Metallothioneins (MTs) define a superfamily of ubiquitous cysteine-rich low molecular weight proteins or polypeptides that contain polynuclear metalsulfur coordination sites formed by metal ions with d10 configuration. The most prominent characteristics of these biomolecules, which have been discovered as a cadmium and zinc containing protein in horse kidney by Margoshes and Vallee in 1957,1 are their extremely high metal and sulfur contents (up to 10% w/w). Although MTs have been known as long as about half a century, their precise physiological function is still under debate. According to Kägi and Schäffer, they are thought to play roles both in the intracellular fixation of the essential trace elements zinc and copper, in controlling the concentrations of the free ions of these elements, in regulating their flow to their cellular destinations, in neutralizing the harmful influences of exposure to toxic elements such as cadmium and mercury, and in the protection from a variety of stress conditions.2 More recently, it was concluded by Maret and Vallee that the long sought role of MT lies in the control of the cellular zinc distribution as a function of the energy state of the cell and not in the widely held belief that MT primarily scavenges radicals or detoxifies metals.3 As can be learned by these speculations, investigations directed to explore the structure and chemistry of metallothioneins in greater detail are extremely important taking into account that nature makes use of them as multipurpose proteins. Several reviews covering this issue are available in the literature.4 Today, MTs are known to occur in all animal phyla examined so far as well as in certain fungi, plants, and cyanobacteria. Characterized by a low molecular mass of 6.000-7.000 amu, by 20 totally conserved cysteines out of a total of 61 or 62 amino acid residues (according to ca. 30% by number), without aromatic amino acids such as tyrosine or histidine, the apoprotein from rat liver (thionein) is able to bind a total of seven equivalents of divalent metal ions with d10 configuration such as Zn2+ or Cd2+ in two noninteracting domains. After demetalation, these proteins can be loaded with up to six Cu1+ ions in each domain.5 * To whom correspondence should be addressed. (G.H.) Tel +495251-60-2494. Fax +49-5251-60-3423. E-mail biohenkel@ uni-paderborn.de. (B.K.) Tel +49-251-833-3131. Fax +49-251-8338366. E-mail krebs@uni-muenster.de. † Universität Paderborn. ‡ Universität Münster. 801 Chem. Rev. 2004, 104, 801−824

Metallothioneins: zinc, cadmium, mercury, and copper thiolates and selenolates mimicking protein active site features--structural aspects and biological implications.

Ligand-controlled self-assembly of polynuclear lanthanide–oxo/hydroxo complexes: from synthetic serendipity to rational supramolecular design

Two novel heptanuclear lanthanide clusters of the dicubane-like type [Ln7(μ3-OH)8]13+ (Ln = Ho (1), Yb (2)) were obtained via hydrothermal reaction, and as building blocks, they were formally assembled into porous three-dimensional networks through the linkage of 1,4-naphthalenedicarboxylate (1,4-NDA), forming first examples of porous lanthanide polymers with 1,4-NDA, [Ln7(μ3-OH)8(1,4-NDA)6(OH)0.5(Ac)0.5(H2O)7]·4H2O (Ln = Ho, Yb). The coordinating water molecules and lattice water molecules are enclathrated in the cavities.

Synthesis and characterization of two novel lanthanide coordination polymers with an open framework based on an unprecedented [Ln7(μ3-OH)8]13+ cluster

Three new 3d-4f heterometallic coordination polymers, [Ln 2 (H 2 O) 4 M 2 (H 2 O) 2 (QA) 5 ].nH 2 O (H 2 QA = quinolinic acid; Ln = Gd, M = Ni, n = 7 (1); Ln = Gd, M = Co, n = 6.5 (2); Ln = Dy, M = Co, n = 6.5 (3)), have been synthesized through hydrothermal pretreatment and cooling-down crystallization. These compounds possess the isostructural 3D frameworks with 1 D chairlike channels along the c axis, which are occupied by noncoordinating water molecules. Crystal data: for 1, C 3 5 H 4 1 Gd 2 Ni 2 N 5 O 3 3 , orthorhombic, space group Pna2 1 , with a = 28.567(6) A, b = 14.498(3) A, c = 12.250(2) A, and Z= 4; for 2, C 3 5 H 4 0 Gd 2 Co 2 N 5 O 3 2 . 5 , orthorhombic, space group Pna2 1 , with a = 28.843(3) A, b = 14.4325(13) A, c = 12.2275(9) A, and Z = 4; for 3, C 3 5 H 4 0 Dy 2 Co 2 N 5 O 3 2 . 5 , orthorhombic, space group Pna2 1 , with a = 28.8471(14) A, b = 14.4534(10) A, c = 12.2520(7) A, and Z = 4. The magnetic behaviors for the three compounds have been investigated.

Three-dimensional 3d-4f heterometallic coordination polymers: synthesis, structures, and magnetic properties.

