Interlayer interaction of two-dimensional layered spin crossover complexes [FeIIH3L(Me)][FeIIL(Me)]X (X-=ClO4-, BF4-, PF6-, AsF6-, and SbF6-; H3L(Me)=tris[2-(((2-methylimidazol-4-yl)methylidene)amino)ethyl]amine)

A series of two-dimensional (2D) spin crossover complexes, [FeIIH3L(Me)][FeIIL(Me)]X (X-=ClO4-, BF4-, PF6-, AsF6-, SbF6-) 1-5, have been synthesized, where H3L(Me) denotes an hexadentate N6 tripodlike ligand containing three imidazole groups, tris[2-(((2-methylimidazol-4-yl)methylidene)amino)ethyl]amine. Compounds 1-5 exhibit a two-step (HS-[FeIIH3L(Me)](2+) + HS-[FeIIL(Me)]-) <--> (HS-[FeIIH3L(Me)](2+) + LS-[FeIIL(Me)]-) <--> (LS-[FeIIH3L(Me)](2+) + LS-[FeIIL(Me)]-) spin-transition. The crystal structure of [FeIIH3L(Me)][FeIIL(Me)]PF6 (3) was determined at 295, 200, and 100 K. The structure consists of homochiral extended 2D puckered sheets, in which the complementary [FeIIH3L(Me)](2+) and [FeIIL(Me)]- capped tripodlike components, linked together by imidazole-imidazolate hydrogen bonds, are alternately arrayed in an up-and-down mode. The Fe-N bond distances and angles revealed that the FeII sites of both constituting units are in the high-spin (HS) state at 295 K; at 200 K, the FeII sites of [FeIIH3L(Me)](2+) and [FeIIL(Me)]- are in the HS and low-spin (LS) states, respectively. The FeII sites of both constituting units are in the LS state at 100 K. The size of the counteranion affects significantly the intra- and interlayer interactions leading to modifications of the spin crossover behavior. The onset of the second spin-transition of the ClO4- (1) and BF4- (2) salts adjoins the first spin-transition, while a mixed (HS-[FeIIH3L(Me)](2+) + LS-[FeIIL(Me)]-) spin-state spans a temperature range as wide as 70 K for salts 3-5 with larger counteranions, PF6-, AsF6-, and SbF6-, respectively. Compounds 1 and 2 showed remarkable LIESST (light induced excited spin state trapping) and reverse-LIESST effects, whereas 3-5 showed no remarkable LIESST effect. The interlayer interaction due to the size of the counteranion is an important factor governing the spin crossover behavior and LIESST effect.     

Heat of Formation for LiMyMn2−yO4 (M=Co,Cr, Li,Mg, Ni) Spinel Solid Solution

The enthalpy of formation for LiM_yMn_2–yO₄ (M=Co, Cr, Li, Mg, Ni) was measured by a Tian-Calvet type high temperature isothermal microcalorimeter. The standard enthalpy of formation for LiMn₂O₄ at 876 K was evaluated to be H_f⁰=–1404.2±6.4 kJ mol^–1. The partial substitution of Co and Ni for Mn decreased the absolute H_f⁰ value, while that of Cr and Mg for Mn increased the absolute H_f⁰ value. In the case of the partial substitution of Li for Mn, no marked change in H_f⁰ could be observed.This revised version was published online in November 2005 with corrections to the Cover Date.     

Homochiral column structure of rac- and lambda-tris(ethylenediamine)cobalt(III) cyclotriphosphate dihydrate in crystal structures and cation-anion association in aqueous solution

rac- and Lambda-tris(ethylenediamine)cobalt(III) cyclotriphosphate dihydrate with the chemical formulas rac-[Co(en)(3)]P(3)O(9).2H(2)O (1) and Lambda-[Co(en)(3)]P(3)O(9).2H(2)O (2) were synthesized, and their crystal structures were determined by single-crystal X-ray analyses. In 1, the cationic complex molecule [Co(en)(3)](3+) with the Delta or Lambda enantiomer and cyclotriphosphate anion are alternately arrayed and connected by multiple hydrogen bonds to form a homochiral column structure. Adjacent homochiral columns with different chirality for 1 are connected by intercolumn hydrogen bonds through P(3)O(9)(3)(-) anions, as the bridging groups, to form a tetrameric cyclic cylindrical structure, while the adjacent columns with the same chirality are connected for 2 to form the cyclic cylindrical structure. All 6 amino groups per [Co(en)(3)](3+) participate in the formation of 12 hydrogen bonds, in which 8 hydrogen bonds contribute to the construction of a homochiral column and the remaining 4 hydrogen bonds contribute to the intercolumn interactions. The circular dichroism spectrum of the aqueous solution of Lambda-[Co(en)(3)](3+) changes drastically when excess P(3)O(9)(3)(-) is added, and this change is explained by ion-pair formation. The thermodynamic association constant of [Co(en)(3)](3+) with P(3)O(9)(3)(-), calculated from the conductivity data, was log K = 4.26 at 25 degrees C.     

