Modulating magnetic dynamics of three Dy2 complexes through keto-enol tautomerism of the o-vanillin picolinoylhydrazone ligand

Complexation of dysprosium(III) with the heterodonor chelating ligand o-vanillin picolinoylhydrazone (H(2)ovph) in the presence of different bases affords three new dinuclear dysprosium(III) coordination compounds, namely, [Dy(2)(ovph)(2)(NO(3))(2)(H(2)O)(2)]·2H(2)O (1), [Dy(2)(Hovph)(ovph)(NO(3))(2)(H(2)O)(4)]·NO(3)·2CH(3)OH·3H(2)O (2), and Na[Dy(2)(Hovph)(2)(μ(2)-OH)(OH)(H(2)O)(5)]·3Cl·3H(2)O (3), where the aroylhydrazone ligand adopts different coordination modes in respective structures depending on the reaction conditions, as revealed by single-crystal X-ray analyses to be due to their tautomeric maneuver. The magnetic properties of 1-3 are drastically distinct. Compounds 1 and 2 show single-molecule-magnet behavior, while no out-of-phase alternating-current signal is noticed for 3. The structural differences induced by the different coordinate fashions of the ligand may influence the strength of the local crystal field, the magnetic interactions between metal centers, and the local tensor of anisotropy on each Dy site and their relative orientations, therefore generating dissimilar dynamic magnetic behavior.     

2-Aminoisobutyric acid in Co(II) and Co(II)/Ln(III) chemistry: homometallic and heterometallic clusters

The synthesis and magnetic properties of 13 new homo- and heterometallic Co(II) complexes containing the artificial amino acid 2-amino-isobutyric acid, aibH, are reported: [Co(II)(4)(aib)(3)(aibH)(3)(NO(3))](NO(3))(4)·2.8CH(3)OH·0.2H(2)O (1·2.8CH(3)OH·0.2H(2)O), {Na(2)[Co(II)(2)(aib)(2)(N(3))(4)(CH(3)OH)(4)]}(n) (2), [Co(II)(6)La(III)(aib)(6)(OH)(3)(NO(3))(2)(H(2)O)(4)(CH(3)CN)(2)]·0.5[La(NO(3))(6)]·0.75(ClO(4))·1.75(NO(3))·3.2CH(3)CN·5.9H(2)O (3·3.2CH(3)CN·5.9H(2)O), [Co(II)(6)Pr(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Pr(NO(3))(5)]·0.41[Pr(NO(3))(3)(ClO(4))(0.5)(H(2)O)(1.5)]·0.59[Co(NO(3))(3)(H(2)O)]·0.2(ClO(4))·0.25H(2)O (4·0.25H(2)O), [Co(II)(6)Nd(III)(aib)(6)(OH)(3)(NO(3))(2.8)(CH(3)OH)(4.7)(H(2)O)(1.5)]·2.7(ClO(4))·0.5(NO(3))·2.26CH(3)OH·0.24H(2)O (5·2.26CH(3)OH·0.24H(2)O), [Co(II)(6)Sm(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Sm(NO(3))(5)]·0.44[Sm(NO(3))(3)(ClO(4))(0.5)(H(2)O)(1.5)]·0.56[Co(NO(3))(3)(H(2)O)]·0.22(ClO(4))·0.3H(2)O (6·0.3H(2)O), [Co(II)(6)Eu(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)OH)(4.87)(H(2)O)(1.13)](ClO(4))(2.5)(NO(3))(0.5)·2.43CH(3)OH·0.92H(2)O (7·2.43CH(3)OH·0.92H(2)O), [Co(II)(6)Gd(III)(aib)(6)(OH)(3)(NO(3))(2.9)(CH(3)OH)(4.9)(H(2)O)(1.2)]·2.6(ClO(4))·0.5(NO(3))·2.58CH(3)OH·0.47H(2)O (8·2.58CH(3)OH·0.47H(2)O), [Co(II)(6)Tb(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Tb(NO(3))(5)]·0.034[Tb(NO(3))(3)(ClO(4))(0.5)(H(2)O)(0.5)]·0.656[Co(NO(3))(3)(H(2)O)]·0.343(ClO(4))·0.3H(2)O (9·0.3H(2)O), [Co(II)(6)Dy(III)(aib)(6)(OH)(3)(NO(3))(2.9)(CH(3)OH)(4.92)(H(2)O)(1.18)](ClO(4))(2.6)(NO(3))(0.5)·2.5CH(3)OH·0.5H(2)O (10·2.5CH(3)OH·0.5H(2)O), [Co(II)(6)Ho(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·0.27[Ho(NO(3))(3)(ClO(4))(0.35)(H(2)O)(0.15)]·0.656[Co(NO(3))(3)(H(2)O)]·0.171(ClO(4)) (11), [Co(II)(6)Er(III)(aib)(6)(OH)(4)(NO(3))(2)(CH(3)CN)(2.5)(H(2)O)(3.5)](ClO(4))(3)·CH(3)CN·0.75H(2)O (12·CH(3)CN·0.75H(2)O), and [Co(II)(6)Tm(III)(aib)(6)(OH)(3)(NO(3))(3)(H(2)O)(6)]·1.48(ClO(4))·1.52(NO(3))·3H(2)O (13·3H(2)O). Complex 1 describes a distorted tetrahedral metallic cluster, while complex 2 can be considered to be a 2-D coordination polymer. Complexes 3-13 can all be regarded as metallo-cryptand encapsulated lanthanides in which the central lanthanide ion is captivated within a [Co(II)(6)] trigonal prism. dc and ac magnetic susceptibility studies have been carried out in the 2-300 K range for complexes 1, 3, 5, 7, 8, 10, 12, and 13, revealing the possibility of single molecule magnetism behavior for complex 10.     

