and magnetically. The results show that complex is a ferrimagnet with T(sub c)= 66K and its magnetic behavior can be modulated through a dehydration/rehydration treatment and the T(sub c) value can be restored after rehydration.

The experimental study of the photolytic reactivity on 18-diazo-1,4,7,10,13,16-hexaoxacyclononadeca-17,19-dione and its potassium and sodium complexes is discussed. It is seen that the triplet-sensitized photolysis of diazomalonates produces 2,4-dioxo-19-crown-6 that is apparently formed through the triplet state of the intervening carbene.

The mixed-valence double salt K3(MnO4)(sub 2) crystallizes in space group P2(sub 1)/m with Z=2. The results of the polarized neutron diffraction study of K3 (MnO4)(sub 2) are discussed.

The electronic properties of the ternary potassium-ammonium graphite intercalation compound K(NH3)(sub 4)C24 are studied using generalized gradient-corrected density functional theory. This results in the K 4s electron being promoted to a very diffuse state extending in the outer region of the K(NH3)4 cluster, with the electron only loosely bound to the nearly planar K(NH3)(sub 4)(super +) system.

The report stated that supramolecular cation structures of (NH(sub 4)(super +)) (crown ethers and (NH(sub 2)(super -)) NH(sub 3)(super +)) (crown ethers were incorporated into partially charge-transferred electrically conducting [Ni(dmit)(sub 2)] salts. The large and flexible [18] crown-6 allowed for maintaining the same ionic channel structure through replacement of the NH(sub 4)(super +) cation by NH(sub 2)-NH (sub 3)(super +).

A mixed potassium-lanthanide wheel-shaped-structured, hexanuclear coordination oligomer and an octanuclear coordination polymer are presented. All presented compounds are obtained in moderate yields in a one-pot procedure.

The electronic structure of K3Bi2 is discussed on the basis of first-principles density functional theory (DFT) calculations. Only the valence electrons are considered in the calculation, with the core being replaced by norm-conserving scalar relativistic pseudopotentials factorized in the Kleinman-Bylander form.

An epitaxial growth technique is applied in order to improve the uniaxial magnetic anisotropy K(sub u)(super grain) of c-plane-oriented columnar grains for CoCr-based perpendicular recording media. It is observed that in the media with a high concentration of B or Cr, the thermal stability was improved mainly due to an increase of K(sub u)(super grain) rather than an enlargement of activation volume (V (sub act)).

The structures of [K.sub.2][([H.sub.2]O).sub.2][B.sub.12][F.sub.12] and [K.sub.2][([H.sub.2]O).sub.4][B.sub.12][F.sub.12] are determined by using X-ray diffraction. The rates of absorption and desorption of [H.sub.2]O from unit cells at the surface of the microcrystals and the rate of diffusion of [H.sub.2]O across the moving [K.sub.2][([H.sub.2]O).sub.2][B.sub.12][F.sub.12(s)]/[K.sub.2][B.sub.12][F.sub.12(s)] phase boundary, are faster than the fastest rates of change in sample mass due to hydration and dehydration.

The article explains the synthesis, structure and the hydrogen release features of the newly developed potassium(I) amidotrihydroborate complex. The application of the compound as a new hydrogen storing material is also explained.

Several studies are conducted to explain the various effects of period, as well as amplitude of microwaviness as exhibited on the laser induced damage threshold of the [KH.sub.2][PO.sub.4] crystals.

The effect of L-threonine (LT) doping on crystalline perfection, second harmonic generation (SHG) efficiency, optical transparency, and laser damage threshold (LDT) in potassium dihydrogen phosphate (KDP) crystals grown by slow evaporation solution technique (SEST) is examined. Powder x-ray diffraction data has confirmed the crystal structure of KDP and has displayed a systematic variation in intensity of diffraction peaks in correlation with morphology due to varying LT concentration.

The nucleation limited switching model is employed to explain the ferroelectric polarization switching of the different ferroelectric [(N[H.sub.4]).sub.0.39][K.sub.0.61]N[O.sub.3] films.

The problem of finding phase-matching directions in noncentrosymmetric biaxial crystals is simplified by using conoscopic interferometry. The studies have shown that the method for the particular case of a biaxial KTiOP[O.sub.4] crystal, where it is suitable for finding the optimum-phase-matching directions.

The X-ray diffraction studies are conducted to explain the synthesis, structure and properties of the intermetallic compound, [K.sub.23][Au.sub.12][Sn.sub.9]. The open bond features and the electronic structure of the complex are also discussed.

The article explains the synthesis, as well as the properties of the mixed-valent palladate K[Pd.sub.2][O.sub.3] compound. The alternate sequencing and ordering of the [Pd.sup.2+] and [Pd.sup.4+] compounds present in the complex is also discussed.

The treatment of oxazolidinone carboxylic acid with potassium carbonate has produced olefin by a double decarboxylation reaction. 15,16-Normaltrexone derivative prepared from double decarboxylation product has displayed strong affinity for the [mu] opioid receptor, showing it to be a new opioid lead compound.

A study is conducted to examine the dielectric, ferroelectric, piezoelectric, and electrostrictive properties of [K.sub.0.5][Na.sub.0.5]Nb[O.sub.3] single crystals synthesized by solid-state crystal growth. The extremely high [M.sub.33] value for the crystals is explained by the extrinsic strain from the domain-wall motion and by comparing the properties of the surrounding polycrystalline KNN ceramic.

The preparation of novel cis-1,2-fused 1,3-oxathiolan-, 1,3-oxaselenolan-, and 1,3-oxazolidin-2-imine carbohydrate derivatives is carried out by treatment of corresponding 1,2-anhydrosugars with potassium thiocyanate, potassium selenocyanate, and sodium cyanamide, respectively. The procedure is found to be compatible with several protecting groups such as acyl, benzyl, and silyl as well as sugars of different configurations.

The methods for the deprotection of pinanediol and pinacol esters of various boronic acids assessed via fluoroborane intermediates are reported. Procedures for transformation of both trifluoroborates and difluoroboranes to free boronic acids are also described.

The preparation of a bench-stable potassium trifluoroborate enol ether reagent is presented. The reagent is found to be suitable for the incorporation of 2,2-difluoroenolethers into aryl and heteroaryl systems via palladium-mediated cross-coupling with suitable halide coupling partners.

A general method is developed for in situ trapping of arylmetal intermediates by halogen, sulfur, ketone and aldehyde electrophiles, which has produced the functionalization of the most acidic position in arene. [K.sub.3]P[O.sub.4] base is used for functionalizing pentafluorobenzene, benzothiazole and benzoxazole.

Activated and deactivated aryl and heteroaryl chlorides are cross-coupled with potassium vinyl- and alkenyltrifluoroborates by using 4-hydroxyacetophenone oxime derived palladacycle as precatalyst in Pd loading, binap as ligand, and [Cs.sub.2]C[O.sub.3] as base in dimethylformamide (DMF). The corresponding cross-coupled compounds, such as styrenes, stilbenes and alkenylarenes, are obtained with high regio- and diastereoselectivity.

One mol % Pd loading of 4-hydroxyacetophenone oxime derived palladacycle or Pd[(OAc).sub.2] as precatalysts, [K.sub.2]C[O.sub.3] as base and water as additive was used to cross-couple potassium vinyl and alkenyltrifluoroborates with aryl and heteroaryl bromides to yield styrenes, stilbenoids, and alkneylbenzenes. These simple phosphine-free reaction conditions facilitate the palladium recycling from the aqueous phase during up to five runs by extractive separation of the products, which contain 58-105 ppm of Pd.