3d-Metal derivatives of the [Cu(I)(SO3)4]7- ion: structure and magnetism

The Cu(SO(3))(4)(7-) anion, which consists of a tetrahedrally coordinated Cu(I) centre coordinated to four sulfur atoms, is able to act as a multidentate ligand in discrete and infinite supramolecular species. The slow oxidation of an aqueous solution of Na(7)Cu(SO(3))(4) yields a mixed oxidation state, 2D network of composition Na(5){[Cu(II)(H(2)O)][Cu(I)(SO(3))(4)]}·6H(2)O. The addition of Cu(II) and 2,2'-bipyridine to an aqueous Na(7)Cu(SO(3))(4) solution leads to the formation of a pentanuclear complex of composition {[Cu(II)(H(2)O)(bipy)](4)[Cu(I)(SO(3))(4)]}(+); a combination of hydrogen bonding and π-π stacking interactions leads to the generation of infinite parallel channels that are occupied by disordered nitrate anions and water molecules. A pair of Cu(SO(3))(4)(7-) anions each act as a tridentate ligand towards a single Mn(II) centre when Mn(II) ions are combined with an excess of Cu(SO(3))(4)(7-). An anionic pentanuclear complex of composition {[Cu(I)(SO(3))(4)](2)[Fe(III)(H(2)O)](3)(O)} is formed when Fe(II) is added to a Cu(+)/SO(3)(2-) solution. Hydrated ferrous [Fe(H(2)O)(6)(2+)] and sodium ions act as counterions for the complexes and are responsible for the formation of an extensive hydrogen bond network within the crystal. Magnetic susceptibility studies over the temperature range 2-300 K show that weak ferromagnetic coupling occurs within the Cu(II) containing chains of Na(5){[Cu(II)(H(2)O)][Cu(I)(SO(3))(4)]}·6H(2)O, while zero coupling exists in the pentanuclear cluster {[Cu(II)(H(2)O)(bipy)](4)[Cu(I)(SO(3))(4)]}(NO(3))·H(2)O. Weak Mn(II)-O-S-O-Mn(II) antiferromagnetic coupling occurs in Na(H(2)O)(6){[Cu(I)(SO(3))(4)][Mn(II)(H(2)O)(2)](3)}, the latter formed when Mn was in excess during synthesis. The compound, Na(3)(H(2)O)(6)[Fe(II)(H(2)O)(6)](2){[Cu(I)(SO(3))(4)](2)[Fe(III)(H(2)O)](3)(O)}·H(2)O, contained trace magnetic impurities that affected the expected magnetic behaviour.     

Novel polyoxometalate hybrids consisting of copper-lanthanide heterometallic/lanthanide germanotungstate fragments

Three organic-inorganic hybrid copper-lanthanide heterometallic germanotungstates, {[Cu(en)(2)(H(2)O)] [Cu(3)Eu(en)(3)(OH)(3)(H(2)O)(2)](α-GeW(11)O(39))}(2)·11H(2)O (1), {[Cu(en)(2)(H(2)O)][Cu(3)Tb(en)(3)(OH)(3)(H(2)O)(2)](α-GeW(11)O(39))}(2)·11H(2)O (2) and {[Cu(en)(2)(H(2)O)][Cu(3)Dy(en)(3)(OH)(3)(H(2)O)(2)](α-GeW(11)O(39))}(2)·10H(2)O (3) and three polyoxometalate hybrids built by lanthanide-containing germanotungstates and copper-ethylendiamine complexes, Na(2)H(6)[Cu(en)(2)(H(2)O)](8){Cu(en)(2)[La(α-GeW(11)O(39))(2)](2)}·18H(2)O (4), K(4)H(2)[Cu(en)(2)(H(2)O)(2)](5)[Cu(en)(2)(H(2)O)](2)[Cu(en)(2)](2){Cu(en)(2)[Pr(α-GeW(11)O(39))(2)](2)}·16H(2)O (5) and KNa(2)H(7)[enH(2)](3)[Cu(en)(2)(H(2)O)](2)[Cu(en)(2)](2){Cu(en)(2)[Er(α-GeW(11)O(39))(2)](2)}·15H(2)O (6) (en = ethylenediamine) have been hydrothermally synthesized and structurally characterized by elemental analyses, inductively coupled plasma atomic emission spectrometry (ICP-AES) analyses, IR spectra, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS) and single-crystal X-ray diffraction. 1-3 are essentially isomorphous and their main skeletons display the interesting dimeric motif {[Cu(3)Ln(en)(3)(OH)(3)(H(2)O)(2)](α-GeW(11)O(39))}(2)(4-), which is constructed from two {Cu(3)LnO(4)} cubane anchored monovacant [α-GeW(11)O(39)](8-) fragments through two W-O-Ln-O-W linkers. The primary backbones of 4-6 exhibit the tetrameric architecture {Cu(en)(2)[Ln(α-GeW(11)O(39))(2)](2)}(24-) built by two 1?:?2-type [Ln(α-GeW(11)O(39))(2)](13-) moieties and one [Cu(en)(2)](2+) bridge, albeit they are not isostructural. To our knowledge, 1-6 are rare polyoxometalate derivatives consisting of copper-lanthanide heterometallic/lanthanide germanotungstate fragments. 1 exhibits antiferromagnetic coupling interactions within the {Cu(3)EuO(4)} cubane units, while 2 and 3 display dominant ferromagnetic interactions between the Tb(III)/Dy(III) and Cu(II) cations. The room-temperature solid-state photoluminescence properties of 1-3 have been investigated.     

