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[Abstract] N,N′-Bis(2-aminobenzyl)-4,13-diaza-18-crown-6 (L) is a versatile receptor able to adapt to the coordinative preferences of different metal cation guests. With first-row transition metal ions, L tends to form binuclear complexes but, depending on the nature of the particular metal ion, the structure of the binuclear complex may be very different. Herein we report a study of the structure and magnetic properties of the corresponding nickel(II) and cobalt(II) complexes. The X-ray crystal structure of the nickel complex (1), with formula [Ni2(L)(CH3CN)4](ClO4)4·CH3CN, shows that this compound presents a symmetric coordination environment with L adopting an anti arrangement. Each Ni(II) ion is six-coordinate in a distorted octahedral environment, and both metal ions are quite far from each other. On the other hand, the X-ray crystal structure of the cobalt complex (2), with formula [Co(L)(μ-OH)Co(CH3CN)](ClO4)3, reveals a rather different structure. Coordination number asymmetry is found: one of the Co(II) is five-coordinate in a distorted trigonal-bipyramidal coordination environment, while the second Co(II) ion is six-coordinate in a distorted octahedral arrangement. Now L adopts a syn arrangement and a hydroxide group acts as a bridge between both cobalt ions. This hydroxo-bridged Co(II) binuclear complex shows structural features that mimic the active site of methionine aminopeptidases. The magnetic properties of 1 and 2 have been investigated in the temperature range 2.0–300 K. Whereas 1 displays a Curie law except for temperatures below 50 K where zero-field splitting of the S = 1 ground state is observed, antiferromagnetic exchange in the singular asymmetric binuclear Co(II) complex 2 has been observed. This magnetic behaviour has been fitted considering first-order spin–orbit coupling in the assumed axially distorted octahedral site and totally quenched orbital contribution in the five-coordinate site in which zero-field splitting of the S = 3/2 ground state is operative. Galicia. Consellería de Innovación, Industria e Comercio; PGIDIT03TAM10301PR Ministerio de Educación y Ciencia; CTQ 2004-03456

In the structure of the title compound, 28,31,36,39-tetraoxa-9,17,42-triaza-1,25-diazoniapentacyclo[23.8.5.1(11,15).0(3,8).0(18,23)]nonatriaconta-3,5,7,9,11,13,15,16,18,20,22-undecene bis(perchlorate), C33H43N5O(4)2+.2ClO4- or (H2L)(ClO4)2, the cation and one of the two independent anions lie on crystallographic twofold axes, while the second perchlorate anion is disordered about a centre of inversion. The conformation of the macrobicycle L is conditioned by two strong intramolecular hydrogen-bonding interactions involving the pivot and imine N atoms, and is quite different from that observed when a metal ion is placed inside its cavity. The two imine groups are not coplanar with the pyridine moiety, and the deviation from planarity is considerably larger than that found in the corresponding Ba complex. Moreover, the fold of the macrobicycle in H2L2+ causes a significant approach of the two pivot N atoms compared with their disposition in the Ba complex. This is the first X-ray crystal structure analysis of an uncoordinated Schiff base lateral macrobicycle.

