Artificial Amino Acids in Nickel(II) and Nickel(II)/Lanthanide(III) Chemistry

The synthesis and magnetic properties of five new homo- and heterometallic nickel(II) complexes containing artificial amino acids are reported: [Ni4(aib)3(aibH)3(NO3)](NO3)4·3.05MeOH (1·3.05MeOH), [Ni6La(aib)12](NO3)3·5.5H2O (2·5.5H2O), [Ni6Pr(aib)12](NO3)3·5.5H2O (3·5.5H2O), [Ni5(OH)2(l-aba)4(OAc)4]·0.4EtOH·0.3H2O 6(4·0.4EtOH·0.3H2O), and [Ni6La(l-aba)12][La2(NO3)9] (5; aibH = 2-aminoisobutyric acid; l-abaH = l-2-aminobutyric acid). Complexes 1 and 4 describe trigonal-pyramidal and square-based pyramidal metallic clusters, respectively, while complexes 2, 3, and 5 can be considered to be metallocryptand-encapsulated lanthanides. Complexes 4 and 5 are chiral and crystallize in the space groups I222 and P213, respectively. Direct-current magnetic susceptibility studies in the 2–300 K range for all complexes reveal the presence of dominant antiferromagnetic exchange interactions, leading to small or diamagnetic ground states

New members of the [Mn₆/oxime] family and analogues with converging [Mn₃] planes

<p>The synthesis, structural, and magnetic characterization of five new members of the hexanuclear oximate [Mn^III₆] family are reported. All five clusters can be described with the general formula [Mn^III₆O₂(R-sao)₆(R′-CO₂)₂(sol)_x(H₂O)_y] (where R-saoH₂ = salicylaldoxime substituted at the oxime carbon with R = H, Me and Et; R′ = 1-naphthalene, 2-naphthalene, and 1-pyrene; sol = MeOH, EtOH, or MeCN; <i>x</i> = 0–4 and <i>y</i> = 0–4). More specifically, the reaction of Mn(ClO₄)₂·6H₂O with salicylaldoxime-like ligands and the appropriate carboxylic acid in alcoholic or MeCN solutions in the presence of base afforded complexes <b>1</b>–<b>5</b>: [Mn₆O₂(Me-sao)₆(1-naphth-CO₂)₂(H₂O)(MeCN)]·4MeCN (<b>1</b>·4MeCN); [Mn₆O₂(Me-sao)₆(2-naphth-CO₂)₂(H₂O)(MeCN)]·3MeCN·0.1H₂O (<b>2</b>·3MeCN·0.1H₂O); [Mn₆O₂(Et-sao)₆(2-naphth-CO₂)₂(EtOH)₄(H₂O)₂] (<b>3</b>); [Mn₆O₂(Et-sao)₆(2-naphth-CO₂)₂(MeOH)₆] (<b>4</b>) and [Mn₆O₂(sao)₆(1-pyrene-CO₂)₂(H₂O)₂(EtOH)₂]·6EtOH (<b>5</b>·6EtOH). Clusters <b>3</b>, <b>4,</b> and <b>5</b> display the usual [Mn₆/oximate] structural motif consisting of two [Mn₃O] subunits bridged by two O_oximate atoms from two R-sao²⁻ ligands to form the hexanuclear complex in which the two triangular [Mn₃] units are parallel to each other. On the contrary, clusters <b>1</b> and <b>2</b> display a highly distorted stacking arrangement of the two [Mn₃] subunits resulting in two converging planes, forming a novel motif in the [Mn₆] family. Investigation of the magnetic properties for all complexes reveal dominant antiferromagnetic interactions for <b>1</b>, <b>2,</b> and <b>5</b>, while <b>3</b> and <b>4</b> display dominant ferromagnetic interactions with a ground state of <i>S</i> = 12 for both clusters. Finally, <b>3</b> and <b>4</b> display single-molecule magnet behavior with <i>U</i>_eff = 63 and 36 K, respectively.</p