Metal ion-controlled self-assembly using pyrimidine hydrazone molecular strands with terminal hydroxymethyl groups: a comparison of Pb(II) and Zn(II) complexes

Metal complexation studies were performed with the ditopic pyrimidine-hydrazone (pym-hyz) strand 6-hydroxymethylpyridine-2-carboxaldehyde (2-methyl-pyrimidine-4,6-diyl)bis(1-methylhydrazone) (1) and Pb(ClO(4))(2)·3H(2)O, Pb(SO(3)CF(3))(2)·H(2)O, Zn(SO(3)CF(3))(2), and Zn(BF(4))(2) to examine the ability of 1 to form various supramolecular architectures. X-ray crystallographic and NMR studies showed that coordination of the Pb(II) salts with 1 on a 2:1 metal/ligand ratio in CH(3)CN and CH(3)NO(2) resulted in the linear complexes [Pb(2)1(ClO(4))(4)] (2), [Pb(2)1(ClO(4))(3)(H(2)O)]ClO(4) (3), and [Pb(2)1(SO(3)CF(3))(3)(H(2)O)]SO(3)CF(3) (4). Two unusually distorted [2 × 2] grid complexes, [Pb1(ClO(4))](4)(ClO(4))(4) (5) and [Pb1(ClO(4))](4)(ClO(4))(4)·4CH(3)NO(2) (6), were formed by reacting Pb(ClO(4))(2)·6H(2)O and 1 on a 1:1 metal/ligand ratio in CH(3)CN and CH(3)NO(2). These grids formed despite coordination of the hydroxymethyl arms due to the large, flexible coordination sphere of the Pb(II) ions. A [2 × 2] grid complex was formed in solution by reacting Pb(SO(3)CF(3))(2)·H(2)O and 1 on a 1:1 metal/ligand ratio in CH(3)CN as shown by (1)H NMR, microanalysis, and ESMS. Reacting the Zn(II) salts with 1 on a 2:1 metal/ligand ratio gave the linear complexes [Zn(2)1(H(2)O)(4)](SO(3)CF(3))(4)·C(2)H(5)O (7) and [Zn(2)1(BF(4))(H(2)O)(2)(CH(3)CN)](BF(4))(3)·H(2)O (8). (1)H NMR studies showed the Zn(II) and Pb(II) ions in these linear complexes were labile undergoing metal ion exchange. All of the complexes exhibited pym-hyz linkages in their cisoid conformation and binding between the hydroxymethyl arms and the metal ions. No complexes were isolated from reacting either of the Zn(II) salts with 1 on a 1:1 metal/ligand ratio, due to the smaller size of the Zn(II) coordination sphere as compared to the much larger Pb(II) ions.     

A diabolo-shaped Dy9 cluster: synthesis, crystal structure and magnetic properties

The reaction of Dy(NO(3))(3)·6H(2)O with the ligand 2-((1-hydroxybutan-2-ylimino)methyl)phenol (H(2)L, ) generates the nonanuclear compound [Dy(9)L(8)(μ(3)-OH)(8)(μ(4)-OH)(2)(CH(3)OH)(8)](OH)(CH(3)OH)(3) (Dy(9)), whose single-crystal X-ray structure reveals the presence of two square pyramidal pentanuclear units assembled via the apical metal center. The square pyramidal core of a previously reported [Dy(5)(μ(4)-OH)(μ(3)-OH)(4)(μ-η(2)-Ph(2)acac)(4)(η(2)-Ph(2)acac)(6)] (Dy(5); Ph(2)acac = dibenzoylmethanide), is structurally related to those herein described; however, the magnetic properties of Dy(9) and Dy(5) are drastically different. Indeed, Dy(5) shows slow relaxation of magnetization while no out-of-phase ac signal is noticed for Dy(9). The underlying mechanism is not clear due to the complexity of such systems; however, the different anisotropy of the respective structures, which is dictated by the combination of the metal topology, the ligands involved and the structural parameters of the molecule, is mostly responsible for the distinctive relaxation dynamics observed.     

