Nonlinear d10-ML2 Transition-Metal Complexes

Invited for this month′s cover is the group of Prof. F. Matthias Bickelhaupt. The cover picture illustrates the authors′ quantum chemical finding that π electrons can significantly bend otherwise linear d¹⁰-ML₂ complexes through backbonding. For more details, see the Full Paper on p. 106 ff.The Group of F. Matthias BickelhauptDepartment of Theoretical Chemistry Amsterdam Center for Multiscale Modeling VU University E-mail: ln.uv@tpuahlekciB.M.FInstitute for Molecules and Materials Radboud University Nijmegen     

Magnetic particle detection by frequency mixing for immunoassay applications

For magnetic immunoassay applications, a novel magnetic reader for quantification of magnetic particle concentrations has been developed. Upon magnetic excitation at two distinct frequencies incident on the sample, the response signal generated at a sum frequency is detected. The low-frequency field component periodically drives the magnetic particles into saturation, which is probed by the high-frequency field. The appearance of frequency mixing lines is highly specific to the nonlinearity of the superparamagnetic particles’ magnetization. The optimization of field coils, differential pickup coil, preamplifier, demodulators and filters are discussed. The output signal is linear for four orders of magnitude in iron concentration.     

Development of a common fully stereocontrolled access to the medicinally important and promising prostacyclin analogues iloprost, 3-oxa-iloprost and cicaprost

We describe new fully stereocontrolled syntheses of the prostacyclin analogues iloprost (2), the most active component of the drugs Ilomedin and Ventavis, and 3-oxa-iloprost (3), a derivative that is expected to have a significantly higher metabolic stability than 2 perhaps allowing an oral application. The syntheses are based on the same strategy and chiral bicyclic building block as used in the synthesis of cicaprost (4), the third most potent analogue that exhibits, besides prostacyclin-like activities, antimetastatic activities. Reaction of the enantiopure C6-C13 bicyclic aldehyde 17 with Cl(3)CCOOH/Cl(3)CCOONa afforded trichlorocarbinol 24 which was converted via mesylate 25 to the C6-C14 bicyclic alkyne 9. The palladium-catalysed hydrostannylation of alkyne 9 gave with high regio- and stereoselectivity the alkenylstannane 26, Sn/Li exchange of which afforded the E-configured alkenyllithium derivative 8. Coupling of the C6-C14 building block 8 with the enantiopure C15-C20 building block, the N-methoxyamide 7, gave the C6-C20 bicyclic ketone 6 in high yield without epimerisation at C16. The configuration at C15 of iloprost (2) and 3-oxa-iloprost (3) was established through a highly diastereoselective reduction of ketone 6 with catecholborane and the chiral oxazaborolidine 28 which furnished alcohol (15S)-29. The highly stereoselective conversions of alcohol (15S)-29 to iloprost (2) and 3-oxa-iloprost (3), which include as key stereoselective steps an olefination with a chiral phosphonoacetate and a copper-mediated allylic alkylation, have already been described.     

Some spectroscopic properties of cyclic organolead compounds I

The nuclear magnetic resonance and infrared properties of two new cyclic organolead compounds are discussed.     

Direct measurement of the spin Hamiltonian and observation of condensation of magnons in the 2D frustrated quantum magnet Cs2CuCl4

We propose a method for measuring spin Hamiltonians and apply it to the spin- 1/2 Heisenberg antiferromagnet Cs2CuCl4, which shows a 2D fractionalized resonating valence bond state at low fields. By applying strong fields we fully align the spin moment of Cs2CuCl4, transforming it into an effective ferromagnet. In this phase the excitations are conventional magnons and their dispersion relation measured using neutron scattering give the exchange couplings directly, which are found to form an anisotropic triangular lattice with small Dzyaloshinskii-Moriya terms. Using the field to control the excitations we observe Bose condensation of magnons into an ordered ground state.