Milosz Siczek

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.

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 [Cu(6)Ln(aib)(6)(OH)(3)(OAc)(3)(NO(3))(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 Gd(III) and Dy(III). 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.

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: [Ni(4)(aib)(3)(aibH)(3)(NO(3))](NO(3))(4)·3.05MeOH (1·3.05MeOH), [Ni(6)La(aib)(12)](NO(3))(3)·5.5H(2)O (2·5.5H(2)O), [Ni(6)Pr(aib)(12)](NO(3))(3)·5.5H(2)O (3·5.5H(2)O), [Ni(5)(OH)(2)(l-aba)(4)(OAc)(4)]·0.4EtOH·0.3H(2)O 6(4·0.4EtOH·0.3H(2)O), and [Ni(6)La(l-aba)(12)][La(2)(NO(3))(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 P2(1)3, 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.

Polynuclear manganese amino acid complexes

The reaction of MnCl(2).4H(2)O with DL-valine (Val) in MeOH in the presence of Et-saoH(2) (2-hydroxypropiophenone oxime) and NEt(4)OH forms the complex [Mn(III)(3)Mn(IV)(2)O(2)(CH(3)O)(Et-sao)(6)(Val)].Val.1.5H(2)O (1.Val.1.5H(2)O) in very good yields. A similar reaction of MnCl(2).4H(2)O with Glycine (Gly) in MeOH in the presence of saoH(2) (salicylaldoxime) and Ca(OH)(2) yields the complex [Mn(III)(3)O(sao)(3)(Gly)Cl(MeOH)(3)].1.87 MeOH.0.13H(2)O (2.1.87 MeOH.0.13H(2)O). Replacing saoH(2) with Me-saoH(2) (2-hydroxyethanone oxime) and Gly with HPABA (para-aminobenzoic acid) in the presence of CH(3)ONa in MeOH forms the complex [Mn(6)O(2)(PABA)(2)(Me-sao)(6)(MeOH)(4)(H(2)O)(2)].2[Mn(6)O(2)(PABA)(2)(Me-sao)(6)(MeOH)(2)].11 MeOH (3.11 MeOH) in moderate yields. Magnetic studies for 1 and 2 reveal the presence of both ferromagnetic and antiferromagnetic interactions, leading to S = 2 ground states for both complexes. Complexes 1 and 2 represent the first examples of polynuclear manganese complexes with any naturally occurring alpha-amino acid, while 3 is the first structurally characterised example of a manganese para-aminobenzoate complex.

Enneanuclear [Ni6Ln3] Cages: [LnIII3] Triangles Capping [NiII6] 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(II)6Ln(III)3] 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 (1·5.75MeCN·2Et2O·1.5H2O), [Ni6Dy3(OH)6(HL)6(NO3)3]·2MeCN·2.7Et2O·2.4H2O (2·2MeCN·2.7Et2O·2.4H2O), and [Ni6Er3(OH)6(HL)6(NO3)3]·5.75MeCN·2Et2O·1.5H2O (3·5.75MeCN·2Et2O·1.5H2O). The structure of all three clusters describes a [Ln(III)3] triangle capping a [Ni(II)6] trigonal prism. Direct current magnetic susceptibility studies in the 5-300 K range for complexes 1-3 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(II)6Dy(III)3] analogue, establishing its single molecule magnetism behavior with Ueff = 24 K.

A family of polynuclear cobalt complexes upon employment of an indeno-quinoxaline based oxime ligand

The reaction of Co(OAc)2·4H2O with LH (LH = 11H-indeno[1,2-b]quinoxalin-11-one oxime) in MeOH in the presence of NEt3 forms the complex [CoIII2CoIIO(OAc)3L3]·0.5MeOH·0.2H2O (1·0.5MeOH·0.2H2O), while repeating the reaction under solvothermal conditions yielded the heptanuclear cluster [CoII7L9 (OH)2(OAc)2.7(MeO)0.3(H2O)]·4.6MeOH·3.3H2O (2·4.6MeOH·3.3H2O). Changing the starting metal salt to Co(ClO4)2·6H2O and upon the reaction with LH in the presence of NEt3 under high temperature and pressure, we managed to isolate the decanuclear cluster [CoII10L14(OH)3.6(MeO)0.4](ClO4)2·8.5MeOH·5.75H2O (3·8.5MeOH·5.75H2O), while under normal bench conditions and upon employment of pivalates in the reaction mixture complex [CoII4L4(piv)4(MeOH)2]·MeOH·H2O (4·MeOH·H2O) was formed. Furthermore, the reaction of Co(ClO4)2·6H2O with LH and aibH (2-amino-isobutyric acid) in the presence of NEt3 in MeOH gave the mononuclear complex [CoIIIL(aib)2]·3H2O (5·3H2O), while upon increasing the metal–ligand ratio cluster [CoIII2CoIIL4(aib)2(OH)2]·7.9MeOH (6·7.9MeOH) was isolated. Finally, repeating the reaction that yielded the mononuclear complex 5·3H2O under solvothermal conditions, gave the octanuclear cluster [CoII8L10(aib)2(MeO)2](ClO4)2·6.8MeOH·7H2O (7·6.8MeOH·7H2O). Variable temperature dc magnetic susceptibility studies for complexes 2, 3, 4 and 7, reveal that all clusters display dominant antiferromagnetic interactions leading to small or diamagnetic ground-states, S.