Three-dimensional fermi-liquid ground state in the quasi-one-dimensional cuprate PrBa(2)Cu(4)O(8)

The interchain resistivity of PrBa(2)Cu(4)O(8) has been measured in high magnetic fields up to 30 T. Co-herent interchain transport at low temperatures is destroyed by a large magnetic field applied perpendicular to the CuO chains. Comparisons with quasiclassical transport theory provide strong experimental support for a three-dimensional Fermi-liquid ground state in PrBa(2)Cu(4)O(8), despite extreme anisotropy in its electronic properties and the presence of strong electron correlations.     

Operational modes for transient isotachophoretic preconcentration-capillary zone electrophoresis and detectable concentration of rare earth ions.

Operational modes for transient isotachophoretic preconcentration capillary zone electrophoresis (tr-ITP-CZE) were studied by using 5 microM and 0.5 microM rare earth mixtures as analytes in comparison with field-enhanced sample stacking. After examination of several operational modes for tr-ITP, it was found that tr-ITP effectively occured even if both the leading electrolyte and the terminating electrolyte were injected after the sample plug. This was explained as the result of a field-enhanced stacking for both sample components and the leading and terminating ions. The observed theoretical plate numbers were 4-20 times higher than those obtained by normal stacking; and the estimated low limit of detectable concentration of rare-earth elements (REE) was ca. 0.1 microM which was 2.5 times lower compared to normal stacking. For the 0.5 microM sample, a concentration factor of 20 000 could be achieved after only tr-ITP.     

Isotachophoretic separation behavior of rare-earth EDTA chelates and analysis of minor rare-earth elements in an iron ore by bidirectional isotachophoresis-particle-induced X-ray emission.

Mobilities of 16 anions of rare-earth-EDTA 1:1 chelate (RE-EDTAs) were isotachophoretically measured by using two leading electrolytes (pH 3.6 and 6.0) in order to assess their separation behavior. The leading electrolyte was 20 mM hydrochloric acid. The pH of the solution was adjusted to 3.6 by adding beta-alanine and to 6.0 by adding histidine. The obtained mobilities were very close to each other in the range 20.1x10(-5)-21.9x10(-5) cm2 V(-1) s(-1) with the minimum mobilities for Pr-EDTA and Nd-EDTA for pH 3.6 and 6.0, respectively, and pH dependence was hardly observed. On the basis of the above knowledge. minor rare-earth elements in a standard iron ore sample were determined as RE-EDTAs by bidirectional isotachophoresis-particle-induced X-ray emission (PIXE), where the Fe(II) matrix digested by alkali fusion was separated as Fe(II)Phen3(2+) (phen = 1,10-phenanthroline). Since 5% of the total iron was still detected as Fe(III)EDTA- and might disturb PIXE analysis of RE-EDTA-, itaconic acid was used as the spacer for Fe(III)EDTA- and RE-EDTA-. The fractions of RE-EDTA- were successfully analyzed off-line by a multielemental analytical method, PIXE [analytical result (3.62% (w/w) as RE2O3]; the nominal value was 3.37% (w/w) as RExOy.     

Factors affecting antibiotic production in bioreactors with immobilized algal cells

Applied Biochemistry and Biotechnology - A fresh-water, nitrogen-fixing blue-green alga (cyanobacterium),Scytonema sp. No. 11 (TISTR 8208), was isolated from a paddy field in northern Thailand....     

Structural stability in partially substituted lithium manganese spinel oxide cathode

LiMn₂O₄ is one of the most promising cathode materials for lithium secondary battery because of natural abundance of manganese in the crust and its low toxicity to environment. Lithium ion can almost reversibly intercalate into or deintercalate from lithium manganese spinel oxide LiMn₂O₄. A part of substitution of manganese with other transition metals brings the improvement of cycle life. We focused on the local structure of the spinels and considered the effect of the local distortion on the cycle life of the spinel cathodes. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.