Pentanuclear Thorium(IV) Coordination Cluster from the Use of Di(2-pyridyl) Ketone.

The Th(NO3)4·5H2O/di(2-pyridyl) ketone [(py)2CO] reaction system gives a pentanuclear cluster containing the doubly deprotonated form of the gem-diol derivative of the ligand. The cluster consists of a tetrahedral arrangement of four ThIV ions centered on the fifth ion, which is the first characterized ThIV5 complex. The analysis of its structure reveals that this is a Kuratowski-type coordination compound.

Oligonuclear Actinoid Complexes with Schiff Bases as Ligands-Older Achievements and Recent Progress.

Even 155 years after their first synthesis, Schiff bases continue to surprise inorganic chemists. Schiff-base ligands have played a major role in the development of modern coordination chemistry because of their relevance to a number of interdisciplinary research fields. The chemistry, properties and applications of transition metal and lanthanoid complexes with Schiff-base ligands are now quite mature. On the contrary, the coordination chemistry of Schiff bases with actinoid (5f-metal) ions is an emerging area, and impressive research discoveries have appeared in the last 10 years or so. The chemistry of actinoid ions continues to attract the intense interest of many inorganic groups around the world. Important scientific challenges are the understanding the basic chemistry associated with handling and recycling of nuclear materials; investigating the redox properties of these elements and the formation of complexes with unusual metal oxidation states; discovering materials for the recovery of trans-{UVIO2}2+ from the oceans; elucidating and manipulating actinoid-element multiple bonds; discovering methods to carry out multi-electron reactions; and improving the 5f-metal ions' potential for activation of small molecules. The study of 5f-metal complexes with Schiff-base ligands is a currently "hot" topic for a variety of reasons, including issues of synthetic inorganic chemistry, metalosupramolecular chemistry, homogeneous catalysis, separation strategies for nuclear fuel processing and nuclear waste management, bioinorganic and environmental chemistry, materials chemistry and theoretical chemistry. This almost-comprehensive review, covers aspects of synthetic chemistry, reactivity and the properties of dinuclear and oligonuclear actinoid complexes based on Schiff-base ligands. Our work focuses on the significant advances that have occurred since 2000, with special attention on recent developments. The review is divided into eight sections (chapters). After an introductory section describing the organization of the scientific information, Sections 2 and 3 deal with general information about Schiff bases and their coordination chemistry, and the chemistry of actinoids, respectively. Section 4 highlights the relevance of Schiff bases to actinoid chemistry. Sections 5-7 are the "main menu" of the scientific meal of this review. The discussion is arranged according the actinoid (only for Np, Th and U are Schiff-base complexes known). Sections 5 and 7 are further arranged into parts according to the oxidation states of Np and U, respectively, because the coordination chemistry of these metals is very much dependent on their oxidation state. In Section 8, some concluding comments are presented and a brief prognosis for the future is attempted.

A Ferromagnetically Coupled, Bell-Shaped [Ni4Gd5] Cage.

Reaction between NiCl2·6H2O, 2-hydroxy-4-methyl-6-phenyl-pyridine-3-amidoxime (H2L), benzoic acid, and M(NO3)3·6H2O (M = Gd, Y) in MeCN under basic conditions yields the complexes [NiII4GdIII5(PhCOO)10(HL)4(HLzw)4(OH)2(NO3)2]Cl·13.6MeCN·H2O (1·13.6MeCN·H2O) and [NiII4YIII5(PhCOO)10(HL)4(HLzw)4(OH)2(NO3)1.5(H2O)0.5]0.5Cl(NO3)·3H2O (2·3H2O). Both clusters display similar structures, consisting of a bell-shaped {NiII4MIII5} unit, in which a linear "zigzag" {Ni4} subunit bisects the central {MIII5} "ring". Direct (dc) and alternating current (ac) magnetic susceptibility measurements carried out in the 2-300 K temperature range for complexes 1 and 2 revealed ferromagnetic intermolecular interactions, while heat-capacity measurements for the Gd analogue suggest that complex 1 lowers its temperature from T = 9.6 K down to 2.3 K by adiabatically demagnetizing from Bi = 7 T to Bf = 0.

Enneanuclear [Ni6Ln3] Cages: [Ln(III)3] Triangles Capping [Ni(II)6] Trigonal Prisms Including a [Ni6Dy3] Single-Molecule Magnet.