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

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^II₄(aib)₃(aibH)₃(NO₃)]­(NO₃)₄·2.8CH₃OH·0.2H₂O (<b>1</b>·2.8CH₃OH·0.2H₂O), {Na₂[Co^II₂(aib)₂(N₃)₄(CH₃OH)₄]}_<i>n</i> (<b>2</b>), [Co^II₆La^III(aib)₆(OH)₃(NO₃)₂(H₂O)₄(CH₃CN)₂]·0.5­[La­(NO₃)₆]·0.75­(ClO₄)·1.75­(NO₃)·3.2CH₃CN·5.9H₂O (<b>3</b>·3.2CH₃CN·5.9H₂O), [Co^II₆Pr^III(aib)₆(OH)₃(NO₃)₃(CH₃CN)₆]·[Pr­(NO₃)₅]·0.41­[Pr­(NO₃)₃(ClO₄)_0.5(H₂O)_1.5]·0.59­[Co­(NO₃)₃(H₂O)]·0.2­(ClO₄)·0.25H₂O (<b>4</b>·0.25H₂O), [Co^II₆Nd^III(aib)₆(OH)₃(NO₃)_2.8(CH₃OH)_4.7(H₂O)_1.5]·2.7­(ClO₄)·0.5­(NO₃)·2.26CH₃OH·0.24H₂O (<b>5</b>·2.26CH₃OH·0.24H₂O), [Co^II₆Sm^III(aib)₆(OH)₃(NO₃)₃(CH₃CN)₆]·[Sm­(NO₃)₅]·0.44­[Sm­(NO₃)₃(ClO₄)_0.5(H₂O)_1.5]·0.56­[Co­(NO₃)₃(H₂O)]·0.22­(ClO₄)·0.3H₂O (<b>6</b>·0.3H₂O), [Co^II₆Eu^III(aib)₆(OH)₃(NO₃)₃(CH₃OH)_4.87(H₂O)_1.13]­(ClO₄)_2.5(NO₃)_0.5·2.43CH₃OH·0.92H₂O (<b>7</b>·2.43CH₃OH·0.92H₂O), [Co^II₆Gd^III(aib)₆(OH)₃(NO₃)_2.9(CH₃OH)_4.9(H₂O)_1.2]·2.6­(ClO₄)·0.5­(NO₃)·2.58CH₃OH·0.47H₂O (<b>8</b>·2.58CH₃OH·0.47H₂O), [Co^II₆Tb^III(aib)₆(OH)₃(NO₃)₃(CH₃CN)₆]·[Tb­(NO₃)₅]·0.034­[Tb­(NO₃)₃(ClO₄)_0.5(H₂O)_0.5]·0.656­[Co­(NO₃)₃(H₂O)]·0.343­(ClO₄)·0.3H₂O (<b>9</b>·0.3H₂O), [Co^II₆Dy^III(aib)₆(OH)₃(NO₃)_2.9(CH₃OH)_4.92(H₂O)_1.18]­(ClO₄)_2.6(NO₃)_0.5·2.5CH₃OH·0.5H₂O (<b>10</b>·2.5CH₃OH·0.5H₂O), [Co^II₆Ho^III(aib)₆(OH)₃(NO₃)₃(CH₃CN)₆]·0.27­[Ho­(NO₃)₃(ClO₄)_0.35(H₂O)_0.15]·0.656­[Co­(NO₃)₃(H₂O)]·0.171­(ClO₄) (<b>11</b>), [Co^II₆Er^III(aib)₆(OH)₄(NO₃)₂(CH₃CN)_2.5(H₂O)_3.5]­(ClO₄)₃·CH₃CN·0.75H₂O (<b>12</b>·CH₃CN·0.75H₂O), and [Co^II₆Tm^III(aib)₆(OH)₃(NO₃)₃(H₂O)₆]·1.48­(ClO₄)·1.52­(NO₃)·3H₂O (<b>13</b>·3H₂O). Complex <b>1</b> describes a distorted tetrahedral metallic cluster, while complex <b>2</b> can be considered to be a 2-D coordination polymer. Complexes <b>3</b>–<b>13</b> can all be regarded as metallo-cryptand encapsulated lanthanides in which the central lanthanide ion is captivated within a [Co^II₆] trigonal prism. dc and ac magnetic susceptibility studies have been carried out in the 2–300 K range for complexes <b>1</b>, <b>3</b>, <b>5</b>, <b>7</b>, <b>8</b>, <b>10</b>,<b> 12</b>, and <b>13</b>, revealing the possibility of single molecule magnetism behavior for complex <b>10</b>

