Effect of the change of the ancillary carboxylate bridging ligand on the SMM and luminescence properties of a series of carboxylate-diphenoxido triply bridged dinuclear ZnLn and tetranuclear Zn2Ln2 complexes (Ln = Dy, Er).

Eleven new dinuclear and tetranuclear compounds of general formulae [Zn(µ-L)(µ-X)Ln(NO3)2]·nS, [Zn2Dy2(µ3-L')2(µ-sal)2(NO3)(CH3OH)](NO3)·5CH3OH and [Zn2Er2(µ3-L')2(µ-sal)2(CH3OH)2](NO3)2·4CH3OH (X = benzoate, anthracenate, diclofenac, salicylate, 2,6-dihydroxybenzoate; Ln = Dy, Er; S = water, acetonitrile, methanol) were prepared from the N,N'-dimethyl-N,N'-bis(2-hydroxy-3-formyl-5-bromobenzyl)ethylenediamine compartmental ligand (H2L). Complexes 1-6 and 9-11 consist of diphenoxido-carboxylate triply bridged compounds, which differ mainly in the carboxylate bridging ligand. It should be noted that the acidic character of the salicylic acid promotes, in the presence of methanol, the methoxylation of the H2L ligand thereby yielding a hemiacetal H3L', which is able to connect the Ln(iii) ions of two ZnLn dinuclear units forming the Zn2Ln2 tetranuclear complexes 7 and 8. All compounds display SMM behaviour in the presence of an external field with effective energy barriers (Ueff) as high as 61 K. Magneto-structural data for these complexes reveal that their SMM behaviour is not only significantly affected by the type of Ln(iii) ion but also by the carboxylate bridging ligand connecting the Zn(ii) and Ln(iii) ions. Photoluminescence properties have also been accomplished, showing that the ligands are able to sensitize lanthanide centred emissions in the visible and near-infrared regions with variable capacity. Moreover, the analysis of the luminescence decay curves reveals emission lifetimes in the range of few microsecond or hundreds of nanoseconds for Dy(iii)-based or Er(iii)-based luminophores, respectively.

A pentacoordinated norbornenyl-acyl-rhodium(iii) complex as a likely intermediate in the catalytic hydroacylation of norbornadiene.

[RhCl(NCO)(nbyl)(PR3)] (nbyl = σ-norbornenyl; NCO = quinoline-8-acyl; R = p-F-C6H4) (1) has been synthesized by the reaction of [Rh(nbd)Cl]2 (nbd = norbornadiene) with 2 equivalents of NCHO (quinoline-8-carbaldehyde) and 2 equivalents of PR3. Compound 1 has been fully characterized in solution and also in the solid state by X-ray diffraction. Compound 1 shows low stability in solution and undergoes slow ring closure isomerization to [RhCl(NCO)(ntyl)(PR3)] (ntyl = σ-nortricyclyl) (2) after 12 hours. Reaction of 1 with an extra equivalent of aldehyde (NCHO) and PR3 led to the formation of [RhCl(H)(NCO)(PR3)2] (3) and an equivalent of ketone, which is a hydroacylation product. The catalytic activity of 3 in the hydroacylation of nbd with NCHO is reported as well as the catalytic activity of compound 1. Compounds 1 and 3 are proposed as intermediate species in the catalytic hydroacylation of norbornadiene with NCHO.

Increasing the effective energy barrier promoted by the change of a counteranion in a Zn-Dy-Zn SMM: slow relaxation via the second excited state.

The trinuclear complex [ZnCl(µ-L)Dy(µ-L)ClZn]PF6 exhibits a single-molecule magnetic behaviour under zero field with a relatively large effective energy barrier of 186 cm(-1). Ab initio calculations reveal that the relaxation of the magnetization is symmetry-driven (the Dy(III) ion possesses a C2 symmetry) and occurs via the second excited state.

Copper(II) succinate complexes with 1,2-di-4-pyridylethane and 1,3-di-4-pyridylpropane.

The compounds poly[di-mu(4)-succinato-mu(2)-1,2-di-4-pyridylethane-dicopper(II)], [Cu(2)(C(4)H(4)O(4))(2)(C(12)H(12)N(2))](n), (I), and poly[di-mu(4)-succinato-mu(2)-1,3-di-4-pyridylpropane-dicopper(II)], [Cu(2)(C(4)H(4)O(4))(2)(C(13)H(14)N(2))](n), (II), exhibit polymeric structures with the dicopper units doubly bridged by bis-bidentate succinate groups and crosslinked by the separator bis(pyridyl) molecules. In (I), the molecule exhibits a centre of inversion located midway between the core Cu-dimer atoms and another that relates half of the bis(pyridyl)ethane ligand to the other half. Compound (II) has a similar molecular packing but with a doubled lattice constant and noncentrosymmetric core units. An antiferromagnetic interaction due to the dinuclear copper units was deduced from magnetic subsceptibility measurements, and spin triplet signals were detected in the electron paramagnetic resonance spectra for both compounds.

Resolution of racemic mixtures of carbocyclic analogues of nucleosides and assignment of their absolute configuration.

Racemic trans-6-chloro-9-[2-(hydroxymethyl)cyclopentyl]purine was resolved using HPLC with a chiral column. The absolute configurations of the enantiomers were determined by NMR studies of their (R)- and (S)-methoxyphenylacetates.