A new organic-inorganic hybrid based on the crescent-shaped polyoxoanion [H6SiNb18O54]8- and copper-organic cations

A new organic-inorganic hybrid, [Cu(en)(2)](3){[Cu(en)(2)][H(6)SiNb(18)O(54)]}·22H(2)O (1, en = ethylenediamine) containing the crescent-shaped polyoxoanion [H(6)SiNb(18)O(54)](8-) and copper-organic cations has been successfully synthesized, and elemental analyses, IR spectra, thermogravimetric analyses and single-crystal X-ray diffraction were investigated.     

Chiral uranium phosphonates constructed from achiral units with three-dimensional frameworks

Two chiral, porous uranium methylenediphosphonates, [C(2)H(10)N(2)]{UO(2)[CH(2)(PO(3))(2)]}·H(2)O (UC1P2N-1) and [N(C(2)H(5))(4)]K{(UO(2))(3)[CH(2)(PO(3))(2)](2)(H(2)O)(2)}·1.5H(2)O (KUC1P2-1), have been synthesized without chiral starting materials. Both compounds display channels ~1 × 1 nm that are large enough for these materials to conduct ion-exchange with coordination complexes such as [Co(en)(3)](3+).     

Two wheel-like polytungstates obtained by incorporation of two {Cu(4)} clusters and two molybdenum centers in the {W(48)} wheel

Two new {P(8)W(48)} wheel-based compounds, Na(12)Li(16){[Cu(H(2)O)](2)[Cu(4)(OH)(4)(H(2)O)(8)](2)P(8)W(48)O(184)}·55H(2)O (1), and K(4)Na(24)Li(10){(MoO(2))(2)(P(8)W(48)O(184))}·61H(2)O (2) have been synthesized by a conventional aqueous solution method, and characterized by UV, IR, TG analysis, XPRD, (31)P NMR, XPS, single-crystal X-ray diffraction analyses, magnetic study and electrochemistry study. In compound 1, a wheel-type {P(8)W(48)} containing two {Cu(4)} clusters and two isolated Cu cations results in a 10-Cu-containing polyoxotungstate, which represents the first {P(8)W(48)}-based compound trapping two transition metal (TM) clusters in its inner cavity. Further, the polyoxoanion was connected by Na(+) and Li(+) cations into a 3D framework. Compound 2 is a 2-Mo-containing {P(8)W(48)}-based polyoxotungstate. Magnetic study indicates that antiferromagnetic interactions exist in compound 1.     

Sensitization of lanthanoid luminescence by organic and inorganic ligands in lanthanoid-organic-polyoxometalates

