The complexes [Cu2(mu-Cl)2(Cl)2(L)2] (L = dialkylpyridine-2,6-dicarboxylate; R = Et, L = depc, 1; R = i-Pr, L = dppc, 2) have been prepared and their magnetic properties studied. The crystal structures of complexes 1 and 2 have been solved. Compound 1 belongs to the P space group with Z = 2, a = 8.3020(10) A, b = 9.2050(10) A, c = 10.065(2) A, alpha = 99.040(10), beta = 100.810(10), and gamma = 106.502(10) whereas 2 belongs to the C2/c space group with Z = 8, a = 11.6360(10) A, b = 25.906(3) A, c = 11.76579(10) A, and beta = 107.900(10). The different alkyl ester substitutes produce substantial structural and electronic differences. The Cu2Cl2 core geometry is planar for 1 whereas it adopts a butterfly shape in the case of 2. Furthermore, in 2 the dppc ligand coordinates only by the carbonyl oxygen atoms whereas in 1 the depc ligand coordinates through carbonyl and alkoxy oxygen atoms. Magnetic susceptibility data show a ferromagnetic coupling between the two Cu(II) centers in both cases (J = 39.9(6) cm(-1) for 1, and J = 51.3(5) cm(-1) for 2) with very weak antiferromagnetic interactions (J ' = -0.59 cm(-1) and -0.57 cm(-1) for 1 and 2, respectively). Theoretical calculations at the extended Hückel level have also been carried out to further understand the electronic nature of complexes 1 and 2.

In this study, a high catalytic activity of palladium nanoparticles immobilized on alumina (Al 2 O 3 ) is reported for the industrially important reduction of aromatic nitro compounds to amino compounds. The palladium nanoparticles were immobilized on alumina by a simple physical precipitation method. The synthesis of palladium nanoparticles was done in ethylene glycol without using any external stabilizing agent. The composite particles exhibited good colloidal stability. The catalytic activity is investigated qualitatively by high performance liquid chromatography (HPLC) and quantitatively by photometrically monitoring the reduction of p-nitrophenol by an excess of sodium borohydride (NaBH 4 ) in the presence of nanocomposites. The kinetic data could be explained by the assumption of pseudo first-order reaction with respect to p-nitrophenol.

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The synthesis, structure, and magnetic properties of two new tetranuclear Cu(II) complexes containing N,N,N',N'-tetraethylpyridine-2,6-dithiocarboxamide (S-dept) of formula [Cu(2)Cl(2)(mu-S-dept)(2)][Cu(2)Cl(4)(mu-Cl)(2)] (1) and [Cu(2)(mu-Cl)(2)(S-dept)(2)][CuCl(3)(EtOH)](2) (2) are reported. Their X-ray crystal structures reveal that the complexes are composed of anionic and cationic dimers, that in both cases contain the metal centers which interact via Coulombic and/or hydrogen bonding interactions. In both cases, the Cu centers in the anionic moieties adopt a slightly distorted tetrahedral geometry whereas for the cationic moieties they adopt a square-pyramidal type of geometry. Magnetic susceptibility data show that compounds 1 and 2 present an overall antiferromagnetic behavior arising from the contribution of both anionic and cationic moieties. For 1, the best fit obtained gave J(1) = -2.62 +/- 0.19 cm(-1), J(2) = -19.54 +/- 0.47 cm(-1), and g(2) = 2.164 +/- 0.004 cm(-1) (R = 8.28 x 10(-5)) whereas for 2 it gave J(1) = 4.48 +/- 2.73 cm(-1), g(1) = 2.20 +/- 0.03, J(2) = -11.26 +/- 2.01 cm(-1), and g(2) = 2.10 +/- 0.03 (R = 1.15 x 10(-4)). The nature of the superexchange pathways in 1 and 2 is discussed on the basis of structural, magnetic, and molecular orbital considerations. Theoretical calculations are performed at the extended Huckel level in order to obtain their molecular orbitals and energies using their crystallographic data.

Reaction of anhydrous CoCl(2) with N,N'-diisopropylisonicotinamide (L) has yielded a coordination polymer containing linear trinuclear [Co(3)L(4)Cl(6)] units with a rare, mixed Co(T(d))-Co(O(h))-Co(T(d)) assembly (compound 1). The central Co(II) ion, of each trinuclear entity, exhibits a distorted octahedral geometry, with two ligand molecules coordinating through their carbonyl oxygen atoms along with two bridging Cl(-) ions and two pyridine N atoms from the neighboring molecules. Also, in each unit, two outer Co(II) ions display distorted tetrahedral geometry, coordinating to one ligand molecule through the pyridine N atom and to three Cl(-) ions (one of them bridged to the central Co(II) and the two acting as a terminal ligands). The magnetic properties of this compound were investigated in the temperature range of 2.0 to 300.0 K. Owing to the complexity of the system and the weak interactions among trinuclear aggregates, the magnetic response has been analyzed using a model which considers these units as isolated systems. In addition, magnetic data has been examined in two separated blocks, above and below 50 K, applying programs VPMAG FORTRAN and MAGPACK-fit, respectively. This way, only the most significant effects at each interval of temperature were considered: spin-orbit coupling of the Co(O(h)), at high temperatures and zero-field splitting parameters of the Co(T(d)) at the low. Spin-spin magnetic interaction has been taken into account for the whole range of temperatures. As a result, the analysis of the magnetic data shows that, within every trinuclear unit, the central position matches well with a high-spin Co(II) (S = 3/2) and also reveals weak ferromagnetic interactions between the Co(O(h)) and the two terminal Co(T(d)) ions (J = +0.34 cm(-1)).