The use of (2-(ß-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 strongly blue-emitting heptametallic [Dy(III)7] centered-octahedral single-molecule magnet.

The employment of 2-(ß-naphthalideneamino)-2-(hydroxymethyl)-1-propanol and 2-aminoisobutyric acid in dysprosium chemistry has led to the isolation of a novel heptanuclear [Dy(III)(7)] cluster displaying single-molecule-magnetism behavior and blue-emitting properties.

Employment of a new tripodal ligand for the synthesis of cobalt(II/III), nickel(II), and copper(II) clusters: magnetic, optical, and thermal properties.

The employment of 2-(ß-naphthalideneamino)-2-(hydroxymethyl)-1-propanol (LH(3)) in cobalt, nickel, and copper chemistry has led to the isolation of five new metallic complexes with interesting magnetic properties. More specifically, the reaction of Co(OAc)(2)·4H(2)O with LH(3) in MeOH in the presence of NEt(3) under solvothermal conditions forms the complex [Co(III)(2)Co(II)(3)(L)(2)(LH)(2)(L')(OAc)]·8.5MeOH (1·8.5MeOH; L' = monoanion of 2-hydroxy-1-naphthaldehyde), while in nickel chemistry, a similar reaction of Ni(OAc)(2)·6H(2)O with LH(3) in MeCN in the presence of NEt(3) under high pressure/temperature forms the complex [Ni(II)(LH(2))(2)]·2MeCN (2·2MeCN). Repeating the same reaction in MeOH and switching from Ni(OAc)(2)·4H(2)O to NiSO(4)·4H(2)O produces the complex [Ni(II)(4)(HL)(3)(OMe)(MeOH)(3)](SO(4))(0.5)·2MeOH (3·2MeOH) under solvothermal conditions. Furthermore, in copper chemistry, the reaction of Cu(2)(OAc)(4)·2H(2)O with LH(3) in the presence of NEt(3) in MeOH under solvothermal conditions affords the complex [Cu(II)(4)(LH)(4)] (4), while the same reaction under ambient temperature and pressure conditions forms [Cu(II)(4)(LH)(4)] ·3.5MeOH·2.25H(2)O (5·3.5MeOH·2.25H(2)O). Complex 1 is a mixed-valent [Co(III)(2)Co(II)(3)] complex, consisting of three edge-sharing [Co(3)] triangles. Complex 2 is a nickel(II) monomer in which the central metal is found in an octahedral geometry, while complex 3 describes a [Ni(II)(4)] cubane. Complexes 4 and 5 may be considered as structural isomers because they possess the same formulas but different topologies: 4 describes a highly distorted [Cu(II)(4)(OR)(4)](4+) eight-membered ring, while 5 consists of a distorted [Cu(II)(4)(µ(3)-OR)(4)](4+) cubane. In addition, 5 can be converted to 4 in excellent yield under solvothermal conditions. Direct-current magnetic susceptibility studies have been carried out in the 5-300 K range for complexes 1 and 3-5, revealing the possibility of a high-spin ground state for 1, an S = 4 ground state for 2, and diamagnetic ground states for 4 and 5.

Two different coordination modes of the Schiff base derived from ortho-vanillin and 2-(2-aminomethyl)pyridine in a mononuclear uranyl complex.

This work describes the reaction of the potentially tetradentate Schiff-base ligand N-(2-pyridylmethy)-3-methoxysalicylaldimine (HL) with UO2(O2CMe)2·2H2O and UO2(NO3)2· 6H2O in MeOH in the absence or presence of an external base, respectively. The product from these reactions is the mononuclear complex [UO2(L)2] (1). Its structure has been determined by single-crystal, X-ray crystallography. The anionic ligand adopts two different coordination modes (1.1011, 1.1010; Harris notation) in the complex. The new compound was fully characterized by solid-state (IR, Raman and Photoluminescence spectroscopies) and solution (UV-Vis and 1H NMR spectra, conductivity measurements) techniques.

Heterometallic lanthanide-centred [NiLnIII] rings.

A [NiII6DyIII] heptanuclear complex featuring a rare six-membered {NiII6} metal ring surrounding the central Dy(iii) ion is reported. Magnetic studies reveal single-molecule magnet behaviour for the complex under zero external dc field, while replacing the DyIII ion with [capital Upsilon]III or GdIII ions allows for a comprehensive understanding of the magnetic behaviour.