New diamondoid-like [Cu3B(μ-O)6] core self-assembled from Bis-Tris biobuffer for mild hydrocarboxylation of alkanes to carboxylic acids

The new tricopper(II) complex [Cu(3)(μ(3)-BO)(H(3)L)(3)][BF(4)]·2H(2)O (1) with an unprecedented diamondoid-like [Cu(3)B(μ-O)(6)] core has been easily generated by self-assembly in an aqueous medium from Cu(NO(3))(2), NaBF(4), NaOH and Bis-Tris (H(5)L) biobuffer, (HOCH(2))(3)CN(CH(2)CH(2)OH)(2). Compound 1 efficiently promotes the mild single-pot hydrocarboxylation, by CO and H(2)O, of various linear and cyclic C(n) (n = 2-8) alkanes into the corresponding C(n+1) carboxylic acids.     

A series of octanuclear-nickel(II) complexes supported by thiacalix[4]arenes

A series of discrete complexes, [Ni(8)(BTC4A)(2)(μ(6)-CO(3))(2)(μ-CH(3)COO)(4)(dma)(4)]·H(2)O (1), [Ni(8)(BTC4A)(2)(μ(6)-CO(3))(2)(μ-Cl)(2)(μ-HCOO)(2)(dma)(4)]·2DMF·2CH(3)CN (2), [Ni(8)(PTC4A)(2) (μ(6)-CO(3))(2)(μ-CH(3)COO)(4)(dma)(4)]·DMF (3), and [Ni(8)(PTC4A)(2)(μ(6)-CO(3))(2)(μ-OH)(μ-HCOO)(3) (dma)(4)] (4) (p-tert-butylthiacalix[4]arene = H(4)BTC4A, p-phenylthiacalix[4]arene = H(4)PTC4A, dma = dimethylamine, and DMF = N,N'-dimethylformamide), have been prepared under solvothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses, powder XRD, and IR spectroscopy. These four complexes are stacked by dumbbell-like building blocks with one chairlike octanuclear-nickel(II) core, which is capped by two thiacalix[4]arene molecules and connected by two in situ generated carbonato anions and different auxiliary anions. This work implied that not only the solvent molecules but also the upper-rim groups of thiacalix[4]arenes have significant effects on the self-assembly of the dumbbell-like building blocks. The magnetic properties of complexes 1-4 were examined, indicating strong antiferromagnetic interactions between the nickel(II) ions in the temperature range of 50-300 K.     

Dithiocarboxylate complexes of ruthenium(II) and osmium(II)

The ruthenium(II) complexes [Ru(R)(κ(2)-S(2)C·IPr)(CO)(PPh(3))(2)](+) (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C≡CPh)=CHPh) are formed on reaction of IPr·CS(2) with [Ru(R)Cl(CO)(BTD)(PPh(3))(2)] (BTD = 2,1,3-benzothiadiazole) or [Ru(C(C≡CPh)=CHPh)Cl(CO)(PPh(3))(2)] in the presence of ammonium hexafluorophosphate. Similarly, the complexes [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)](+) and [Ru(C(C≡CPh)=CHPh)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)](+) are formed in the same manner when ICy·CS(2) is employed. The ligand IMes·CS(2) reacts with [Ru(R)Cl(CO)(BTD)(PPh(3))(2)] to form the compounds [Ru(R)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C≡CPh)=CHPh). Two osmium analogues, [Os(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) and [Os(C(C≡CPh)=CHPh)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) were also prepared. When the more bulky diisopropylphenyl derivative IDip·CS(2) is used, an unusual product, [Ru(κ(2)-SC(H)S(CH=CHC(6)H(4)Me-4)·IDip)Cl(CO)(PPh(3))(2)](+), with a migrated vinyl group, is obtained. Over extended reaction times, [Ru(CH=CHC(6)H(4)Me-4)Cl(BTD)(CO)(PPh(3))(2)] also reacts with IMes·CS(2) and NH(4)PF(6) to yield the analogous product [Ru{κ(2)-SC(H)S(CH=CHC(6)H(4)Me-4)·IMes}Cl(CO)(PPh(3))(2)](+)via the intermediate [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+). Structural studies are reported for [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IPr)(CO)(PPh(3))(2)]PF(6) and [Ru(C(C≡CPh)=CHPh)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)]PF(6).     

Planar tetranuclear lanthanide clusters with the Dy4 analogue displaying slow magnetic relaxation

Two isostructural tetranuclear lanthanide clusters of general formula [Ln(III)(4)(μ(3)-OH)(2)(o-van)(4)(O(2)CC(CH(3))(3))(4)(NO(3))(2)]·CH(2)Cl(2)·1.5H(2)O (Ln = Gd (1) and Dy (2)) (o-van = 3-methoxysalicylaldehydato anion) are reported. The metallic cores of both complexes display a planar 'butterfly' arrangement. Magnetic studies show that both are weakly coupled, with 2 displaying probable SMM behaviour.     