The Schiff base N,N'-ethylenebis(pyridoxylideneiminato) (H(2)pyr(2)en, 1) was synthesized by reaction of pyridoxal with ethylenediamine; reduction of H(2)pyr(2)en with NaBH(4) yielded the reduced Schiff base N,N'-ethylenebis(pyridoxylaminato) (H(2)Rpyr(2)en, 2); their crystal structures were determined by X-ray diffraction. The totally protonated forms of 1 and 2 correspond to H(6)L(4+), and all protonation constants were determined by pH-potentiometric and (1)H NMR titrations. Several vanadium(IV) and vanadium(V) complexes of these and other related ligands were prepared and characterized in solution and in the solid state. The X-ray crystal structure of [V(V)O(2)(HRpyr(2)en)] shows the metal in a distorted octahedral geometry, with the ligand coordinated through the N-amine and O-phenolato moieties, with one of the pyridine-N atoms protonated. Crystals of [(V(V)O(2))(2)(pyren)(2)].2 H(2)O were obtained from solutions containing H(2)pyr(2)en and oxovanadium(IV), where Hpyren is the "half" Schiff base of pyridoxal and ethylenediamine. The complexation of V(IV)O(2+) and V(V)O(2) (+) with H(2)pyr(2)en, H(2)Rpyr(2)en and pyridoxamine in aqueous solution were studied by pH-potentiometry, UV/Vis absorption spectrophotometry, as well as by EPR spectroscopy for the V(IV)O systems and (1)H and (51)V NMR spectroscopy for the V(V)O(2) systems. Very significant differences in the metal-binding abilities of the ligands were found. Both 1 and 2 act as tetradentate ligands. H(2)Rpyr(2)en is stable to hydrolysis and several isomers form in solution, namely cis-trans type complexes with V(IV)O, and alpha-cis- and beta-cis-type complexes with V(V)O(2). The pyridinium-N atoms of the pyridoxal rings do not take part in the coordination but are involved in acid-base reactions that affect the number, type, and relative amount of the isomers of the V(IV)O-H(2)Rpyr(2)en and V(V)O(2)-H(2)Rpyr(2)en complexes present in solution. DFT calculations were carried out and support the formation and identification of the isomers detected by EPR or NMR spectroscopy, and the strong equatorial and axial binding of the O-phenolato in V(IV)O and V(V)O(2) complexes. Moreover, the DFT calculations done for the [V(IV)O(H(2)Rpyr(2)en)] system indicate that for almost all complexes the presence of a sixth equatorial or axial H(2)O ligand leads to much more stable compounds.

The X-ray structure of the sodium salt of [Gd(DOTP)]5- shows two different chelates, [Gd(1)(DOTP)]5- and [Gd(2)(DOTP)]5-, bound at either surface of a sheet formed by a cluster of hydrated Na+ ions. Each [Gd(1)(DOTP)]5- anion binds directly to four Na+ ions of this cluster through the free oxygen atoms of the phosphonate groups of the adjacent ligand, while each [Gd(2)(DOTP)]5- unit is connected to the cluster via hydrogen bonds only. The Gd3+ ions in the two moieties do not have any inner-sphere water molecules, and are eight-coordinate. Their coordination polyhedra are twisted square antiprisms, with slightly different twist angles. These mprime isomers are found in the crystal structure as racemic mixtures of enantiomers. Only one set of NMR resonances is observed in aqueous solution, corresponding to an averaged mprime isomer. In this crystal structure, the Na+ ions bind the phosphonate oxygen atoms of the [Gd(1)(DOTP)]5- anion at positions far removed from the main symmetry axis. This is significantly different from the binding mode(s) previously proposed to be occurring in solution between Na+ and [Tm(DOTP)]5-, based on the interpretation of solution paramagnetic 23Na NMR shifts. This could arise as a result of the effects of the cluster of hydrated Na+ ions that are present, which may hinder axial binding modes and distort lateral binding modes. Further, in the crystal structure, both types of Gd3+ centers have four second-sphere water molecules that are located at distances (4.2-4.5 Å) significantly longer than those previously proposed from the analysis of the NMRD data of [Gd(1)(DOTP)]5-. This is a result of the coordination of Na+ by these water molecules, thus preventing their direct interaction with the phosphonate oxygen atoms. However, in solution such second-sphere water molecules can interact strongly with the phosphonate ligand oxygen atoms, resulting in efficient relaxation if their binding has relatively long lifetimes (> 50 ps). Rotational immobilization will amplify this contribution, thus making it similar to outer-sphere relaxation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

