K2PdCl4 catalyzed efficient multicomponent synthesis of α-aminonitriles in aqueous media

An efficient, mild and environmentally friendly method has been developed for the Strecker reaction to synthesize α-aminonitriles in the presence of K₂PdCl₄ as a catalyst. The three-component one-pot condensation of an aldehyde, amine and trimethylsilyl cyanide proceeded smoothly in water to afford the corresponding product in high yield with short reaction times.     

Surface plasmon resonance in nano-gold antimony glass–ceramic dichroic nanocomposites: One-step synthesis and enhanced fluorescence application

A single-step melt-quench in situ thermochemical reduction technique has been used to synthesize a new series of Au° nanoparticles embedded antimony glass–ceramic (K₂O–B₂O₃–Sb₂O₃–ZnO) dichroic nanocomposites. X-ray and selected area electron diffractions manifest growth of Au° nanoparticles along (2 0 0) planes. The particle sizes obtained from X-ray diffraction patterns are found to vary in the range 4–21 nm. Dichroic behavior is attributed to the elliptical shape gold nanoparticles having aspect ratio 1.2, as observed from the transmission electron microscopy (TEM) images. The Au° nanoparticles exhibit surface plasmon resonance band (SPR) around 600 nm, which experiences red-shifts with increasing Au concentration. These nanocomposites when co-doped with Sm₂O₃ and excited at 949 nm, exhibit 2-fold intensification of 636 nm red emission transition (⁴G_5/2 → ⁶H_9/2) due to SPR induced local field enhancement of Au° nanoparticles and are promising materials for display applications.     

Rhenium part XV. Tetragonal complexes of nickel(II) containing coordinated perrhenate [ReO4]−

Summary The compounds Ni(NH₃)4(ReO₄)₂ and Ni(py)₄(ReO₄)₂ prepared by reacting Ni(ReO₄)₂ with aqueous ammonia or pyridine, when heated at 150° give Ni(NH₃)₂(ReO₄)₂ and Ni(py)₂(ReO₄)₂ respectively. The kinetics of the thermal decomposition of Ni(NH₃)₂(ReO₄)₂ has been studied. I.r., Raman and electronic spectra, x-ray powder diffraction and magnetic susceptibility measurements (at different temperatures) of the four compounds indicate that they are tetragonal complexes of Ni^II containing coordinated perrhenate.     

Homo and heteronuclear complexes of dioxime ligands

The mononuclear fragments [Cu(HDopn)(OH)2]+ and [Cu(HPopn)(OH)2]+, [H2Dopn=3,3-(trimethylene- dinitrilo)-dibutan-2–one dioximate and H2Popn, = 3, 3-(phenylenedinitrilo)-dibutan-2–one dioximate] were used to prepare four binuclear complexes [(OH2)Cu (Dopn)Cu(ditn)]2+, [(OH2)Cu(Dopn)Ni(ditn)(H2O)]2+ (ditn=diethylenetriamine) and [(OH2)Cu(Popn)Cu(L) (H2O)]2+ (L=2,2-bipyridine or 1,10–phenanthroline). Two trinuclear complexes, [{Cu(Popn)(OH2)}2M (H2O)n]2+ (when M=CuII, n=1; M=ZnII, n= 2), have been synthesised and characterised by elemental analyses, f.a.b. mass, i.r., electronic, e.s.r. spectroscopy and variable temperature (5–300K) magnetic susceptibility measurements. A strong antiferromagnetic interaction (J=–545cm–1 to –700cm–1) has been found for the binuclear copper(II) complexes. The X-band e.s.r. spectra of these complexes at 300K and for trinuclear complexes at 120K indicate square-pyramidal geometry for the copper centres with a (dx2–y2)1 ground state. The binuclear complex of copper(II)–nickel(II) centres with antiferromagnetic interaction (J=–107 cm–1) is described, and moderately strong zero-field splitting within the quartet state leads to Kramers doublet, as indicated by X-band e.s.r. spectra of this complex. The trinuclear copper(II) complex with an antiferromagnetic interaction (J= –350cm–1) is also described. The heterometallic trinuclear copper(II)–zinc(II)–copper(II) system shows a very weak interaction (J–1cm–1).     

Concise syntheses of (+)- and (−)-methylenolactocins and phaseolinic acids

(+)- and (−)-Methylenolactocins and phaseolinic acids are synthesized in four steps via asymmetric syn- and anti-aldol reactions of chiral N-succinyl-2-oxazolidinones using the same set of reagents.     

Radiative lifetimes of some excited states of neutral xenon

The radiative lifetimes of ten levels belonging to the nf (n=4-7) and three levels belonging to the ns (n=8,9) configuration of XeI have been measured using the high frequency deflection technique together with a delayed coincidence single-photon counting arrangement. Lifetimes of some of the levels have been measured for the first time. The results have been compared with other experimental and theoretical values.     

Experimental lifetimes of some levels of KrI

Lifetime of nine levels belonging to the and configuration of neutral krypton have been measured by high-frequency deflection technique with a delayed coincidence single photon counting arrangement. The results have been compared with other experimental and theoretical values. The lifetimes of the 9s[3/2]₁ and 7p[1/2]₀ levels have been measured for the first time.     

Precise toppling balance, quenched disorder, and universality for sandpiles

A single sandpile model with quenched random toppling matrices captures the crucial features of different models of self-organized criticality. With symmetric matrices avalanche statistics falls in the multiscaling Bak-Tang-Wiesenfeld universality class. In the asymmetric case the simple scaling of the Manna model is observed. The presence or absence of a precise toppling balance between the amount of sand released by a toppling site and the total quantity the same site receives when all its neighbors topple once determines the appropriate universality class.     

Solitons in a relativistic plasma with negative ions

The interaction of the nonlinearity and the dispersiveness causing the solitary waves is studied in a relativistic plasma with negative ions through the derivation of a nonlinear partial-differential equation known as the Korteweg-de Vries equation. The negative ions play a salient part in the existence and behavior of the solitons and could be of interest in laboratory plasmas. First, the observations are made in a nonisothermal plasma, and later the reduction to the nonisothermality of the plasma shows entirely different characteristics as compared to the solitons in the isothermal plasmas. Comparison with the various solitons is emphasized