Interpretation of Polarized Absorption and Emission Spectra of Molecules Incorporated in Stretched Polymer Films

Different methods for the interpretation of linear dichroic spectra of molecules incorporated in uniaxial matrices are discussed. A method based on the combination of both polarized absorption and emission measurements is described for the resolution of absorption and emission spectra into their different polarized components, and for the investigation of molecular distributions in the oriented matrix. The distributions of some planar molecules of different shapes incorporated in stretched polyethylene films are presented.     

Anomalous Energy Minima Surfaces

Previous publications^2–5 have examined the phenomenon of level crossings as predicted by the semiempirical techniques CNDO/2⁶, IMDO⁷, and MINDO/3⁸ for certain molecules when the total energy is viewed as a function of some conformational property. The purpose of this article is to examine this same phenomenon using the extended Hückel method(EHM)⁹, the iterated extended Hückel method(IEHM), and an ab-initio procedure with a minimal STO-3G basis set. The molecule chosen for this study is CO₂ due to its structural simplicity and since previous calculations^2–5 have demonstrated level crossing with this molecule.     

Labelling of peptides with <Superscript>99m</Superscript>Tc complexes through the modified C-terminal group

Easy and efficient way to modify of the C-terminus of the peptide using amino acid lysine has been proposed and experimentally verified. The synthesis yield was high (≥85%) and it was found that reactions can be carried out even with microgram amounts of the peptide. Using Fmoc-alanine (as the peptide model) with modified C-terminus the procedure of peptide labelling with monovalent and trivalent ^99mTc complexes has been elaborated.     

FTIR analysis of the hydrolysis rate in the sol–gel formation of gadolinia-doped ceria with acetylacetonate precursors

This study reveals that Fourier transform infrared is an effective analytical tool in probing the extent of hydrolysis of cerium and gadolinium acetylacetonates dissolved in methanol. It is found that these acetylacetonates have relatively fast hydrolysis rates at the early stage of hydrolysis (<6 h). However, their hydrolysis rates become very slow beyond 6-h of hydrolysis and decrease to near zero after 55-h of hydrolysis. As a result, hydrolysis cannot be completed even after 170 h at room temperature. These phenomena suggest that the first and second acetylacetone ligands chelated to Ce³⁺ and Gd³⁺ ions can actually be hydrolyzed with relative ease at room temperature, similar to alkoxide ligands. It is the last acetylacetone ligand that is very difficult to be hydrolyzed.     

Synthesis,Complexes and Metal Extraction Ability of R1R2NC(X)NHP(Y)(0Ph)2

Abstract

The new 1,1-disubstituted 3-diphenoxy(thio)phosphoryl-(thio)ureas, R¹R²NC(X)NHP(0Ph)₂, HA, with X,Y = O,S, were synthesized by addition of secondary mines to the corresponding P-iso(thio)cyanates. This reaction is reversible if X,Y = S. (PhO)₂P(Y)Cl reacts with H₂NC(X)NR₂ in the presence of an HCl acceptor only if X,Y a 0. Side reactions are observed. Phosphorylated derivatives of biuret were isolated from such a reaction mixture.     

Synthesis, radiochemistry and stability of the conjugates of technetium-99m complexes with Substance P

Two types of technetium-99m complexes: (i) with the Hynic ligand linked to Substance P(1–11) and (ii) of the type ‘4 + 1’ consisting of tetradentate tripodal chelator tris(2-mercaptoethyl)-amine and monodentate isocyanide ligand previously coupled with Substance P(1–11), have been prepared on the n.c.a. scale. The obtained conjugates exhibit different lipophilicity and high stability in neutral aqueous solutions, even in the presence of excess concentration of histidine/cysteine competitive standard ligands. The conjugate (^99mTc(NS₃)(CN))₂–SP containing two technetium-99m species in the molecule may be expected to be an extremely good diagnostic radiopharmaceutical.     

Ordering in spatially anisotropic triangular antiferromagnets

We investigate the phase diagram of the anisotropic spin-1/2 triangular lattice antiferromagnet, with interchain diagonal exchange J' much weaker than the intrachain exchange J. We find that fluctuations lead to a competition between (commensurate) collinear antiferromagnetic and (zigzag) dimer orders. Both states differ in symmetry from the spiral order known to occur for larger J', and are therefore separated by quantum phase transitions from it. The zero-field collinear antiferromagnet is succeeded in a magnetic field by magnetically ordered spin-density-wave and cone phases, before reaching the fully polarized state. Implications for the anisotropic triangular magnet Cs2CuCl4 are discussed.