The Schiff bases H3dfmp(L)2 obtained by the condensation of 2,6-diformyl-4-methylphenol and hydrazones [L = isonicotinoylhydrazide (inh), nicotinoylhydrazide (nah) and benzoylhydrazide (bhz)] are prepared and characterized. By reaction of [V(IV)O(acac)2] and the H3dfmp(L)2 in methanol the V(IV)O-complexes [V(IV)O{Hdfmp(inh)2}(H2O)] (1), [V(IV)O{Hdfmp(nah)2}(H2O)] (2) and [V(IV)O{Hdfmp(bhz)2}(H2O)] (3) were obtained. Upon their aerial oxidation in methanol [V(V)O(OMe)(MeOH){Hdfmp(inh)2}] (4), [V(V)O(OMe)(MeOH){Hdfmp(nah)2}] (5) and [V(V)O(OMe)(MeOH){Hdfmp(bhz)2}] (6) were isolated. In the presence of KOH, oxidation of 1-3 results in the formation of [V(V)O2{H2dfmp(inh)2}]n·5H2O (7), K[V(V)O2{Hdfmp(nah)2}] (8) and K[V(V)O2{Hdfmp(bhz)2}] (9). All compounds are characterized in the solid state and in solution, namely by spectroscopic techniques (IR, UV-Vis, EPR, (1)H, (13)C and (51)V NMR), and DFT is also used to calculate the V(IV) hyperfine coupling constants of V(IV)-compounds and (51)V NMR chemical shifts of several V(V)-species and assign them to those formed in solution. Single crystal X-ray analysis of [V(V)O(OMe)(MeOH){Hdfmp(bhz)2}] (6) and [V(V)O2{H2dfmp(inh)2}]n·5H2O (7) confirm the coordination of the ligand in the dianionic (ONO(2-)) enolate tautomeric form, one of the hydrazide moieties remaining non-coordinated. In the case of 7 the free N(pyridine) atom of the inh moiety coordinates to the other vanadium center yielding a polynuclear complex in the solid state. It is also demonstrated that the V(V)O2-complexes are catalyst precursors in the oxidative bromination of styrene by H2O2, therefore acting as functional models of vanadium dependent haloperoxidases. Plausible intermediates involved in the catalytic process are established by UV-Vis, (51)V NMR and DFT studies.

In the crystal structure of (perchlorato-κ2 O,O′))(28,31,36,39tetraoxa-1,9,17,25,42-pentaazapentacyclo[23.8.5.111,15.03,8.018,23]nonatriaconta-3,5,7,9,11,13,15,16,18,20,22-undecaene-κ8 N 1,N 9, N 17,N 42,O 28,O 31,O 36,O 39)barium(II) perchlorate, [Ba(ClO4)(C33H41N5O4)](ClO4), the BaII cation is situated in the macrobicyclic cavity, bound to only eight of the nine available donor atoms of the Schiff base macrobicyclic receptor. The pivotal N5 atom does not belong to the coordination sphere of the BaII ion, in spite of its endo conformation with the lone pair directed towards the inside of the cavity. The BaII ion completes its coordination core with two O atoms of one bidentate perchlorate group.

In the crystal structure of (acetonitrile-kappaN)[13-methyl-39-oxido-1,17,25-triaza-9-azonia-28,31,36-trioxapentacyclo[23.8.5.1(11,15).0(3,8).0(18,23)]nonatriaconta-3,5,7,9,11,13,15(39),16,18,20,22-undecaene-kappa(7)N(1),N(17),N(25),O(28),O(31),O(36),O(39)](perchlorato-kappa(2)O,O')barium(II) perchlorate acetonitrile hemisolvate, [Ba(ClO(4))(C(2)H(3)N)(C(33)H(40)N(4)O(4))]ClO(4) x 0.5CH(3)CN, the barium(II) cation is asymmetrically situated in the macrobicyclic cavity and is bound to seven of the eight heteroatoms of the macrobicyclic ligand, to the N atom of an acetonitrile molecule and to two O atoms of one perchlorate group. The azonia N atom is not coordinated to the barium(II) cation and is involved in an intramolecular hydrogen-bonding interaction with the oxido O atom.

