Rare-earth ions in porous matrices

Initially motivated by the commercial need for cheaper and environmentally friendly luminescent materials for application in fluorescent lamps and cathode ray tubes, the search for new matrices for optically active species has penetrated a scope far beyond “classical” solid-state materials. Porous matrices with voids ranging from the nano-to the microscale have become the subject of recent investigations. Crystalline, amorphous, organomorphous, nanosized matrices and matrices, which are amorphous on the atomic level but have a translational superstructure on the microscale (zeolites, sol-gel materials, polymers, nanoparticles and photonic crystals), are addressed. The optical technologies covered in this research range from mercury free discharge lamps, plasma displays, organic and polymeric light emitting diodes, and novel laser materials to biophotonics and the new generation of white emitting AlGaN solid-state light emitting diodes (LEDs). Due to their specific properties (e.g., high quantum yields, narrow line emission), rare-earth ions are indispensable components of these approaches, be it in the nanoscaling zeolites, sol-gel matrices, or as the active component in optically functional polymers. Optical properties of hybrid materials composed of either rare-earth ions as such, their complexes, or nanoparticles in these matrices, with potential application in the fields mentioned, will form the scope of the present report.     

Supraconductivity of LaPtSi and LaPtGe

In the ternary compounds LaPtSi and LaPtGe with the LaPtSi-type structure we have observed supraconductivity with a sharp transition temperature of T_c=3.3 K and T_c=3.4 K, respectively. The superconducting properties of these ternary compounds are compared with binary ones which crystallize in the α-ThSi₂-type structure, since the LaPtSi-type structure is a derivative structure of this.     

Experimental study of high spin states in the ground state bands of158,160Er,164,166Yb,and168Hf

Ground state rotational bands in the deformed doubly-even rare earth nuclei^158,160Er,^164,166Yb, and¹⁶⁸Hf have been observed in (α, 8n γ) reactions. The γ-spectra associated with these reactions were studied in-beam using conventional spectroscopic methods. In all five nuclei the nuclear moment of inertia of the ground state rotational states was found to increase abruptly as higher spin states were attained. In a plot of the moment of inertia as a function of the angular velocity all these five nuclei display “backbending” curves. Moreover, in¹⁵⁸Er and¹⁶⁶Yb, the curves after passing through a maximum bend subsequently downwards.     

Regioselectivity of metalation of alkylmercaptoolefins

The monosulfoxide of cis-dialkylmercaptoethylene $\text{6}$ and the β-alkylmercapto acrylnitrile $\text{15}$ deliver on deprotonation with tert.-butyllithium almost exclusively α-deprotonated species. According to reactions with electrophiles these functionally substituted vinyllithium derivatives are configurationally labile.     

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Synthesis and structure of K+ [iPrN=C=P]-, a 1-aza-3lambda3-phospha-3-allenide

2-Isopropyl(trimethylsilyl)amino-1lambda3-phosphaalkyne 1 reacts with potassium tert-butoxide to form potassium 1-isopropyl-1-aza-3lambda3-phospha-3-allenide (2). This compound was structurally characterized as the corresponding 18-crown-6 ether complex 3. The molecular structure of 1 was also determined in order to compare the bonding situation in the anion and the neutral lambda3-phosphaalkyne. Compound 3 contains a nitrogen-carbon-phosphorus group for which the parameters were shown by X-ray structural analysis and quantum chemical calculations to lie between the extrema N-C[triple bond]P and N=C=P, suggesting reactivity typical of an ambident anion. This is indeed the case, as subsequent reaction of 2 with chlorotrimethylsilane at nitrogen regenerates the lambda3-phosphaalkyne 1; with chlorotriphenylsilane the new derivative 4 is formed. In contrast, chlorotrimethylstannane reacts at phosphorus, giving the 1-aza-3lambda3-phosphaallene isopropyliminomethylidene(trimethylstannyl)phosphane 5.     

Conformation of solvent N,N-dimethylpropionamide in the coordination sphere of the zinc(II) ion studied by Raman spectroscopy and DFT calculations

Solvation structure of the zinc(II) ion in N,N-dimethylpropionamide (DMPA) was studied by Raman spectroscopy at varying temperature and by quantum mechanical calculations. No significant ion-pair formation was found for the Zn(ClO4)2 solution in the molality range m(Zn) < 1.5 mol kg(-1), and the solvation number of the zinc(II) ion was determined to be 4, indicating that 6-coordination of DMPA is sterically hindered. Interestingly, DMPA molecules are under equilibrium between planar cis and nonplanar staggered conformers, and the latter is more preferred in the coordination sphere, while the reverse is the case in the bulk. The DeltaG degrees , DeltaH degrees , and TDeltaS degrees values of conformational change from planar cis to nonplanar staggered in the coordination sphere were obtained to be -0.9, -8.5, and -7.5 kJ mol(-1), respectively. Density functional theory (DFT) calculations show that the planar cis conformer is more favorable than the nonplanar staggered one in the 1:2 cluster, as is the case for a single DMPA molecule and H(DMPA)+, indicating that there hardly occurs solvent-solvent interaction through the metal ion in the Zn2+-DMPA 1:2 cluster. On the other hand, the SCF energy of [Zn(planar cis-DMPA)4-n(nonplanar staggered DMPA)n]2+ (n = 0-4) decreases with increasing n, implying that the nonplanar staggered conformer is preferred in the solvate ion. It is thus concluded that solvent-solvent interaction through space, or solvation steric effect, plays a crucial role in the conformational equilibrium in the coordination sphere of the four-solvate metal ion.