Heptanuclear Heterometallic [Cu₆Ln] Clusters: Trapping Lanthanides into Copper Cages with Artificial Amino Acids

Employment of the artificial amino acid 2-amino-isobutyric acid, aibH, in CuII and CuII/LnIII chemistry led to the isolation and characterization of 12 new heterometallic heptanuclear [Cu6Ln­(aib)6(OH)3(OAc)3(NO3)3] complexes consisting of trivalent lanthanide centers within a hexanuclear copper trigonal prism (aibH = 2-amino-butyric acid; Ln = Ce (1), Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Ho (9), Er (10), Tm (11), and Yb (12)). Direct curent magnetic susceptibility studies have been carried out in the 5–300 K range for all complexes, revealing the different nature of the magnetic interactions between the 3d–4f metallic pairs: dominant antiferromagnetic interactions for the majority of the pairs and dominant ferromagnetic interactions for when the lanthanide center is GdIII and DyIII. Furthermore, alternating current magnetic susceptibility studies reveal the possibility of single-molecule magnetism behavior for complexes 7 and 8. Finally, complexes 2, 5–8, 10, and 12 were analyzed using positive ion electrospray mass spectrometry (ES-MS), establishing the structural integrity of the heterometallic heptanuclear cage structure in acetonitrile

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^II₄(aib)₃(aibH)₃(NO₃)]­(NO₃)₄·2.8CH₃OH·0.2H₂O (<b>1</b>·2.8CH₃OH·0.2H₂O), {Na₂[Co^II₂(aib)₂(N₃)₄(CH₃OH)₄]}_<i>n</i> (<b>2</b>), [Co^II₆La^III(aib)₆(OH)₃(NO₃)₂(H₂O)₄(CH₃CN)₂]·0.5­[La­(NO₃)₆]·0.75­(ClO₄)·1.75­(NO₃)·3.2CH₃CN·5.9H₂O (<b>3</b>·3.2CH₃CN·5.9H₂O), [Co^II₆Pr^III(aib)₆(OH)₃(NO₃)₃(CH₃CN)₆]·[Pr­(NO₃)₅]·0.41­[Pr­(NO₃)₃(ClO₄)_0.5(H₂O)_1.5]·0.59­[Co­(NO₃)₃(H₂O)]·0.2­(ClO₄)·0.25H₂O (<b>4</b>·0.25H₂O), [Co^II₆Nd^III(aib)₆(OH)₃(NO₃)_2.8(CH₃OH)_4.7(H₂O)_1.5]·2.7­(ClO₄)·0.5­(NO₃)·2.26CH₃OH·0.24H₂O (<b>5</b>·2.26CH₃OH·0.24H₂O), [Co^II₆Sm^III(aib)₆(OH)₃(NO₃)₃(CH₃CN)₆]·[Sm­(NO₃)₅]·0.44­[Sm­(NO₃)₃(ClO₄)_0.5(H₂O)_1.5]·0.56­[Co­(NO₃)₃(H₂O)]·0.22­(ClO₄)·0.3H₂O (<b>6</b>·0.3H₂O), [Co^II₆Eu^III(aib)₆(OH)₃(NO₃)₃(CH₃OH)_4.87(H₂O)_1.13]­(ClO₄)_2.5(NO₃)_0.5·2.43CH₃OH·0.92H₂O (<b>7</b>·2.43CH₃OH·0.92H₂O), [Co^II₆Gd^III(aib)₆(OH)₃(NO₃)_2.9(CH₃OH)_4.9(H₂O)_1.2]·2.6­(ClO₄)·0.5­(NO₃)·2.58CH₃OH·0.47H₂O (<b>8</b>·2.58CH₃OH·0.47H₂O), [Co^II₆Tb^III(aib)₆(OH)₃(NO₃)₃(CH₃CN)₆]·[Tb­(NO₃)₅]·0.034­[Tb­(NO₃)₃(ClO₄)_0.5(H₂O)_0.5]·0.656­[Co­(NO₃)₃(H₂O)]·0.343­(ClO₄)·0.3H₂O (<b>9</b>·0.3H₂O), [Co^II₆Dy^III(aib)₆(OH)₃(NO₃)_2.9(CH₃OH)_4.92(H₂O)_1.18]­(ClO₄)_2.6(NO₃)_0.5·2.5CH₃OH·0.5H₂O (<b>10</b>·2.5CH₃OH·0.5H₂O), [Co^II₆Ho^III(aib)₆(OH)₃(NO₃)₃(CH₃CN)₆]·0.27­[Ho­(NO₃)₃(ClO₄)_0.35(H₂O)_0.15]·0.656­[Co­(NO₃)₃(H₂O)]·0.171­(ClO₄) (<b>11</b>), [Co^II₆Er^III(aib)₆(OH)₄(NO₃)₂(CH₃CN)_2.5(H₂O)_3.5]­(ClO₄)₃·CH₃CN·0.75H₂O (<b>12</b>·CH₃CN·0.75H₂O), and [Co^II₆Tm^III(aib)₆(OH)₃(NO₃)₃(H₂O)₆]·1.48­(ClO₄)·1.52­(NO₃)·3H₂O (<b>13</b>·3H₂O). Complex <b>1</b> describes a distorted tetrahedral metallic cluster, while complex <b>2</b> can be considered to be a 2-D coordination polymer. Complexes <b>3</b>–<b>13</b> can all be regarded as metallo-cryptand encapsulated lanthanides in which the central lanthanide ion is captivated within a [Co^II₆] trigonal prism. dc and ac magnetic susceptibility studies have been carried out in the 2–300 K range for complexes <b>1</b>, <b>3</b>, <b>5</b>, <b>7</b>, <b>8</b>, <b>10</b>,<b> 12</b>, and <b>13</b>, revealing the possibility of single molecule magnetism behavior for complex <b>10</b>

Heptanuclear Heterometallic [Cu₆Ln] Clusters: Trapping Lanthanides into Copper Cages with Artificial Amino Acids

Employment of the artificial amino acid 2-amino-isobutyric acid, aibH, in Cu^II and Cu^II/Ln^III chemistry led to the isolation and characterization of 12 new heterometallic heptanuclear [Cu₆Ln­(aib)₆(OH)₃(OAc)₃(NO₃)₃] complexes consisting of trivalent lanthanide centers within a hexanuclear copper trigonal prism (aibH = 2-amino-butyric acid; Ln = Ce (<b>1</b>), Pr (<b>2</b>), Nd (<b>3</b>), Sm (<b>4</b>), Eu (<b>5</b>), Gd (<b>6</b>), Tb (<b>7</b>), Dy (<b>8</b>), Ho (<b>9</b>), Er (<b>10</b>), Tm (<b>11</b>), and Yb (<b>12</b>)). Direct curent magnetic susceptibility studies have been carried out in the 5–300 K range for all complexes, revealing the different nature of the magnetic interactions between the 3d–4f metallic pairs: dominant antiferromagnetic interactions for the majority of the pairs and dominant ferromagnetic interactions for when the lanthanide center is Gd^III and Dy^III. Furthermore, alternating current magnetic susceptibility studies reveal the possibility of single-molecule magnetism behavior for complexes <b>7</b> and <b>8</b>. Finally, complexes <b>2</b>, <b>5</b>–<b>8</b>, <b>10</b>, and <b>12</b> were analyzed using positive ion electrospray mass spectrometry (ES-MS), establishing the structural integrity of the heterometallic heptanuclear cage structure in acetonitrile