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[EN] Pressure effect investigations on the magnetic behaviour of the 3D SCO polymers {Fe(3CN-py)2[Ag(CN)2]2} · 2/3H2O (1) and {Fe(3CN-py)2[Au(CN)2]2} · 2/3H2O (2) have been carried out in the range of 105 Pa to 0.7 GPa. Despite both compounds are isostructural their magnetic behaviour under applied hydrostatic pressures is very different. Strong nonlinearity in the Tc(P) vs. P plot has been observed for compound 1 a fact which contrasts with the almost linear dependence observed for each spin transition in 2. However, both compounds are extremely sensitive to the application of pressure as well as the Tc(P) vs. P plots denote., Financial support is acknowledged from the Spanish Ministerio de Educación y Ciencia (MEC) (CTQ 2004 03456/BQU) and from the Generalitat Valenciana for the Research Grant ACOMP06/048. A.G. thanks the Universitat Politècnica de València for a predoctoral fellowship. A.B.G. thanks the Spanish MEC for a Research Contract (Programa Ramón y Cajal).

[EN] Two new mononuclear octahedral manganese(III) complexes with the tetradentate equatorial ligand o-phenylenebis(oxamate) (opba) and two aquo (1a) or two pyridine (1b) axial ligands have been synthesized and characterized structurally, magnetically, and electrochemically. The cyclovoltammogram of 1a in acetonitrile (25 degrees C, 0.1 M Bu4NPF6) shows an irreversible one-electron oxidation peak at a high anodic potential (E-ap = 1.03 V versus SCE), while that of 1b shows two well-separated one-electron oxidation peaks at moderate to high anodic potentials (E-ap = 0.92 and 1.27 V versus SCE), the first redox-wave being quasireversible in nature. The access to formally high-valent Mn-IV and Mn-V oxidation states for 1b is attributed to the stabilization effect of axial pyridine ligand coordination. Complex 1b has been used as an efficient catalyst for the aerobic oxidative cleavage of aromatic vic-diols with co-oxidation of pivalaldehyde to pivalic acid. The corresponding aldehydes or ketones are obtained in fair to good yields and moderate selectivities in acetonitrile at 40 degrees C. Under the same experimental conditions, complex la shows lower efficiencies and selectivities than 1b. The modulation of catalytic activity by the axial pyridine ligands highlights the role of oxomanganese(V) species as the putative intermediates in these C-C bond cleavage oxidation reactions., This work was supported by the Ministerio de Ciencia y Tecnología (Spain) (Project BQU2001 3017) and the Ramon¿ y Cajal program. Further support from the Generalitat Valenciana (Spain) (Project CTIDIA2002 131 and AVCYT Grupos 03/168) is also acknowledged. SB and EP thank the Universitat de Valencia and the Ministerio de Educación, Cultura y Deporte (Spain), respectively, for grants. We are specially thankful to S. Currelli for the assistance with the electrochemical measurements.

[EN] A diversity-oriented approach to enantiomerically pure densely substituted pyrazoles, ¿-aryl-¿-pyrazolylatrolactic acid and ¿-aryl-¿-pyrazolylacetophenones has been developed. The approach utilises the conjugated addition of the lithium enolate of the (2S,5S)-cis-1,3-dioxolan-4-one derived from optically active (S)-mandelic acid and pivalaldehyde to several 2-arylidene-1,3-diketones, which proceeds readily to give the corresponding Michael adducts in good yields and diastereoselectivities. The cyclocondensation of the 1,3-diketone moieties present in Michael adducts with several hydrazines leads to enantiomerically pure densely substituted pyrazoles. Subsequent basic hydrolysis of the dioxolanone moiety present in these products leads to enantiomerically pure ¿-aryl-¿-pyrazolylatrolactic acids. Finally, oxidative decarboxylation of these using oxygen, pivalaldehyde and the Co(III)¿Me2opba complex as catalyst gives ¿-aryl-¿-pyrazolylacetophenones. In this approach four points of diversity are introduced, one of them is the configuration of the (S)-mandelic acid, which acts as an umpoled chiral equivalent of the benzoyl anion., Financial supports from the Spanish Government MEC (BQU2001-3017) and from Generalitat Valenciana (Grupos 03/168 and GV05/10) are acknowledged.

