Chiral Single-Chain Magnet: Helically Stacked [Mn^III₂Cu^II] Triangles

The one-dimensional complex [Mn^III₂Cu^II(μ₃-O)­(Cl-sao)₃(EtOH)₂]·EtOH (Mn₂Cu) was obtained by the metal replacement reaction of the trinuclear manganese complex (Et₃NH)­[Mn^III₃(μ₃-O)­Cl₂(Cl-sao)₃(MeOH)₂(H₂O)₂] with [Cu­(acac)₂]. The Mn₂Cu chain exhibits single-chain-magnet behavior with finite-size effects due to its large magnetic anisotropy

Enneanuclear [Ni₆Ln₃] Cages: [Ln^III₃] Triangles Capping [Ni^II₆] Trigonal Prisms Including a [Ni₆Dy₃] Single-Molecule Magnet

The use of (2-(β-naphthalideneamino)-2-hydroxymethyl-1-propanol) ligand, H₃L, in Ni/Ln chemistry has led to the isolation of three new isostructural [Ni^II₆Ln^III₃] metallic cages. More specifically, the reaction of Ni­(ClO₄)₂·6H₂O, the corresponding lanthanide nitrate salt, and H₃L in MeCN, under solvothermal conditions in the presence of NEt₃, led to the isolation of three complexes with the formulas [Ni₆Gd₃(OH)₆(HL)₆(NO₃)₃]·5.75MeCN·2Et₂O·1.5H₂O (<b>1</b>·5.75MeCN·2Et₂O·1.5H₂O), [Ni₆Dy₃(OH)₆(HL)₆(NO₃)₃]·2MeCN·2.7Et₂O·2.4H₂O (<b>2</b>·2MeCN·2.7Et₂O·2.4H₂O), and [Ni₆Er₃(OH)₆(HL)₆(NO₃)₃]·5.75MeCN·2Et₂O·1.5H₂O (<b>3</b>·5.75MeCN·2Et₂O·1.5H₂O). The structure of all three clusters describes a [Ln^III₃] triangle capping a [Ni^II₆] trigonal prism. Direct current magnetic susceptibility studies in the 5–300 K range for complexes <b>1</b>–<b>3</b> reveal the different nature of the magnetic interactions within the clusters: dominant antiferromagnetic exchange interactions for the Dy^III and Er^III analogues and dominant ferromagnetic interactions for the Gd^III example. Alternating current magnetic susceptibility measurements under zero external dc field displayed fully formed temperature- and frequency-dependent out-of-phase peaks for the [Ni^II₆Dy^III₃] analogue, establishing its single molecule magnetism behavior with <i>U</i>_eff = 24 K

Enneanuclear [Ni₆Ln₃] Cages: [Ln^III₃] Triangles Capping [Ni^II₆] Trigonal Prisms Including a [Ni₆Dy₃] Single-Molecule Magnet

The use of (2-(β-naphthalideneamino)-2-hydroxymethyl-1-propanol) ligand, H₃L, in Ni/Ln chemistry has led to the isolation of three new isostructural [Ni^II₆Ln^III₃] metallic cages. More specifically, the reaction of Ni­(ClO₄)₂·6H₂O, the corresponding lanthanide nitrate salt, and H₃L in MeCN, under solvothermal conditions in the presence of NEt₃, led to the isolation of three complexes with the formulas [Ni₆Gd₃(OH)₆(HL)₆(NO₃)₃]·5.75MeCN·2Et₂O·1.5H₂O (<b>1</b>·5.75MeCN·2Et₂O·1.5H₂O), [Ni₆Dy₃(OH)₆(HL)₆(NO₃)₃]·2MeCN·2.7Et₂O·2.4H₂O (<b>2</b>·2MeCN·2.7Et₂O·2.4H₂O), and [Ni₆Er₃(OH)₆(HL)₆(NO₃)₃]·5.75MeCN·2Et₂O·1.5H₂O (<b>3</b>·5.75MeCN·2Et₂O·1.5H₂O). The structure of all three clusters describes a [Ln^III₃] triangle capping a [Ni^II₆] trigonal prism. Direct current magnetic susceptibility studies in the 5–300 K range for complexes <b>1</b>–<b>3</b> reveal the different nature of the magnetic interactions within the clusters: dominant antiferromagnetic exchange interactions for the Dy^III and Er^III analogues and dominant ferromagnetic interactions for the Gd^III example. Alternating current magnetic susceptibility measurements under zero external dc field displayed fully formed temperature- and frequency-dependent out-of-phase peaks for the [Ni^II₆Dy^III₃] analogue, establishing its single molecule magnetism behavior with <i>U</i>_eff = 24 K