Phenoxido and alkoxido-bridged dinuclear dysprosium complexes showing single-molecule magnet behaviour

Two new dysprosium(iii) complexes, [Dy(2)(HL(1))(4)(CO(3))]·4H(2)O (1) and [Dy(2)(L(2))(2)(NO(3))(2)(CH(3)OH)(2)]·4CH(3)CN (2), have been synthesized from the Schiff-base ligands N'-((2-hydroxy-1-naphthyl)methylene)benzohydrazide (H(2)L(1)) and N'-((2-hydroxy-1-naphthyl)methylene) picolinohydrazide (H(2)L(2)). Single-crystal X-ray diffraction studies reveal that four mono-deprotonated H(2)L(1) ligands and two di-deprotonated H(2)L(2) ligands which have undergone keto-enol tautomerism coordinate to the two dysprosium centres of complexes 1 and 2, respectively. The dc magnetic properties of complexes 1 and 2 are different. The phenoxido bridges in complex 1 mediate antiferromagnetic interaction between Dy(III) ions, while ferromagnetic interaction was clearly observed in alkoxido-bridged dinuclear complex 2. Furthermore, both complexes show frequency-dependent ac magnetic susceptibilities, indicating a slow relaxation of the magnetization, typical of SMM behaviour.     

Hybrid dibismuthines and distibines as ligands towards transition metal carbonyls

The hybrid dibismuthines O(CH(2)CH(2)BiPh(2))(2) and MeN(CH(2)-2-C(6)H(4)BiPh(2))(2) react with [M(CO)(5)(thf)] (M = Cr or W) to form [{M(CO)(5)}(2){O(CH(2)CH(2)BiPh(2))(2)}] and [{Cr(CO)(5)}(2){MeN(CH(2)-2-C(6)H(4)BiPh(2))(2)}] containing bridging bidentate (Bi(2)) coordination. The unsymmetrical tertiary bismuthine complexes [M(CO)(5){BiPh(2)(o-C(6)H(4)OMe)}] are also described. Depending upon the molar ratio, the hybrid distibines O(CH(2)CH(2)SbMe(2))(2) and MeN(CH(2)-2-C(6)H(4)SbMe(2))(2) react with [M(CO)(5)(thf)] to give the pentacarbonyl complexes [{M(CO)(5)}(2){O(CH(2)CH(2)SbMe(2))(2)}] and [{Cr(CO)(5)}(2){MeN(CH(2)-2-C(6)H(4)SbMe(2))(2)}] or tetracarbonyls cis-[M(CO)(4){O(CH(2)CH(2)SbMe(2))(2)}] and cis-[M(CO)(4){MeN(CH(2)-2-C(6)H(4)SbMe(2))(2)}]. The latter can also be obtained from [Cr(CO)(4)(nbd)] or [W(CO)(4)(pip)(2)], and contain chelating bidentates (Sb(2)-coordinated) as determined crystallographically. S(CH(2)-2-C(6)H(4)SbMe(2))(2) coordinates as a tridentate (SSb(2)) in fac-[M(CO)(3){S(CH(2)-2-C(6)H(4)SbMe(2))(2)}] (M = Cr or Mo) and fac-[Mn(CO)(3){S(CH(2)-2-C(6)H(4)SbMe(2))(2)}][CF(3)SO(3)]. Fac-[Mn(CO)(3){MeN(CH(2)-2-C(6)H(4)SbMe(2))(2)}][CF(3)SO(3)] contains NSb(2)-coordinated ligand in the solid state, but in solution a second species, Sb(2)-coordinated and with a κ(1)-CF(3)SO(3) replacing the coordinated amine is also evident. X-ray crystal structures were also determined for fac-[Cr(CO)(3){S(CH(2)-2-C(6)H(4)SbMe(2))(2)}], fac-[Mn(CO)(3){S(CH(2)-2-C(6)H(4)SbMe(2))(2)}][CF(3)SO(3)] and fac-[Mn(CO)(3){MeN(CH(2)-2-C(6)H(4)SbMe(2))(2)}] [CF(3)SO(3)]. Hypervalent N···Sb interactions are present in cis-[M(CO)(4){MeN(CH(2)-2-C(6)H(4)SbMe(2))(2)}] (M = Mo or W), but absent for M = Cr.     

Reactivity of TCNE or TCNQ derivatives of quinonoid zwitterions: platinum-induced HCN elimination vs oxidative-addition