[EN] The high-valent bis(oxo)-bridged dimanganese(IV) complexes with the series of binucleating 4.5-X-2-o-phenylenebis(oxamate) ligands (opbaX(2); X = H, Cl, Me) (1a-c) have been synthesized and characterized structurally, spectroscopically and magnetically. Complexes la-c possess unique Mn-2(mu-O)(2) core structures with two o-phenylenediamidate type additional bridges which lead to exceptionally short Mn-Mn distances (2.63-2.65 angstrom) and fairly bent Mn-O-Mn angles (94.1 degrees-94.6 degrees). The cyclovoltammograms of la-c in acetonitrile (25 degrees C, 0.1 M Bu4NPF6) show an irreversible one-electron oxidation peak at moderately high anodic potentials (E-ap = 0.50-0.85 V versus SCE), while no reductions are observed in the potential range studied (down to -2.0 V versus SCE). These dinuclear manganese oxamate complexes are excellent catalysts for the aerobic oxidation of 3,5-di-tert-butylcatechol to the corresponding o-quinone in acetonitrile at 25 degrees C. The order of increasing catecholase activity (k(obs)) with the electron donor character of the ligand substituents as 1b (X = Cl) < 1a (X = H) < 1c (X = Me) correlates with Hammett sigma(+) values (p = -0.95). A mechanism involving initial activation of the catechol substrate by coordination to the dimetal center and subsequent oxidation to quinone by O-2 is proposed, which is consistent with the observed saturation kinetics., This work was supported by the Ministerio de Ciencia y Tecnología (Spain) (Project BQU2001-3017) and the Ramon y Cajal program. Further support from the Generalitat Valenciana (Spain) (Project CTIDIA2002-131 and AVCYT Grupos 03/168) is also acknowledged. E. P. thanks the Ministerio de Educación, Cultura y Deporte (Spain) for a grant.

[FR] Le composé ¿Fe(LI)3¿2¿Fe(H2O)6¿(ClO4)6 (2), LI = 1,10-phénanthroline-5,6-dione, a été synthétisé et caractérisé. La structure cristalline 2 est définie par un assemblage bidimensionnel non covalent, peu commun, constitué par des tectons chiraux ¿Fe(LI)3¿2+, assemblés par des cations ¿Fe(H2O)6¿2+ encapsulés dans des cages. Ces cages sont formées par 12 liaisons hydrogène établies entre les molécules d¿eau coordinées et les groupes dione appartenant à six molecules chirales ¿Fe(LI)3¿2+ ¿, ¿ alternées., [EN] The synthesis and characterisation of [Fe(L-1)(3)](2)[Fe(H2O)(6)](ClO4)(6) (2), L-1 = 1,10-phenanthroline-5,6-dione, is described. The crystal structure 2 is an unprecedented example of two-dimensional non-covalent array made up of [Fe(L-1)(3)](2+) species assembled by [Fe(H2O)(6)](2+) cations encapsulated in pseudo-hexagonal cages. These cages are sustained by 12 hydrogen bonds established between the coordinated water molecules and the dione groups of six alternating Delta, Lambda chiral [Fe(L-1)(3)](2+) moieties. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS., This work was supported by the Spanish Dirección General de Investigación Científica y Técnica (DGICYT) (Project PB97-1397). The authors are thankful to Prof. M. Julve and Dr. R. Ruiz for reviewing this contribution.

[EN] On mixing concentrated aqueous solutions of pdta, Cu(II) and Mn(II) in the ratio 1:1:1 at pH 4.5, single crystals of the complex [Mn(H2O)6][Cu(pdta)]·2H2O (1) (pdta=1,3-propylenediamine-N,N,N'N'-tetraacetate) were obtained. X-ray structural analysis revealed that in the anion [Cu(pdta)]2- the coordination polyhedron around the Cu(II) ion can be described as a tetragonaly distorted CuN2O4 octahedron, whereas the cation [Mn(H2O)6]2+ can be described as a very regular MnO6 octahedron. Thermogravimetric analysis shows that at 110°C compound 1 loses its eight water molecules yielding the anhydrous compound [MnCu(pdta)] (2). Variable-temperature magnetic susceptibility measurements indicate that no magnetic interactions are present in 1 while weak antiferromagnetic interactions occur in 2., This work was partially supported by the CICYT (Spain) through Projects PB97-1397 (Valencia) and APC94-0031 (La Laguna). Instrumental and computing facilities of the Servicio de Espectroscopı́a y Centro de Cálculo de la Universitat de València are gratefully acknowledged.