Tetranuclear lanthanide−hydroxo complexes of the general formula [Ln4(μ3-OH)4(AA)x(H2O)y]8+ (1, Ln = Sm, AA = Gly, x = 5, y = 11; 2, Ln = Nd, AA = Ala, x = 6, y = 10; 3, Ln = Er, AA = Val, x = 5, y = 10) have been prepared by α-amino acid controlled hydrolysis of lanthanide ions under near physiological pH conditions (pH 6−7). The core component of these compounds is a cationic cluster [Ln4(μ3-OH)4]8+ whose constituent lanthanide ions and triply bridging hydroxo groups occupy the alternate vertexes of a distorted cube. The amino acid ligands coordinate the lanthanide ions via bridging carboxylate groups. Utilizing l-glutamic acid as the supporting ligand, a cationic cluster complex (4) formulated as [Er4(μ3-OH)4(Glu)3(H2O)8]5+ has been obtained. Its extended solid-state structure is composed of the cubane-like [Er4(μ3-OH)4]8+ cluster building units interlinked by the carboxylate groups of the glutamate ligands. All compounds are characterized by using a combination of spectroscopic techniques and microana...

Lanthanide Coordination with α-Amino Acids under Near Physiological pH Conditions: Polymetallic Complexes Containing the Cubane-Like [Ln4(μ3-OH)4]8+ Cluster Core

Chalcogenolates of the smaller lanthanides (Ln) react with elemental chalcogen to give the first examples of cubane clusters containing Ln ions. Both (py)8Yb4Se4(SePh)4 and (py)10Yb6S6(SPh)6 were isolated; the Se compound exhibits the familiar M4E4 structural motif, while the S compound is best described as a double cube. Both structures reveal unusual trends in Yb−chalcogenido bond lengths.

Cubane Clusters Containing Lanthanide Ions: (py)8Yb4Se4(SePh)4 and (py)10Yb6S6(SPh)6

A series of trivalent lanthanide (Ln) benzenechalcogenolate (EPh, E = S, Se) complexes have been prepared and structurally characterized in an attempt to evaluate how metal size, chalcogen, and solvent influence structure and physical properties The compounds [(py)3Ln(SPh)3]2 (Ln = Ho (1) and Tm (2)), [(py)2Sm(SPh)3]4 (3), [(THF)Sm(SPh)3]4n (4), (THF)3Ln(SePh)3 (Ln = Tm (5), Ho (6), Er (7)), [(py)3Sm(SePh)3]2 (8), and [(THF)4Ln3(SePh)9]n (Ln = Pr (9), Nd (10), and Sm (11)) were isolated and characterized by IR, NMR, and UV−visible spectroscopy Compounds 2−4, 7, 8, and 10 have also been characterized by low-temperature single-crystal X-ray diffraction Three trends in structure are clear First, the tendency to form oligomeric structures is found to increase with the size of the lanthanide ion Second, thiolates bridge metal ions to form polynuclear structures more effectively than selenolates Finally, pyridine displaces bridging chalcogenolates to form less extended structures more effectively than THF

Trivalent Lanthanide Chalcogenolates: Ln(SePh)3, Ln2(EPh)6, Ln4(SPh)12, and [Ln(EPh)3]n (E = S, Se). How Metal, Chalcogen, and Solvent Influence Structure

Unexpected synthetic routes to lanthanide chalcogenido clusters: sm8se6(seph)12(thf)8 and sm7s7(seph)6(dme)7+

Chalcogen-Rich Lanthanide Clusters from Lanthanide Halide Starting Materials: A New Approach to the Low-Temperature Synthesis of LnSx Solids from Molecular Precursors

Octametallic (L)8Ln8E6(EPh)12 clusters (L = Lewis base; Ln = lanthanide ion; E = S, Se; EPh = SPh, SePh) can be prepared either by the reduction of Se−C bonds with low-valent Ln or by the reaction of Ln(SePh)3 with elemental E. Because all possible ligand sites (i.e., L, E, EPh) are reactive, the ligands can be varied systematically to further the understanding of structure/property relationships. Chalcogenolate ligands can be selectively varied, as in the reaction of (THF)8Sm8Se6(SePh)12 with PhSSPh to form (THF)8Sm8Se6(SPh)12. Neutral L can be altered without disrupting structure, as in the replacement of THF with pyridine to give (py)8Sm8Se6(SePh)12. Even chalcogenido ligands can be chemically replaced:  the reaction of (THF)8Sm8Se6(SPh)12 with elemental S gives the all-sulfur cluster (THF)8Sm8S6(SPh)12. All compounds were isolated and characterized by IR and UV−visible spectroscopy and by low-temperature single-crystal X-ray diffraction to confirm that the structures contain cubes of Ln(III) ions with...

Deborah Freedman

Papers

Cubane Clusters Containing Lanthanide Ions: (py)8Yb4Se4(SePh)4 and (py)10Yb6S6(SPh)6

Trivalent Lanthanide Chalcogenolates: Ln(SePh)3, Ln2(EPh)6, Ln4(SPh)12, and [Ln(EPh)3]n (E = S, Se). How Metal, Chalcogen, and Solvent Influence Structure

Unexpected synthetic routes to lanthanide chalcogenido clusters: sm8se6(seph)12(thf)8 and sm7s7(seph)6(dme)7+

Chalcogen-Rich Lanthanide Clusters from Lanthanide Halide Starting Materials: A New Approach to the Low-Temperature Synthesis of LnSx Solids from Molecular Precursors

(THF)8Ln8E6(EPh)12 Cluster Reactivity: Systematic Control of Ln, E, EPh, and Neutral Donor Ligands