The reaction of terbium and europium salts with the lacunary polyxometalate (POM) [As(2)W(19)O(67)(H(2)O)](14-) and 2-picolinic acid (picH) affords the ternary lanthanoid-organic-polyoxometalate (Ln-org-POM) complexes [Tb(2)(pic)(H(2)O)(2)(B-β-AsW(8)O(30))(2)(WO(2)(pic))(3)](10-) (1), [Tb(8)(pic)(6)(H(2)O)(22)(B-β-AsW(8)O(30))(4)(WO(2)(pic))(6)](12-) (2), and [Eu(8)(pic)(6)(H(2)O)(22)(B-β-AsW(8)O(30))(4)(WO(2)(pic))(6)](12-) (3). A detailed synthetic investigation has established the conditions required to isolate pure bulk samples of the three complexes as the mixed salts H(0.5)K(8.5)Na[1]·30H(2)O, K(4)Li(4)H(4)[2]·58H(2)O, and Eu(1.66)K(7)[3]·54H(2)O, each of which has been characterized by single crystal X-ray diffraction. Complexes 2 and 3 are isostructural and can be considered to be composed of two molecules of 1 linked through an inversion center with four additional picolinate-chelated lanthanoid centers. When irradiated with a laboratory UV lamp at room temperature, compounds K(4)Li(4)H(4)[2]·58H(2)O and Eu(1.66)K(7)[3]·54H(2)O visibly luminesce green and red, respectively, while compound H(0.5)K(8.5)Na[1]·30H(2)O is not luminescent. A variable temperature photophysical investigation of the three compounds has revealed that both the organic picolinate ligands and the inorganic POM ligands sensitize the lanthanoid(III) luminescence, following excitation with UV light. However, considerably different temperature dependencies are observed for Tb(III) versus Eu(III) through the two distinct sensitization pathways.     

Self-Assembly of Two Chiral Supramolecules with Three-Dimensional Porous Host Frameworks: (Delta){[Fe(II)(phen)(3)][Fe(III)Na(C(2)O(4))(3)]}(n)() and Its Enantiomer

Two chiral supramolecules with enantiomeric three-dimensional porous host frameworks, (Delta){[Fe(II)(phen)(3)][Fe(III)Na(C(2)O(4))(3)]}(n) (1) and (Lambda){[Fe(II)(phen)(3)][Fe(III)Na(C(2)O(4))(3)]}(n) (2) (phen = 1,10-phenanthroline), have been synthesized, and their crystal structures have been determined. The structural analysis shows that compounds 1 and 2 are a pair of enantiomers, both consisting of a three-dimensional porous skeleton formed by (Delta)/(Lambda){[Fe(III)Na(C(2)O(4))(3)](2-)}(n) and guest (Delta)/(Lambda)[Fe(phen)(3)](2+) units. The circular dichroism spectrum measurements confirmed the optical activity and the enantiomeric nature of complexes 1 and 2.     

Synthesis, characterization, and photoresponsive properties of a series of Mo(IV)-Cu(II) complexes

Six Mo(IV)-Cu(II) complexes, [Cu(tpa)](2)[Mo(CN)(8)]·15H(2)O (1, tpa = tris(2-pyridylmethyl)amine), [Cu(tren)](2)[Mo(CN)(8)]·5.25H(2)O (2, tren = tris(2-aminoethyl)amine), [Cu(en)(2)][Cu(0.5)(en)][Cu(0.5)(en)(H(2)O)][Mo(CN)(8)]·4H(2)O (3, en = ethylenediamine), [Cu(bapa)](3)[Mo(CN)(8)](1.5)·12.5H(2)O (4, bapa = bis(3-aminopropyl)amine), [Cu(bapen)](2)[Mo(CN)(8)]·4H(2)O (5, bapen = N,N'-bis(3-aminopropyl)ethylenediamine), and [Cu(pn)(2)][Cu(pn)][Mo(CN)(8)]·3.5H(2)O (6, pn = 1,3-diaminopropane), were synthesized and characterized. Single-crystal X-ray diffraction analyses show that 1-6 have different structures varying from trinuclear clusters (1-2), a one-dimensional belt (3), two-dimensional grids (4-5), to a three-dimensional structure (6). Magnetic and ESR measurements suggest that 1-6 exhibit thermally reversible photoresponsive properties on UV light irradiation through a Mo(IV)-to-Cu(II) charge transfer mechanism. A trinuclear compound [Cu(II)(tpa)](2)[Mo(V)(CN)(8)](ClO(4)) (7) was synthesized as a model of the photoinduced intermediate.     

How does the synthesis temperature impact hybrid organic-inorganic molybdate material design?