Constructing CrIII-centered heterometallic complexes: [NiCrIII] and [CoCrIII] wheels.

The solvothermal reaction between Cr(acac)3, MCl2·6H2O (M = Ni, Co) and 2-hydroxy-4-methyl-6-phenyl-pyridine-3-amidoxime (H2L), under basic conditions, led to the synthesis of the heterometallic heptanuclear clusters [MCr(HLzw)6(HL)6]·3Cl (M = Ni, 1; Co, 2), with the nickel analogue displaying an S = 9/2 spin ground-state.

Solvothermal synthesis of enneanuclear [Cu7(II)Ln2(III)] clusters.

Employment of H3L (= 2-(ß-naphthalideneamino)-2-hydroxymethyl-1-propanol) in mixed-metal copper-lanthanide cluster chemistry has led to the isolation of four new enneanuclear heteronuclear isostructural [Cu7(II)Ln2(III)] complexes. More specifically, the solvothermal reaction of Cu2(OAc)4·2H2O with H3L and the corresponding lanthanide nitrate salt in MeCN in the presence of a base, NEt3, yielded three complexes with the general formula [Cu7(II)Ln2(III)(L)4(HL)2(OAc)4]·2MeCN (Ln: Gd, 1·2MeCN; Tb, 2·2MeCN; Dy, 3·2MeCN), while in addition the Y(III) analogue, [Cu7(II)Y2(III)(L)4(HL)2(OAc)4]·2MeCN (4·2MeCN), was also synthesized in the same manner. The structure of the cluster describes two corner-sharing [Cu3Ln] cubane metallic units, each one further connected to one Cu(II) ion. Dc magnetic susceptibility studies in the 5-300 K range for complexes 1-4 reveal the presence of both ferromagnetic and antiferromagnetic exchange interactions within the metallic clusters.

Dodecanuclear [Mn6(III)Ln6(III)] species: synthesis, structures and characterization of magnetic relaxation phenomena.

The use of H3L (= 2-(ß-naphthalideneamino)-2-hydroxymethyl-1-propanol) in mixed-metal manganese-lanthanide carboxylate cluster chemistry has led to the isolation of two new dodecametallic heteronuclear isostructural [Mn6(III)Ln6(III)] complexes (Ln = Gd, Dy), with the Dy analogue displaying temperature and frequency dependent out-of-phase signals suggesting possible single molecule magnetism behaviour.

A family of [Mn(III)6Ln(III)2] rod-like clusters.

Employment of H3L (= 2-(ß-naphthalideneamino)-2-hydroxymethyl-1-propanol) in mixed-metal manganese-lanthanide cluster chemistry has led to the isolation of five new octametallic heteronuclear isostructural [Mn(III)6Ln(III)2] complexes. More specifically, the reaction of Mn(ClO4)2·6H2O with H3L and the corresponding lanthanide nitrate in MeCN in the presence of a base, NEt3, yielded four complexes with the general formula [Mn(III)6Ln(III)2O2(OH)2(H2O)2(HL)6(NO3)6]·6MeCN·0.5H2O (Ln: Gd, 1·6MeCN·0.5H2O; Tb, 2·6MeCN·0.5H2O; Dy, 3·6MeCN·0.5H2O; Er, 4·6MeCN·0.5H2O). Furthermore, the Y(III) analogue, [Mn(III)6Y(III)2O2(OH)2(H2O)2(HL)6(NO3)6]·6MeCN·0.5H2O (5·6MeCN·0.5H2O), was also synthesized in the same manner. All five clusters describe a central rod-like topology consisting of four face-sharing defective cubane metallic units, forming a planar hexametallic [Mn(III)4Ln(III)2] core, which is further capped by two Mn(III) ions. Dc magnetic susceptibility studies in the 5-300 K range for complexes 1-5 reveal the presence of dominant antiferromagnetic exchange interactions within the metallic clusters, while ac magnetic susceptibility measurements show temperature and frequency dependent out-of-phase signals for the Dy(III) analogue (3·6MeCN·0.5H2O), suggesting potential single molecule magnetism character. Furthermore, the Y(III) analogue yielded a diamagnetic ground-state for the [Mn(III)6] core, thus proving that the SMM character displayed by 3·6MeCN·0.5H2O is due to the presence of the Dy(III) centres.