A family of hexanuclear Mn(III) single-molecule magnets

<div><p>In an attempt to employ salicylic acid (HOsalH), 2,6-dihydroxy benzoic acid {(HO)₂PhCO₂H}, and naphthalene-1,8-dicarboxylic acid {1,8-naph(CO₂H)₂} in Mn(III) salicylaldoximate chemistry as a means to alter the structural identity of the hexanucluear clusters usually obtained from this reaction system, we have isolated a family of hexanuclear Mn(III) complexes based on salicyladloxime (saoH₂) and 2-hydroxy-1-naphthaldehyde oxime (naphthsaoH₂). Five hexanuclear clusters, [Mn₆O₂(sao)₆(HOsal)₂(EtOH)₄]·EtOH (<b>1</b>·EtOH), [Mn₆O₂(sao)₆{1,8-naph(CO₂Me)(CO₂)}₂(MeOH)₆]·3MeOH (<b>2</b>·3MeOH), [Mn₆O₂(naphthsao)₆{1,8-naph(CO₂Et)(CO₂)}₂(EtOH)₆] (<b>3</b>·2MeOH), [Mn₆O₂(naphthsao)₆(MeCO₂)₂(EtOH)₄]·2H₂O (<b>4</b>·2H₂O), and [Mn₆O₂(naphthsao)₆{(HO)₂PhCO₂}₂(EtOH)₄]·4EtOH (<b>5</b>·4EtOH), have been synthesized and characterized by single-crystal X-ray crystallography. The magnetic properties of <b>3</b>, <b>4</b>, and <b>5</b> are discussed.</p></div

Supramolecular Entanglement from Interlocked Molecular Nanomagnets

The trinuclear nanomagnet [MnIII3O(Et-sao)3(MeOH)3](ClO4) (1) has been utilized as a building block for the construction of the hexanuclear cluster [{MnIII3O(Et-sao)3(O2CPh)(EtOH)}2{4,4′-bpe}2] (3) that conforms to a rectangle and the two-dimensional coordination polymer {[MnIII3O(sao)3(4,4′-bpe)1.5]ClO4·3MeOH}n (2·3MeOH). The latter exhibits an unprecedented type of entanglement that is based on host guest interactions. The polygon versus the polymer is rationalized in terms of changing an auxiliary anion that influences the arrangement of the potentially “vacant” coordination axes on each MnIII ion of the trinuclear precursor and thereby directing the self-assembly process

Toward a Magnetostructural Correlation for a Family of Mn₆ SMMs

We have structurally and magnetically characterized a total of 12 complexes based on the Single-Molecule Magnet (SMM) [MnIII6O2(sao)6(O2CH)2(MeOH) 4] (1) (where sao2- is the dianion of salicylaldoxime or 2-hydroxybenzaldeyhyde oxime) that display analogous structural cores but remarkably different magnetic behaviors. Via the use of derivatized oxime ligands and bulky carboxylates we show that it is possible to deliberately increase the value of the spin ground state of the complexes [Mn6O2(Me-sao)6(O2CCPh3)2(EtOH)4] (2), [Mn6O2(Et-sao)6(O2CCMe3)2(EtOH)5] (3), [Mn6O2(Et-sao)6(O2CPh2OPh)2(EtOH)4] (4), [Mn6O2(Et-sao)6(O2CPh4OPh)2(EtOH)4(H2O)2] (5), [Mn6O2(Me-sao)6(O2CPhBr)2(EtOH)6] (6), [Mn6O2(Et-sao)6(O2CPh)2(EtOH)4(H2O)2] (7), [Mn6O2(Et-sao)6{O2CPh(Me)2}2(EtOH)6] (8), [Mn6O2(Et-sao)6(O2C11H15)2(EtOH)6] (9), [Mn6O2(Me-sao)6(O2C-th)2(EtOH)4(H2O)2] (10), [Mn6O2(Et-sao)6(O2CPhMe)2(EtOH)4(H2O)2] (11), and [Mn6O2(Et-sao)6(O2C12H17)2(EtOH)4(H2O)2] (12) (Et-saoH2 = 2-hydroxypropiophenone oxime, Me-saoH2 = 2-hydroxyethanone oxime, HO2CCPh3 = triphenylacetic acid, HO2CCMe3 = pivalic acid, HO2CPh2OPh = 2-phenoxybenzoic acid, HO2CPh4OPh = 4-phenoxybenzoic acid, HO2CPhBr = 4-bromobenzoic acid, HO2CPh(Me)2 = 3,5-dimethylbenzoic acid, HO2C11H15 = adamantane carboxylic acid, HO2C-th = 3-thiophene carboxylic acid, HO2CPhMe = 4-methylbenzoic acid, and HO2C12H17 = adamantane acetic acid) in a stepwise fashion from S = 4 to S = 12 and, in-so-doing, enhance the energy barrier for magnetization reorientation to record levels. The change from antiferromagnetic to ferromagnetic exchange stems from the “twisting” or “puckering” of the (−Mn−N−O−)3 ring, as evidenced by the changes in the Mn−N−O−Mn torsion angles