The first amino acid manganese cluster: a [(Mn2Mn3III)-Mn-IV] DL-valine cage

The first polymetallic Mn complex containing an amino acid (the pro-ligand DL-valine) is reported.

An indeno-quinoxaline based oxime ligand for the synthesis of polynuclear Ni(II) clusters

The reaction of Ni(OAc)2·4H2O with LH (LH = 11H-indeno[1,2-b]quinoxalin-11-one oxime) in a mixture of solvents comprising MeCN/MeOH (1 : 1) under solvothermal conditions in the presence of NEt3 forms the complex [Ni3(L)5(OAc)(MeOH)]·2.6MeCN·0.7MeOH·0.2H2O (1·2.6MeCN·0.7MeOH·0.2H2O) in moderate yield. Repeating the reaction in MeOH produces the complex [Ni6(L)6(OAc)4(OMe)2]·1.5MeOH·1.3H2O (2·1.5MeOH·1.3H2O) in good yield, while the reaction between Ni(ClO4)2·6H2O and LH in the presence of NEt3 in MeOH under solvothermal conditions yields complex [Ni5(L)6(OMe)2(OH)(H2O)2(MeOH)2](ClO4)·8.8MeOH·1.4H2O (3·8.8MeOH·1.4H2O). Furthermore, the reaction between Ni(ClO4)2·6H2O, LH and 2-amino-isobutyric acid, aibH, in MeCN in the presence of NEt3 forms complex [Ni7(L)7(aib)4(OH)(MeCN)0.5(H2O)0.5](ClO4)2·4MeCN·0.25H2O (4·4MeCN·0.25H2O) under high temperature/pressure, while the same reaction in MeOH yields complex [Ni8(L)8(aib)3(OMe)3](ClO4)2·0.75MeOH·4.2H2O (5·0.75MeOH·4.2H2O). Variable temperature dc magnetic susceptibility studies show that all 1–5 clusters display a small or a diamagnetic ground-state, S.

trans-Dioxidotetra-pyridine-rhenium(V) triiodide.

In the title salt, [ReO2(C5H5N)4]I3, the cation and anion are both located on centres of symmetry. The ReV atom adopts a trans-ReO2N4 octahedral coordination and short intramolecular C—H⋯O contacts occur within the cation. In the crystal, the cations form layers perpendicular to [100] and a weak C—H⋯O interaction links the cations.

A bulky oxime for the synthesis of Mn(III) clusters

The reaction between Mn(OAc)2·4H2O and Br-saoH2 (=5-Br-salicylaldoxime) in EtOH in the presence of NMe4OH led to the formation of the hexanuclear cluster [Mn6O2(Br-sao)6(OAc)2(H2O)2(EtOH)2]·2.8H2O·2.2EtOH (1). Switching from Mn(OAc)2·4H2O to Mn(ClO4)2·6H2O, the same reaction upon addition of pivH (= trimethyl acetic acid) yielded [Mn6O2(Br-sao)6(piv)2(H2O)2(EtOH)2]·6EtOH (2 6EtOH), and finally upon changing pivH to NaO2CPh, we were able to isolate [Mn6Na2O2(Br-sao)6(O2CPh)4(H2O)2(EtOH)4]·6EtOH (3 6EtOH). Clusters 1 and 2 6EtOH describe “typical” [Mn6/oximate] complexes consisting of two {Mn3} oxo-centered triangular units bridged by oximate groups, while in 3 6EtOH these triangular motifs are separated by two sodium cations. An investigation into the magnetic properties of all three clusters revealed the presence of dominant antiferromagnetic interactions, leading to ground states of S = 4 and 2 for 1 and 3, respectively. Finally, cluster 2 6EtOH functions as a single-molecule magnet with Ueff = 27.54 K. Graphical abstract