The reaction of the functional, zwitterionic quinonoid molecule (6E)-4-(butylamino)-6-(butyliminio)-3-oxo-2-(1,1,2,2-tetracyanoethyl)cyclohexa-1,4-dien-1-olate, [C(6)H-2-{C(CN)(2)C(CN)(2)H}]-4,6-(···NH n-Bu)(2)-1,3(···O)(2) (2), which has been previously prepared by regioselective insertion of TCNE into the C-H bond adjacent to the C···O bonds of the zwitterionic benzoquinone monoimine (6E)-4-(butylamino)-6-(butyliminio)-3-oxocyclohexa-1,4-dien-1-olate, C(6)H(2)-4,6-(···NHn-Bu)(2)-1,3-(···O)(2) (1), with 2 equiv of [Pt(C(2)H(4))(PPh(3))(2)], afforded the Pt(0) complex [Pt(PPh(3))(2)(4)] (6) (4 = 2-HCN; (6E)-4-(butylamino)-6-(butyliminio)-3-oxo-2-(1,2,2-tricyanoethenyl)cyclohexa-1,4-dien-1-olate), in which a tricyanoethenyl moiety is π-bonded to the metal. A metal-induced HCN elimination reaction has thus taken place. The same complex was obtained directly by the reaction of 1 equiv of the Pt(0) complex [Pt(C(2)H(4))(PPh(3))(2)] with the olefinic ligand [C(6)H-2-{C(CN)═C(CN)(2)}]-4,6-(···NHn-Bu)(2)-1,3-(···O)(2)) (4), previously obtained by the reaction of 2 with NEt(3) in THF. A similar reactivity pattern was observed between 2 and 2 equiv of the Pd(0) precursor [Pd(dba)(2)] in the presence of dppe, which led to [Pd(dppe)(4)] (7), which was also directly obtained from 4 and 1 equiv [Pd(dba)(2)]/dppe. In contrast to the behavior of the TCNE derivative 2, the reaction of the TCNQ derivative (6E)-4-(butylamino)-6-(butyliminio)-2-(dicyano(4-(dicyanomethyl)phenyl)methyl)-3-oxocyclohexa-1,4-dien-1-olate, [C(6)H-2-{C(CN)(2)p-C(6)H(4)C(CN)(2)H}]-4,6-(···NHn-Bu)(2)-1,3-(···O)(2)) (3), with 2 equiv of [Pt(C(2)H(4))(PPh(3))(2)] led to formal oxidative-addition of the C-H bond of the C(CN)(2)H moiety to give the Pt(II) hydride complex trans-[PtH(PPh(3))(2){N═C═C(CN)p-C(6)H(4)C(CN)(2)-2-[C(6)H-4,6-(···NHn-Bu)(2)-1,3-(···O)(2))}] (8). The molecular structures of 3, 4, 6·0.5(H(2)O), and 8·3(CH(2)Cl(2)) have been determined by single-crystal X-ray diffraction.     

Porous anionic, cationic, and neutral metal-carboxylate frameworks constructed from flexible tetrapodal ligands: syntheses, structures, ion-exchanges, and magnetic properties

A series of coordination polymers with anionic, cationic, and neutral metal-carboxylate frameworks have been synthesized by using a flexible tetrapodal ligand tetrakis[4-(carboxyphenyl)oxamethyl] methane acid (H(4)X). The reactions between divalent transition-metal ions and H(4)X ligands gave [M(3)X(2)]·[NH(2)(CH(3))(2)](2)·8DMA (M = Co (1), Mn (2), Cd(3)) which have anionic metal-carboxylate frameworks with NH(2)(CH(3))(2)(+) cations filled in channels. The reactions of trivalent metal ions Y(III), Dy(III), and In(III) with H(4)X ligands afforded cationic metal-carboxylate frameworks [M(3)X(2)·(NO(3))·(DMA)(2)·(H(2)O)]·5DMA·2H(2)O (M = Y(4), Dy(5)) and [In(2)X·(OH)(2)]·3DMA·6H(2)O (6) with the NO(3)(-) and OH(-) serving as counterions, respectively. Moreover, a neutral metal-carboxylate framework [Pb(2)X·(DMA)(2)]·2DMA (7) can also be isolated from reaction of Pb(II) and H(4)X ligands. The charged metal-carboxylate frameworks 1-5 have selectivity for specific counterions in the reaction system, and compounds 1 and 2 display ion-exchange behavior. Moreover, magnetic property measurements on compounds 1, 2, and 5 indicate that there exists weak antiferromagnetic interactions between magnetic centers in the three compounds.     

Planar tetranuclear Dy(III) single-molecule magnet and its Sm(III), Gd(III), and Tb(III) analogues encapsulated by salen-type and β-diketonate ligands

The syntheses, structures, and magnetic properties are reported for four new lanthanide clusters [Sm(4)(μ(3)-OH)(2)L(2)(acac)(6)]·4H(2)O (1), [Gd(4)(μ(3)-OH)(2)L(2)(acac)(6)]·4CH(3)CN (2), and [Ln(4)(μ(3)-OH)(2)L(2)(acac)(6)]·2H(2)L·2CH(3)CN (3, Ln = Tb; 4, Ln = Dy) supported by salen-type (H(2)L = N,N'-bis(salicylidene)-1,2-cyclohexanediamine) and β-diketonate (acac = acetylacetonate) ligands. The four clusters were confirmed to be essentially isomorphous by infrared spectroscopy and single-crystal X-ray diffraction. Their crystal structures reveal that the salen-type ligand provides a suitable tetradentate coordination pocket (N(2)O(2)) to encapsulate lanthanide(III) ions. Moreover, the planar Ln(4) core is bridged by two μ(3)-hydroxide, four phenoxide, and two ketonate oxygen atoms. Magnetic properties of all four compounds have been investigated using dc and ac susceptibility measurements. For 4, the static and dynamic data indicate that the Dy(4) complex exhibits slow relaxation of the magnetization below 5 K associated with single-molecule magnet behavior.     