Toward a Magnetostructural Correlation for a Family of Mn₆ SMMs

We have structurally and magnetically characterized a total of 12 complexes based on the Single-Molecule Magnet (SMM) [MnIII6O2(sao)6(O2CH)2(MeOH) 4] (1) (where sao2- is the dianion of salicylaldoxime or 2-hydroxybenzaldeyhyde oxime) that display analogous structural cores but remarkably different magnetic behaviors. Via the use of derivatized oxime ligands and bulky carboxylates we show that it is possible to deliberately increase the value of the spin ground state of the complexes [Mn6O2(Me-sao)6(O2CCPh3)2(EtOH)4] (2), [Mn6O2(Et-sao)6(O2CCMe3)2(EtOH)5] (3), [Mn6O2(Et-sao)6(O2CPh2OPh)2(EtOH)4] (4), [Mn6O2(Et-sao)6(O2CPh4OPh)2(EtOH)4(H2O)2] (5), [Mn6O2(Me-sao)6(O2CPhBr)2(EtOH)6] (6), [Mn6O2(Et-sao)6(O2CPh)2(EtOH)4(H2O)2] (7), [Mn6O2(Et-sao)6{O2CPh(Me)2}2(EtOH)6] (8), [Mn6O2(Et-sao)6(O2C11H15)2(EtOH)6] (9), [Mn6O2(Me-sao)6(O2C-th)2(EtOH)4(H2O)2] (10), [Mn6O2(Et-sao)6(O2CPhMe)2(EtOH)4(H2O)2] (11), and [Mn6O2(Et-sao)6(O2C12H17)2(EtOH)4(H2O)2] (12) (Et-saoH2 = 2-hydroxypropiophenone oxime, Me-saoH2 = 2-hydroxyethanone oxime, HO2CCPh3 = triphenylacetic acid, HO2CCMe3 = pivalic acid, HO2CPh2OPh = 2-phenoxybenzoic acid, HO2CPh4OPh = 4-phenoxybenzoic acid, HO2CPhBr = 4-bromobenzoic acid, HO2CPh(Me)2 = 3,5-dimethylbenzoic acid, HO2C11H15 = adamantane carboxylic acid, HO2C-th = 3-thiophene carboxylic acid, HO2CPhMe = 4-methylbenzoic acid, and HO2C12H17 = adamantane acetic acid) in a stepwise fashion from S = 4 to S = 12 and, in-so-doing, enhance the energy barrier for magnetization reorientation to record levels. The change from antiferromagnetic to ferromagnetic exchange stems from the “twisting” or “puckering” of the (−Mn−N−O−)3 ring, as evidenced by the changes in the Mn−N−O−Mn torsion angles

Asymmetric [2+2+1] cyclopentannulation of olefins. Ring expansion of 2-N-methyl-N-tosyl-cyclobutanone

alpha-N-Methyl-N-tosyl cyclobutanones 2 which had been previously prepared in good yields and high enantiomeric excesses from olefins and chiral keteniminium salts have been converted into the corresponding oxiranes 3 by reaction with dimethylsulfonium methylid. The stereochemistry of this reaction was found to be dependent on several factors which have been analyzed. Treatment of these oxiranes with a stoichiometric amount of lithium iodide in refluxing tetrahydrofuran gave excellent yields of monocyclic or fused cyclopentenones 4 resulting from a P-elimination of N-methyl-N-tosylamide from a primarily formed cyclopentanone. The ring-expansion was totally selective but for oxiranes attached to a bicyclo[4.2.0]octanone system. In all cases, the enantiomeric purities of the starting cyclobutanones were preserved throughout the sequence which thus represents a useful [2+2+1] strategy for the cyclopentannulation of olefins. (C) 2002 Elsevier Science Ltd. All rights reserved

Rare Oxidation-State Combinations and Unusual Structural Motifs in Hexanuclear Mn Complexes Using 2-Pyridyloximate Ligands

The use of phenyl-2-pyridyl ketone oxime and di-2-pyridyl ketone oxime in Mn chemistry has led to hexanuclear clusters with unprecedented (MnII4MnIIIMnIV) or extremely rare (MnIIMnIII5 and MnII3MnIII3) metal oxidation-state combinations and uncommon structural motifs

Rare Oxidation-State Combinations and Unusual Structural Motifs in Hexanuclear Mn Complexes Using 2-Pyridyloximate Ligands

The use of phenyl-2-pyridyl ketone oxime and di-2-pyridyl ketone oxime in Mn chemistry has led to hexanuclear clusters with unprecedented (MnII4MnIIIMnIV) or extremely rare (MnIIMnIII5 and MnII3MnIII3) metal oxidation-state combinations and uncommon structural motifs