We investigate the reactivity of MoO(4)(2-) toward six organoammonium cations (+)(Me(3-x)H(x)N)(CH(2))(2)(NH(y)Me(3-y))(+) (x, y = 1-3) at different synthesis temperatures ranging from 70 to 180 °C. A total of 16 hybrid organic-inorganic materials have been synthesized at an initial pH of 2, via ambient pressure and hydrothermal routes, namely, (H(2)en)[Mo(3)O(10)]·H(2)O (1), (H(2)en)[Mo(3)O(10)] (2), (H(2)en)[Mo(5)O(16)] (3), (H(2)MED)(2)[Mo(8)O(26)]·2H(2)O (4), (H(2)MED)[Mo(5)O(16)] (5), (N,N-H(2)DMED)(2)[Mo(8)O(26)]·2H(2)O (6), (N,N-H(2)DMED)(2)[Mo(8)O(26)]·2H(2)O (7), (N,N'-H(2)DMED)(2)[Mo(8)O(26)] (8), (N,N'-H(2)DMED)[Mo(5)O(16)] (9), (H(2)TriMED)(2)[Mo(8)O(26)]·4H(2)O (10), (H(2)TriMED)(2)[Mo(8)O(26)]·2H(2)O (11), (H(2)TriMED)[Mo(7)O(22)] (12), (H(2)TMED)(2)[Mo(8)O(26)]·2H(2)O (13), (H(2)TMED)(2)[Mo(8)O(26)] (14), (H(2)TMED)(2)[Mo(8)O(26)] (15), and (H(2)TMED)[Mo(7)O(22)] (16). All of these compounds contain different polyoxomolybdate (Mo-POM) blocks, i.e., discrete β-[Mo(8)O(26)](4-) blocks in 6, 10, 13, 14, (1)/(∞)[Mo(3)O(10)](2-), and (1)/(∞)[Mo(8)O(26)](4-) polymeric chains in 1, 2, 4, 7, 8, and 15, respectively, and (2)/(∞)[Mo(5)O(16)](2-) and (2)/(∞)[Mo(7)O(22)](2-) layers in 3, 5, 9, 12, and 16, respectively. The structures of 5, 9, and 14 have been resolved by single-crystal X-ray analyses. The characterization of the different Mo-POM blocks in 1-16 by Fourier transform Raman spectroscopy is reported. The impact of the synthesis temperature on both the composition and topology of the Mo-POM blocks is highlighted.     

Two extended structures constructed from sandwich-type polyoxometalates functionalized by organic amines

Two new compounds constructed from tetra-Ni-substituted sandwich-type polyoxometalates functionalized by organic groups, (NH(4))(2)[Ni(4)(enMe)(8)(H(2)O)(2)Ni(4)(enMe)(2)(PW(9)O(34))(2)].9H(2)O (enMe = 1,2-diaminopropane) (1) and Na(2)[H(6)N(2)(CH(2))(6)](2){Ni(4)[H(4)N(2)(CH(2))(6)](2)(H(2)PW(9)O(34))(2)}.7H(2)O (2), have been successfully synthesized under hydrothermal conditions. Single-crystal X-ray diffraction analysis is carried out on these two compounds (1 and 2), which both crystallize in the triclinic system. Compound 1 represents the first example of a 2D layer structure consisting of the sandwich-type polyoxoanions with six supporting [Ni(enMe)(2)](2+) moities and two organic functionalized groups. Compound 2 exhibits a 1D chain-like structure based on sandwich-type polyoxoanions and sodium cations, which are further connected into a 2D layer structure via hydrogen-bonding interactions between the 1,6-hexanediamine molecules and the sandwich-type [Ni(4)(H(4)N(2)(CH(2))(6))(2)(H(2)PW(9)O(34))(2)](6-) polyoxoanions. A magnetic study of the two compounds indicates that intramolecular ferromagnetic Ni-Ni interactions exist in the tetranuclear metal cluster.     

Two three-dimensional {V16Ge4}-based open frameworks stabilized by diverse types of Co(II)-amine bridges and magnetic properties

Two novel three-dimensional (3D) extended vanadogermanate-based frameworks, [Co(pdn)(2)](3)[Co(2)(pdn)(4)][V(16)Ge(4)O(44)(OH)(2)(H(2)O)]·5H(2)O (1), [Co(2)(en)(3)][Co(en)(2)](2)[Co(en)(2)(H(2)O)][V(16)Ge(4)O(44)(OH)(2)(H(2)O)]·10.5H(2)O (2), (pdn = 1,2-propanediamine, en = ethylenediamine) have been synthesized under hydrothermal conditions via changing the organic amine. X-ray crystal structure analyses reveal that both frameworks are built of [V(16)Ge(4)O(44)(OH)(2)(H(2)O)](10-) anions and different Co-amine cations. They represent the first example of incorporating elemental Co into the extended vanadogermanate frameworks. Compound 1 shows a 3D framework with NaCl topology based on {V(16)Ge(4)} clusters as nodes, while compound 2 exhibits a 3D (4,6)-connected network with a Schl?fli symbol of (4(6)·6(7)·8(2))(2)(4(2)·6(4)), which is found for the first time in polyoxovanadate chemistry. The diverse types of metal-organoamine subunits play critical roles in the formation on the final structures. Furthermore, variable temperature susceptibility measurements on compounds 1 and 2 demonstrate the presence of anticipated rare ferrimagnetic behavior.     