Nitrate-Bridged "Pseudo-Double-Propeller"-Type Lanthanide(III)-Copper(II) Heterometallic Clusters: Syntheses, Structures, and Magnetic Properties

Two discrete nitrate-bridged novel "pseudo-double-propeller"-shaped hexanuclear Cu/Ln clusters of the formula [Cu(4)Ln(2)L(4)L'(4)(NO(3))(2)(OH(2))(2)]·3NO(3)·4H(2)O [Ln = Dy, Gd; LH = o-vanilin; L'H = 2-(hydroxyethyl)pyridine] were synthesized and characterized. Single-crystal X-ray diffraction studies revealed the trimeric half-propeller-type Cu(2)/Ln core connected to other opposite-handed similar trimers by a bridging nitrate ligand. The Dy analogue, [Cu(4)Dy(2)L(4)L'(4)(NO(3))(2)(OH(2))(2)]·3NO(3)·4H(2)O, shows frequency-dependent out-of-phase alternating-current magnetic susceptibility, which indicates that this novel discrete [Cu(4)Dy(2)] heterometallic cluster may exhibit single-molecule-magnet behavior.     

Syntheses, structures and properties of a series of non-heme alkoxide-Fe(III) complexes of a benzimidazolyl-rich ligand as models for lipoxygenase

The treatment of Fe(ClO(4))(2)·6H(2)O or Fe(ClO(4))(3)·9H(2)O with a benzimidazolyl-rich ligand, N,N,N',N'-tetrakis[(1-methyl-2-benzimidazolyl)methyl]-1,2-ethanediamine (medtb) in alcohol/MeCN gives a mononuclear ferrous complex, [Fe(II)(medtb)](ClO(4))(2)·?CH(3)CN·?CH(3)OH (1), and four non-heme alkoxide-iron(III) complexes, [Fe(III)(OMe)(medtb)](ClO(4))(2)·H(2)O (2, alcohol = MeOH), [Fe(III)(OEt)(Hmedtb)](ClO(4))(3)·CH(3)CN (3, alcohol = EtOH), [Fe(III)(O(n)Pr)(Hmedtb)](ClO(4))(3)·(n)PrOH·2CH(3)CN (4, alcohol = n-PrOH), and [Fe(III)(O(n)Bu)(Hmedtb)](ClO(4))(3)·3CH(3)CN·H(2)O (5, alcohol = n-BuOH), respectively. The alkoxide-iron(III) complexes all show 1) a Fe(III)-OR center (R = Me, 2; Et, 3; (n)Pr, 4; (n)Bu, 5) with the Fe-O bond distances in the range of 1.781-1.816 ?, and 2) a yellow color and an intense electronic transition around 370 nm. The alkoxide-iron(III) complexes can be reduced by organic compounds with a cis,cis-1,4-diene moiety via the hydrogen atom abstraction reaction.     

Syntheses of 8-quinolinolatocobalt(III) complexes containing cyclen based auxiliary ligands as models for hypoxia-activated prodrugs