The X-ray crystal structure of the title complex, [Ba(NCS) 2 -(C 24 H 36 N 4 O 3 )], indicates that the Ba II cation is nine-coordinate in the solid state, being fully encapsulated by the organic receptor ligand. The receptor adopts a syn arrangement, with both pendant arms oriented on the same side of the crown moiety. The distance between the two amine N atoms is 3.911 (12) A, while the pivotal N atoms are 5.322 (10) A apart.

The Schiff base (Hfsal-aepy) derived from 3-formylsalicylic acid and 2-(2-aminoethyl)pyridine has been covalently bonded to chloromethylated polystyrene cross-linked with 5% divinylbenzene (PS-Hfsal-aepy). Treatment of [V(IV)O(acac)(2)] with PS-Hfsal-aepy in dimethylformamide (DMF) gave the oxidovanadium(IV) complex PS-[V(IV)O(fsal-aepy)(acac)] 1, which on oxidation yielded the dioxidovanadium(V) PS-[V(V)O(2)(fsal-aepy)] 2 complex. The corresponding neat complexes, [V(IV)O(sal-aepy)(acac)] 3 and [V(V)O(2)(sal-aepy)] 4 have also been prepared. The compounds are characterized in solid state and in solution, namely by spectroscopic techniques (IR, UV-Vis, EPR, (1)H, (13)C and (51)V NMR), thermal as well as field-emission scanning electron micrograph (FE-SEM) studies. The crystal and molecular structure of [V(IV)O(sal-aepy)(acac)] was solved by single-crystal X-ray diffraction. It is a monomeric complex with the tridentate sal-aepy ligand bound equatorially and the two O-atoms of acac(-) bound at equatorial and axial positions. These complexes catalyze the hydroamination of styrene and vinyl pyridine with amines (aniline and diethylamine) yielding a mixture of two hydroaminated products in good yield. Amongst the two hydroaminated products, the anti-Markovnikov product is favored over the Markovnikov one. Plausible intermediates involved in these catalytic processes are established by UV-Vis, EPR and (51)V NMR studies, and an outline of the mechanism is proposed. The EPR spectrum of the polymer supported V(IV)O-complex 1 is characteristic of a magnetically diluted V(IV)O-complex, the resolved EPR pattern indicating that the oxidovanadium(IV) centers are well dispersed in the polymer matrix. Neat complexes exhibit lower conversion along with lower turnover frequency as compared to their polymer-anchored analogues. The polymer-anchored heterogeneous catalysts are free from leaching during catalytic action and are recyclable.

molecular Arrangement of Na3V10O28(C4N3OH5)3(C4N3OH6)3 10H2O in the Solid State. N. Bosnjakovic-Pavlovic , N. Bouhmaida, A. Spasojevic-de Bire, I. Correia, I. Tomaz, F. Avecilla, J. Pessoa, U.B. Mioc, and N.E. Ghermani, Ecole Centrale Paris, SPMS UMR CNRS 8580 1 Grande Voie des Vignes 92295 Châtenay-Malabry, France; Faculty of Physical Chemistry P.O. Box 137, 11001 Belgrade, Serbia-Montenegro; LSM, Faculte des Sciences Semlalia, P.O. Box 2390, 40000 Marrakech, Morocco; Centro de Quimica Estrutural, Instituto Superior Tecnico, Av. Rovisco Pais, P-1049-001 Lisboa, Portugal ; Departamento de Quimica Fundamental, Facultad de Ciencias, Campus da Zapateira s/n, 15071 A Coruna, Spain; PPB UMR CNRS 8612, Faculte de Pharmacie 5 Rue Jean-Baptiste Clement, 92296 Châtenay-Malabry, France. E-mail: nada@spms.ecp.fr, nadab@ffh.bg.ac.yu