[EN] Assembly of the tetranuclear oxomanganese(III) acetato cluster [Mn4O2(O2CMe)(7)(phen)(2)](BF4) from the dinuclear oxo-di(acetato)bridged manganese(III) species [Mn2O(O2CMe)(2)(H2O)(2)(phen)(2)](BF4)(2) . 3H(2)O in aqueous/acetic acid MeOH solution occurs via the new 'dimer of dimers' Mn-III complex [Mn2O(O2CMe)(3)(H2O)(phen)(2)](BF4) . MeOH possesing an unprecedent [Mn-4(mu-O)(2)(mu-O2Me)(4) (mu-(OH2O2CMe)-O-...)(2)] core., This work was supported by the DGICYT, Ministerio de Educación y Ciencia (Spain) through project PB97-1397. R. Ruiz thanks the 3MD-EU Network (contract no. ERB 4061, PL97-0197) for a grant.

[EN] Novel two-dimensional polymers, [Fe(L-1)(H2O)(2)(NCX)(2)]. L-1 (L-1 =4.4'-bipyridine (bipy)) (1, 2) and [Fe(L-2)(CH3OH)(2)-(NCX)(2)]. L-2 (L-2 =4,4'-azopyridine (azpy)) (3) and X = S (1, 3), Se (2), have been synthesized and characterized by X-ray crystallography. The structures reveal the formation of tranzs-L-bridged [Fe(NCX)(2)(Y)(2)] where Y=H2O, CH3OH linear chains assembled into two-dimensional networks by hydrogen bonds between the uncoordinated ligand L and the coordinated solvent molecules., We are grateful for financial assistance from the Direction General de Investigation Cientifica y Tecnica (DGICYT) (Spain) through Project PB97-1397. We acknowledge the European Commission for granting the TMR-Network Thermal and Optical Switching of Molecular Spin States (TOSS) , Contract No. ERB-FMRX-CT9&0199EEC/ TMR.

[EN] The compounds [Fe(abpt)(2)(NCS)(2)] (1) and [Fe(abpt)(2)(NCSe)(2)] (2) with abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole have been synthesized. The X-ray structures have been determined at 293 K. 1 and 2 are isostructural and crystallize in the monoclinic space group P2(1)/n with Z = 2, a = 8.538(8), b = 10.246(8), c = 16.45(2) Angstrom, beta = 93.98(9)degrees for 1 and a = 8.623(2), b = 10.243(3), c = 16.585(3) Angstrom, beta = 93.19(2)degrees for 2. In both complexes, the coordination core has a similar pseudo-octahedral geometry with the NCS- (1) and NCSe- (2) groups in the trans-position. Variable-temperature magnetic susceptibility data give evidence for a low-spin (LS)high-spin (HS) conversion centered at T-1/2 around 180 and 224 K for 1 and 2, respectively. The spin conversion takes place gradually, without hysteresis. The enthalpy and entropy changes associated with the spin conversion are evaluated from the DSC measurements: Delta H = 5.8 +/- 0.5 (1) and 8.6 +/- 0.8 kJ mol(-1) (2); BS = 32.5 +/- 3 (1) and 38 +/- 4 J mol(-1) K-1 (2). At 10 K the light-induced excited spin state trapping (LIESST) effect has been observed within the SQUID magnetometer cavity, by irradiating powder samples with a Kr+ laser coupled to an optical fiber. The critical LIESST temperatures T-liesst are around 40 and 32 K for 1 and 2, respectively. The magnetic behavior recorded under light irradiation in the warming and cooling modes has revealed a light-induced thermal hysteresis (LITH) effect. The HS-->LS relaxation kinetics have been investigated in the temperature range 6-40 K. A thermally activated mechanism at elevated temperatures and a nearly temperature independent relaxation behavior at low temperatures can be observed for 1. The very fast relaxation precludes the estimation of the kinetic parameters for 2 at temperatures higher than 10 K. (C) 1999 Elsevier Science S.A. All rights reserved., We thank the financial assistance from the Spanish DGICYT and CICYT through Projects PB97-1397 and MAT97-0987. We acknowledge the European Commission for granting the TMR-Network Thermal and Optical Switching of Molecular Spin States (TOSS) , contract no. ERB-FMRX-CT98-0199EEC/TMR.