ESR of exchange coupled Cr3+ pairs in the dimer Di-μ-Diphenylphosphinatoacetyl-Acetonatochromium(III) (DPACr)

DPACr is a dimeric phosphinate in which the pairs of Cr³⁺ ions are superexchange coupled via -OPO- bridges. The consequences of site anisotropy and inequivalence are demonstrated in the ESR spectra and can be derived using a perturbation scheme on the appropriate Hamiltonian. First and second order fine structure, multiplet shifts, g-shifts and g-anisotropies are discussed. This dimeric system is the simplest member of a class of poly(chromium phosphinates).     

Quantum effects in the low temperature reorientation of N2− in KCl and KI

The electron paramagnetic resonance (EPR) spectra of KCl:N₂^? and KI:N₂^? were studied as a function of temperature and applied uniaxial stress in the temperature range 2–35°K. The molecular reorientation rates were determined for both 60 and 90° reorientations from the motional broadening and narrowing effects in the observed spectra. Although thermally activated in the range 15–35°K for KCl:N₂^?, the parameters deduced from the data are not consistent with a simple classical model of the motion. In both hosts the 90° rotation is markedly faster than the 60° reorientation, in conflict with simple models, but explicable in terms of the suppression of the tunneling matrix elements by polarization of the host crystal. In KI:N₂^?, the 90° reorientation is still apparent at 1·7°K and the spectra clearly show the influence of the symmetry of the nuclear spin states upon the reorientation kinetics, an effect predicted by Sussman.     

Synthetic magnetic opals

We present studies of novel nanocomposites of BiNi impregnated into the structure of opals as well as inverse opals. Atomic force microscopy and high resolution elemental analyses show a highly ordered structure and uniform distribution of the BiNi filler in the matrix. These BiNi-based nanocomposites are found to exhibit distinct ferromagnetic-like ordering with transition temperature of about 675 K. As far as we know there exists no report in literature on any BiNi compound which is magnetic.     

A host-guest optical sensor for aliphatic amines based on lipophilic cyclodextrin

A host-guest optical sensor for the determination of aliphatic amines as exemplified by octylamine is proposed. It is based on the reversible fluorescence enhancement of heptakis(2,6-di-O-isobutyl)-β-cyclodextrin(DOB-β-CD) hosting tetraphenylporphyrin (TPP) immobilized in poly(vinyl chloride) (PVC) membrane by aliphatic amine extracted from aqueous phase into membrane phase. The optimum membrane contained 1.15 wt % TPP, 6.15 wt % DOB-β-CD as sensing reagent and other membrane materials. The fluorescence enhancement of the membrane resulted from the formation of a stable three-component complex among DOB-β-CD, TPP, and aliphatic amines. With the optimum conditions described, the fluorescence response of the sensor to octylamine shows a good correlation with the theoretically derived equation in the range 1.0 × 10^–6 to 8.0 × 10^–4 mol/L. The response characteristics including reversibility, response time, reproducibility and lifetime and selectivity of this optical device are also discussed in detail. This sensor has also been applied for the determination of octylamine in water samples containing interferents with satisfactory recovery.