The Schiff base axial macrobicyclic ligand L1 forms 4f–4f and 4f–3d cryptates with formula [Gd2(L1 − 3H)(NO3)2](NO3)·1.5H2O (1), [Tb2(L1 − 3H)(NO3)2](NO3)·3EtOH·H2O (2), [GdCu(L1 − 3H)(NO3)](NO3)·H2O (3), [LuCu(L1 − 3H)(NO3)](NO3)·H2O (4) and [GdZn(L1 − 3H)(NO3)](NO3)·H2O (5). The macrobicyclic receptor L1 is an azacryptand N[(CH2)2NCH–R–CHN–(CH2)2]3N (R =1,3-(2-OH-5-Me–C6H2)). The crystal structures of the five compounds have been determined by X-ray crystallography. The ligand is helically wrapped around the two metal ions, leading to pseudo-C3 symmetries around the metals. In the solid state, the conformation of the cation in 1 and 2 is Λ(δδλ)5(δδλ)5 or its enantiomeric form Δ(λλδ)5(λλδ)5, while in 3, 4 and 5 it can be described as Λ(δδλ)5(δ′δ′δ′)5 (or Δ(λλδ)5(λ′λ′λ′)5). In 1, only one enantiomer is found in the crystal lattice, whereas in the other four compounds, both enantiomers are co-crystallised. The magnetic behaviour of the homodinuclear (Gd, Gd) and the heterodinuclear (Gd, Cu) cryptates points to a significant magnetic interaction between the two metal ions. This magnetic interaction is antiferromagnetic in the case of the Gd–Gd cryptate 1 (J = −0.194(6) cm−1), but ferromagnetic for the Gd–Cu one (J = 2.2(1) cm−1). The antiferromagnetic coupling observed for 1 is one of the largest ever reported. Although the ferromagnetic coupling observed for 3 is relatively weak, which is attributed to the strong bending of the bridging network, it is considerably stronger than the one reported for [GdCu(L2 − 3H)(DMF)](ClO4)2·MeCN. In spite of the similar coordination environment of the Gd(III) ion in compounds 1, 3 and 5 their EPR spectra are different, thereby confirming the magnetic interactions between the Gd(III) ion and the Cu(II) ion in 3 and the other Gd(III) ion in 1.

The bibracchial lariat ether N,N′-bis(2-salicylaldiminobenzyl)-4,13-diaza-18-crown-6 (L), in its di-deprotonated form, behaves as a selective receptor for lanthanide(III) ions . It only forms stable complexes with the three lightest members of the lanthanide series, lanthanum(III), cerium(III) and praseodymium(III). The X-ray crystal structures of these three complexes show the metal ion ten-coordinated and deeply buried in the cavity of the dianionic receptor. In all three structures the lariat ether presents a syn arrangement. However, the different size of the encapsulated metal ion modifies the conformation of the receptor, particularly in the fold of the crown, resulting in a very different coordination polyhedron for La(III) (distorted tetracapped trigonal prism) with respect to that of Ce(III) and Pr(III) (bicapped square antiprism). Spectrophotometric titration of the dianionic lariat ether with anhydrous La(ClO4)3 in acetonitrile allowed us to calculate log K[La(L − 2H)] = 4.65(4).

We report here a structural and photophysical study of lanthanide monometallic complexes with the macrobicyclic axial phenolic cryptand N[(CH2)2NCH–R–CHN(CH2)2]3N (R = m-C6H2OH-2-Me-5) L as well as of bimetallic complexes with its de-protonated form (L − 3H)3−. The X-ray crystal structure of [DyL(NO3)](NO3)2·2CH3CN· 0.5H2O shows the metal ion being asymmetrically positioned into the macrobicyclic cavity and bonded to seven donor atoms of L and two oxygen atoms of a bidentate nitrate ion. The X-ray crystal structure of the bimetallic cryptate, [Dy2(L − 3H)(NO3)2](NO3)·3H2O·MeOH, confirms that both Dy(III) ions are held into the cavity of the cryptand at a very short distance from each other, 3.4840(4) A. High resolution laser-excited emission spectra of the crystalline monometallic Eu(III) cryptate point to the presence of a single site with low symmetry for the metal, while lifetime measurements in H2O and D2O solutions allowed us to estimate the number of bound water molecules, q = 1. Both mono- and binuclear Yb(III) cryptates display strong emission upon excitation through the ligand electronic levels, the spectrum of the binuclear complex being consistent with the presence of two Yb(III) ions in different co-ordination environments. Proton NMRD profiles for the mononuclear Gd(III) complex have been measured in the temperature range 5–37 °C and show that the relaxivity is mainly limited by fast rotation; this compound is stable towards acid-catalysed decomposition in aqueous solution only at pH > 5.5.