New ligands H(2)L2-H(2)L6 comprise the cyclen macrocycle which is N,N'-dialkylated at the 1,7-nitrogen atoms by three- and four-carbon alkyl chains bearing terminal sulfonic (C(3) H(2)L2), phosphonic (C(3) H(2)L3, C(4) H(2)L4) or carboxylic acid (C(3) H(2)L5, C(4) H(2)L6) groups, and HL7 is N-monoalkylated by a four-carbon sulfonic acid group. The ligands were prepared by alkylation of a bridged bisaminal intermediate. The syntheses of cobalt(III) complexes containing a tetradentate cyclen, N,N'-1,7-Me(2)cyclen, cyclam or L2-L7 ligand together with the bidentate 8-quinolinato (8QO(-)) ligand, of interest as it is a model for a more potent cytotoxic analogue, were investigated. Coordination of ligands (L) cyclen, N,N'-1,7-Me(2)cyclen or cyclam to cobalt(III) was achieved using Na(3)[Co(NO(6))] to form [Co(L)(NO(2))(2)](+). HOTf (trifluoromethansulfonic acid) was used to prepare the triflato complexes [Co(L)(OTf)(2)](+), followed by substitution of the labile triflato ligands to yield [Co(L)(8QO)](ClO(4))(2) isolated as the perchlorate salts. One further example containing cyclam and the 5-hydroxymethyl-8-quinolinato ligand was also prepared by this method. Complexes containing the pendant arm ligands L2-L6 were prepared from the cobalt precursor trans-[Co(py)(4)Cl(2)](+). Reaction of this complex with H(2)L2·4HCl and 8QOH produced [Co(L2)(8QO)] in one step and contains two deprotonated sulfonato pendant arms. The reaction of H(2)L3·4HBr with [Co(py)(4)Cl(2)](+) gave [Co(L3)]Cl in which L3 acts as a hexadenate ligand with the three-carbon phosphonato side chains coordinated to cobalt. H(2)L5·4HCl bearing three-carbon carboxylic acid pendant arms gave a similar result. The four-carbon ligands were coordinated to cobalt by reaction of [Co(py)(4)Cl(2)](+) with H(2)L4·4HBr or H(2)L6·4HCl to give [Co(HL4)Cl(2)] or [Co(H(2)L6)Cl(2)]Cl, which in turn with 8QOH gave the 8QO(-) complexes [Co(L4)(8QO)] bearing anionic phosphate pendant arms or [Co(H(2)L6)(8QO)]Cl(2) containing neutral carboxylic acid side chains. The reaction of Na(3)[Co(CO(3))(3)] with the mono-N-alkylated ligand HL7·4HCl and then HOTf gave [Co(L7)(CO(3))] and then in turn [Co(L7)(OTf)(2)]. The carbonato complex [Co(L7)(CO(3))] with [8QO](2)[SO(4)] produced [Co(L7)(CO(3))]. All complexes containing L7 bear an anionic sulfonato group on the side chain. The synthesis and characterisation of the six new ligands based on N-alkylated cylen ligand and the cobalt complexes outlined above are described, along with cyclic voltammograms of the 8QO(-) complexes and the molecular structures determined by X-ray crystallography of [Co(cyclen)(H(2)O)(2)](OTf)(3) (formed by aquation of the triflato complex), [Co(cyclen)(8QO)](ClO(4))(2), Co(L2)(8QO)·2H(2)O, Co(L4)(8QO)·6H(2)O and [Co(H(2)L6)Cl(2)]Cl·H(2)O. These demonstrate the coordination of the cyclen ligand in the folded anti-O,syn-N configuration with the N-alkylated nitrogens occupying apical positions.     

Di- and tetra-nuclear copper(II), nickel(II), and cobalt(II) complexes of four bis-tetradentate triazole-based ligands: synthesis, structure, and magnetic properties

Four bis-tetradentate N(4)-substituted-3,5-{bis[bis-N-(2-pyridinemethyl)]aminomethyl}-4H-1,2,4-triazole ligands, L(Tz1)-L(Tz4), differing only in the triazole N(4) substituent R (where R is amino, pyrrolyl, phenyl, or 4-tertbutylphenyl, respectively) have been synthesized, characterized, and reacted with M(II)(BF(4))(2)·6H(2)O (M(II) = Cu, Ni or Co) and Co(SCN)(2). Experiments using all 16 possible combinations of metal salt and L(TzR) were carried out: 14 pure complexes were obtained, 11 of which are dinuclear, while the other three are tetranuclear. The dinuclear complexes include two copper(II) complexes, [Cu(II)(2)(L(Tz2))(H(2)O)(4)](BF(4))(4) (2), [Cu(II)(2)(L(Tz4))(BF(4))(2)](BF(4))(2) (4); two nickel(II) complexes, [Ni(II)(2)(L(Tz1))(H(2)O)(3)(CH(3)CN)](BF(4))(4)·0.5(CH(3)CN) (5) and [Ni(II)(2)(L(Tz4))(H(2)O)(4)](BF(4))(4)·H(2)O (8); and seven cobalt(II) complexes, [Co(II)(2)(L(Tz1))(μ-BF(4))](BF(4))(3)·H(2)O (9), [Co(II)(2)(L(Tz2))(μ-BF(4))](BF(4))(3)·2H(2)O (10), [Co(II)(2)(L(Tz3))(H(2)O)(2)](BF(4))(4) (11), [Co(II)(2)(L(Tz4))(μ-BF(4))](BF(4))(3)·3H(2)O (12), [Co(II)(2)(L(Tz1))(SCN)(4)]·3H(2)O (13), [Co(II)(2)(L(Tz2))(SCN)(4)]·2H(2)O (14), and [Co(II)(2)(L(Tz3))(SCN)(4)]·H(2)O (15). The tetranuclear complexes are [Cu(II)(4)(L(Tz1))(2)(H(2)O)(2)(BF(4))(2)](BF(4))(6) (1), [Cu(II)(4)(L(Tz3))(2)(H(2)O)(2)(μ-F)(2)](BF(4))(6)·0.5H(2)O (3), and [Ni(II)(4)(L(Tz3))(2)(H(2)O)(4)(μ-F(2))](BF(4))(6)·6.5H(2)O (7). Single crystal X-ray structure determinations revealed different solvent content from that found by microanalysis of the bulk sample after drying under a vacuum and confirmed that 5', 8', 9', 11', 12', and 15' are dinuclear while 1' and 7' are tetranuclear. As expected, magnetic measurements showed that weak antiferromagnetic intracomplex interactions are present in 1, 2, 4, 7, and 8, stabilizing a singlet spin ground state. All seven of the dinuclear cobalt(II) complexes, 9-15, have similar magnetic behavior and remain in the [HS-HS] state between 300 and 1.8 K.     

