Orbital Configurations and Magnetic Properties of Double-Layered Antiferromagnet Cs3_3Cu2_2Cl4_4Br3_3

We report the single-crystal X-ray analysis and magnetic properties of a new double-layered perovskite antiferromagnet, Cs$_3$Cu$_2$Cl$_4$Br$_3$. This structure is composed of Cu$_2$Cl$_4$Br$_3$ double layers with elongated CuCl$_4$Br$_2$ octahedra and is closely related to the Sr$_3$Ti$_2$O$_7$ structure. An as-grown crystal has a singlet ground state with a large excitation gap of $\Delta/k_{\rm B}\simeq 2000$ K, due to the strong antiferromagnetic interaction between the two layers. Cs$_3$Cu$_2$Cl$_4$Br$_3$ undergoes a structural phase transition at $T_{\rm s}\simeq330$ K accompanied by changes in the orbital configurations of Cu$^{2+}$ ions. Once a Cs$_3$Cu$_2$Cl$_4$Br$_3$ crystal is heated above $T_{\rm s}$, its magnetic susceptibility obeys the Curie-Weiss law with decreasing temperature even below $T_{\rm s}$ and does not exhibit anomalies at $T_{\rm s}$. This implies that in the heated crystal, the orbital state of the high-temperature phase remains unchanged below $T_{\rm s}$, and thus, this orbital state is the metastable state. The structural phase transition at $T_{\rm s}$ is characterized as an order-disorder transition of Cu$^{2+}$ orbitals.Comment: 6pages. 6figures, to appear in J. Phys. Soc. Jpn. Vol.76 No.

Organonitrile ligated silver complexes with perfluorinated weakly coordinating anions and their catalytic application for coupling reactions

Homogeneous catalytic processes mediated by silver(I) complexes are relatively rare. This work describes the synthesis and characterization of acetonitrile ligated silver salts with three weakly coordinating anions [B(C6F5)(4)](-), [B{C6H3(CF3)(2)}(4)](-) and [(C6F5)(3)B-C3H4N2-B(C6F5)(3)](-). The silver cation is coordinated either by four or by two acetonitrile ligands. All examined Ag(I) complexes show catalytic activity in coupling reactions of terminal alkynes with aldehydes and amines

Asymmetric bipyridine-terpyridine-copper(II) complexes: an approach for new supramolecular architectures

On the way towards novel supramol. assemblies and polymers, several copper(II) complexes consisting of one terpyridine as well as one bipyridine ligand were synthesized in a one-step reaction. The compds. were characterized by UV/VIS spectroscopy and MALDI-TOF mass spectrometry. Single crystals were obtained and their structures were detd. by X-ray analyse

Novel Naphthalene– and Cyclohexa-1,3-diene–Silene Cycloadducts

Auner N, Seidenschwarz C, Herdtweck E, Sewald N. Novel Naphthalene– and Cyclohexa-1,3-diene–Silene Cycloadducts. Angewandte Chemie International Edition. 1991;30(4):444-446