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

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

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