Synthesis and coordination chemistry of phosphine oxide decorated dibenzofuran platforms

A four-step synthesis for 4,6-bis(diphenylphosphinoylmethyl)dibenzofuran (4) from dibenzofuran and a two-step synthesis for 4,6-bis(diphenylphosphinoyl)dibenzofuran (5) are reported along with coordination chemistry of 4 with In(III), La(III), Pr(III), Nd(III), Er(III), and Pu(IV) and of 5 with Er(III). Crystal structure determinations for the ligands, 4·CH(3)OH and 5, the 1:1 complexes [In(4)(NO(3))(3)], [Pr(4)(NO(3))(3)(CH(3)CN)]·0.5CH(3)CN, [Er(4)(NO(3))(3)(CH(3)CN)]·CH(3)CN, [Pu(4)Cl(4)]·THF and the 2:1 complex [Nd(4)(2)(NO(3))(2)](2)(NO(3))(2)·(H(2)O)·4(CH(3)OH) are described. In these complexes, ligand 4 coordinates in a bidentate POP'O' mode via the two phosphine oxide O-atoms. The dibenzofuran ring O-atom points toward the central metal cations, but in every case it is more than 4 ? from the metal. A similar bidentate POP'O' chelate structure is formed between 5 and Er(III) in the complex, {[Er(5)(2)(NO(3))(2)](NO(3))·4(CH(3)OH)}(0.5), although the nonbonded Er···O(furan) distance is reduced to ～3.6 ?. The observed bidentate chelation modes for 4 and 5 are consistent with results from molecular mechanics computations. The solvent extraction performance of 4 and 5 in 1,2-dichloroethane for Eu(III) and Am(III) in nitric acid solutions is described and compared against the extraction behavior of n-octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (OΦDiBCMPO) measured under identical conditions.     

Dodecanuclear manganese(III) phosphonates with cage structures

Treatments of Mn(O(2)CR)(2) (R = Me, Ph) with NBu(4)MnO(4) in CH(3)CN or CH(3)CN/CH(2)Cl(2) in the presence of acetic acid, delta(1)-cyclohexenephosphonic acid (C(6)H(9)PO(3)H(2)), and 2,2'-bipyridine or 1,10-phenanthroline result in three novel dodecamanganese(III) clusters [Mn(12)O(8)(O(2)CMe)(6)(O(3)PC(6)H(9))(7)(bipy)(3)] (1), [Mn(12)O(8)(O(2)CPh)(6)(O(3)PC(6)H(9))(7)(bipy)(3)] (2), and [Mn(12)O(8)(O(2)CPh)(6)(O(3)PC(6)H(9))(7)(phen)(3)] (3). They have a similar Mn(12) core of [Mn(III)(12)(mu(4)-O)(3)(mu(3)-O)(5)(mu-O(3)P)(3)] with a new type of topologic structure. Solid-state dc magnetic susceptibility measurements of complexes 1-3 reveal that dominant antiferromagnetic interactions are propagated between the magnetic centers. The ac magnetic measurements suggest an S = 2 ground state for compounds 1 and 3 and an S = 3 ground state for compound 2.     

S(T) = 22 [Mn10] supertetrahedral building-block to design extended magnetic networks

The controlled organization of high-spin complexes, eventually single-molecule magnets, is a great challenge in molecular sciences to probe the possibility to design sophisticated magnetic systems to address a large quantity of magnetic information. The coordination chemistry is a tool of choice to make such materials. In this work, high-spin S(T) = 22 [Mn(10)] complexes, such as [Mn(III)(6)Mn(II)(4)(L(1))(6)(μ(4)-O)(4)(μ(3)-N(3))(4)(CH(3)CN)(11)(H(2)O)]·(ClO(4))(2)·(CH(3)CN)(8.5) (1), have been assembled using (i) 1,3-propanediol derivatives as chelating ligands to form the [Mn(10)] core units and (ii) dicyanamide or azide anions as linkers to synthesize the first 2D and 3D [Mn(10)]-based networks: [Mn(III)(6)Mn(II)(4)(L(2))(6)(μ(3)-N(3))(4)(μ(4)-O)(4)(CH(3)OH)(4)(dca)(2)] (2) and [Mn(III)(6)Mn(II)(4)(L(3))(6)(μ(3)-N(3))(4)(μ(4)-O)(4)(N(3))(2)]·(CH(3)OH)(4) (3). The synthesis of these compounds is reported together with their single-crystal X-ray structures and magnetic properties supported by DFT calculations. In the reported synthetic conditions, the stability of the [Mn(10)] complex is remarkably good that allows us to imagine many new materials combining these high-spin moieties and other diamagnetic but also paramagnetic linkers to design for example ordered magnets.