Au Compound Research Articles

ChemInform Abstract: A Fluxional High‐Nuclearity Gold‐Platinum Cluster: Structure of (Au6Pt(CC‐t‐Bu)(PPh3)7)+(Au(CC‐t‐Bu)2)‐.

AbstractThe air stable title cluster (III) is prepared by 1:1 molar reaction of the Pt(0) complex (I) with the Au(I) compound (II).

High Temperature NMR in the V3 Au Compound

High Temperature NMR in the V₃ Au Compound

Field-dependent specific heat study of the spin-Peierls transition in TTF–AuS4C4(CF3)4

The compound TTF–AuS4C4(CF3)4 is one of the very few existing examples of the spin-Peierls transition, in which a system of 1D antiferromagnetic chains dimerizes spontaneously as a consequence of magnetoelastic coupling with the surrounding lattice. We have studied the spectific heat anomaly accompanying the SP transition for this compound as a function of an applied magnetic field. Our H=0 data differ considerably from those obtained earlier by Wei et al., and in fact remove the discrepancy found by them between their results for TTF-AuS4C4(CF3)4 and the isomorphous TTF–CuS4C4(CF3)4. The differences between the two experiments are probably due to thermal relaxation effects. The combination of the specific heat data now available confirms the conclusion drawn from our previous field-dependent differential susceptibility studies on the Au compound, namely that the SP transition involves a considerable degree of short-range order, starting to develop below T=1.2 Tsp. We have been able to follow the specific heat anomaly for fields up to the multicritical point in the H–T phase diagram.

Thermal and magnetic study of exchange in the quasi-1-D molecular compound, TTF⋅PtS4C4(CF3)4

Single crystal magnetic susceptibility results from 2.5 K to 270 K and specific heat results from 3 K to 16 K are reported for TTF⋅PtS4C4(CF3)4, (TTF=tetrathiafulvalene). The combined results are analyzed using a simple model which ignores differences between the two types of S=1/2 spin carriers and involves a system of ferromagnetic chains treated ’’exactly’’, with interchain antiferromagnetic interaction evaluated in a mean field approximation. Above an apparent ordering transition at 8 K, the susceptibility is well described by the model irrespective of whether the ferromagnetic exchange is Heisenberg, Ising or intermediate to these. The magnetic contribution to the specific heat is obtained using earlier results for the isostructural Au compound. Comparison with specific heat calculations for the Heisenberg, Ising and intermediate cases successfully narrows the ambiguity to an intermediate anisotropic exchange close to the Heisenberg limit.

Excitation functions of191+193Ir,197Au(6Li, xn+yp) compound nuclear reactions at ELi=48?156 MeV

Excitation functions of the compound nuclear reactions191+193Ir,197Au(6Li,xn+yp) forx =3–13 andy=0–2 have been investigated by means of in-beamγ-ray spectroscopy at the 156 MeV6Li beam of the Karlsruhe Isochronous Cyclotron. The beam energy has been varied in the range of 48 to 156 MeV in steps of about 10 MeV by Be-absorber foils in the external beam line. Absolute cross sections have been determined by normalizing the measuredγ-ray intensities to the production cross sections ofK- X-rays in the target. The experimental excitation functions are discussed on the basis of predictions of the preequilibrium (hybrid) model. While in most cases the theoretical calculations fairly well reproduce energy position and shapes of the curves, strong discrepancies in the absolute scale of the cross sections are observed. The theoretical predictions overestimate the (6Li,xn) cross sections by a factor of about 6. Conspicuous anomalies have been detected when comparing the (6Li, xn+1(2)p) reactions with (6Li,xn) reactions. The reactions with emission of one or two protons are considerably enhanced. The discrepancies and anomalies observed are tentatively explained by the influence of direct reaction channels as the6Li break-up, which experimentally proved to be the dominant contribution to the total reaction cross section. The enhancement of the reactions with emission of protons may be a consequence of transfer reactions into highly excited states combined with compound nucleus formation thus implying a cluster effect in preequilibrium emission process.