An NMR, electrochemical and photophysical study has been made of lanthanide(III) complexes with a 18-membered hexadentate Schiff-base N4O2 polyoxaazamacrocycle L1 derived from the condensation of 2,6-bis(2-aminophenoxymethyl)pyridine and 2,6-diformylpyridine, as well as their interaction with the chelating agents 1,10-phenanthroline and 2,2′-bipyridine. Separation of the contact and pseudocontact contributions to the observed 1H NMR lanthanide-induced shift values point to an isostructural series of [Ln(L1)][ClO4]3 (Ln = La–Eu, except Pm) in acetonitrile. The interaction of the lanthanum(III) complex with 1,10-phenanthroline and 2,2′-bipyridine was demonstrated by the use of different spectroscopic techniques and the stability constant for the 1,10-phenanthroline adduct was calculated from 1H NMR data. Upon excitation through the metal excited levels, the terbium(III) complex displays the typical luminescence originating from the excited 5D4 level, while the adduct with 1,10-phenanthroline presents emission upon excitation through the ligand bands. The reaction of 2,6-bis(2-aminophenoxymethyl)pyridine and 2,6-diformylpyridine and the perchlorate of GdIII or TbIII in ethanol solution yielded a reduced macrocycle L2 instead of the expected complexes of L1. Electrochemical studies in acetonitrile solution showed that the reduction of the imine groups is favoured when the ionic radius of the lanthanide(III) ion decreases.

We report here a structural and photophysical study of lanthanide(III) complexes with the di-deprotonated form of the bibracchial lariat ether N,N‘-bis(2-salicylaldiminobenzyl)-1,10-diaza-15-crown-5. The X-ray crystal structures of [Ce(L2-2H)](ClO4)·0.5H2O (2) and [Sm(L2-2H)](ClO4)·C3H8O (5b) show the metal ion being nine-coordinated and deeply buried in the cavity of the dianionic receptor. Thanks to the formation of a pseudomacrocycle through π−π interaction between one of the phenol rings and one of the benzyl rings, the complexes present a cryptand-like structure in the solid state. 1H and 13C NMR studies on the La(III) complex point that the solid state structure is essentially maintained in acetonitrile solution. High-resolution laser-excited emission spectra of the crystalline Eu(III) complex demonstrate the presence of several coordination sites arising from different conformations of the crown moiety. The ligand-to-Eu(III) energy transfer is relatively efficient at low temperature, but back transfer is implied in the deactivation process, especially at room temperature, because the ligand triplet state lies at very low energy. However, the low energy of the 3ππ* state provides an efficient conversion of the visible light absorbed into near-infrared light emitted by the Nd(III) ion. http://dx.doi.org/10.1021/ic034024t

Lanthanide ions act as templates in the formation of dinuclear Ln(III) complexes with a cryptand ligand bearing three phenolate groups; the presence of both lanthanide ions into the cavity of the cryptand was confirmed by X-ray structure analysis and spectroscopic data.

Complexes of yttrium (III) and lanthanide(III) ions with an axial macrobicycle derived from the 2+3 Schiff-base condensation of tris(2-aminoethyl)amine with 2,6-diformylpyridine have been prepared in high yields using a one-step procedure. The complexes, with formula [M2L](NO3)6 · xH2O · ySolv, (M = Y, La - Lu, except Pm) and [M 2L](ClO4)6 · xH2O · ySolv, (M = La - Er, except Pm ), have been characterised by elemental analysis, molar conductivity, mass, IR and 1H NMR spectroscopy.