Coordination site-dependent cation binding and multi-responsible redox properties of Janus-head metalloligand, [Mo(V)(1,2-mercaptophenolato)3

The redox-active fac-[Mo(V)(mp)(3)](-) (mp: o-mercaptophenolato) bearing asymmetric O- and S-cation binding sites can bind with several kinds of metal ions such as Na(+), Mn(II), Fe(II), Co(II), Ni(II), and Cu(I). The fac-[Mo(V)(mp)(3)](-) metalloligand coordinates to Na(+) to form the contact ion pair {Na(+)(THF)(3)[fac-Mo(V)(mp)(3)]} (1), while a separated ion pair, n-Bu(4)N[fac-Mo(V)(mp)(3)] (2), is obtained by exchanging Na(+) with n-Bu(4)N(+). In the presence of asymmetric binding-sites, the metalloligand reacts with Mn(II)Cl(2)·4H(2)O, Fe(II)Cl(2)·4H(2)O, Co(II)Cl(2)·6H(2)O, and Ni(II)Cl(2)·6H(2)O to afford UV-vis-NIR spectra, indicating binding of these guest metal cations. Especially, for the cases of the Mn(II) and Co(II) products, trinuclear complexes, {M(H(2)O)(MeOH)[fac-Mo(V)(mp)(3)](2)}·1.5CH(2)Cl(2) (3·1.5CH(2)Cl(2) (M = Mn(II)), 4·1.5CH(2)Cl(2) (M = Co(II))), are successfully isolated and structurally characterized where the M are selectively bound to the hard O-binding sites of the fac-[Mo(V)(mp)(3)](-). On the other hand, a coordination polymer, {Cu(I)(CH(3)CN)[mer-Mo(V)(mp)(3)]}(n) (5), is obtained by the reaction of fac-[Mo(V)(mp)(3)](-) with [Cu(I)(CH(3)CN)(4)]ClO(4). In sharp contrast to the cases of 1, 3·1.5CH(2)Cl(2), and 4·1.5CH(2)Cl(2), the Cu(I) in 5 are selectively bound to the soft S-binding sites, where each Cu(I) is shared by two [Mo(V)(mp)(3)](-) with bidentate or monodentate coordination modes. The second notable feature of 5 is found in the geometric change of the [Mo(V)(mp)(3)](-), where the original fac-form of 1 is isomerized to the mer-[Mo(V)(mp)(3)](-) in 5, which was structurally and spectroscopically characterized for the first time. Such isomerization demonstrates the structural flexibility of the [Mo(V)(mp)(3)](-). Spectroscopic studies strongly indicate that the association/dissociation between the guest metal ions and metalloligand can be modulated by solvent polarity. Furthermore, it was also found that such association/dissociation features are significantly influenced by coexisting anions such as ClO(4)(-) or B(C(6)F(5))(4)(-). This suggests that coordination bonds between the guest metal ions and metalloligand are not too static, but are sufficiently moderate to be responsive to external environments. Moreover, electrochemical data of 1 and 3·1.5CH(2)Cl(2) demonstrated that guest metal ion binding led to enhance electron-accepting properties of the metalloligand. Our results illustrate the use of a redox-active chalcogenolato complex with a simple mononuclear structure as a multifunctional metalloligand that is responsive to chemical and electrochemical stimuli.     

Novel hexagonal {V=O}6-containing sandwich-type cluster accompanied by in situ carbon-carbon bond formation of organic cations

Two novel sandwich-type polyanions containing hexagonal {V=O}(6) group (H(2)tpy)(Hbpe)(3)H[(VO)(6)(SbW(9)O(33))(2)]·2H(2)O (1) and (H(2)tcy)(6)(Hbpp)(6)H(4)[VW(12)O(40)][(VO)(6)(SbW(9)O(33))(2)](3)·30H(2)O (2) (tpy = 4-(2,3,4-tri(pyridin-4-yl)butyl)pyridine, bpe = 1,2-(4-pyridyl)ethene, tcy = 1,2,4,5-tetra(pyridin-4-yl)cyclohexanol, bpp = 1,3-bis-(4-pyridyl)propane), were reported. Both compounds are built upon the complex hydrogen bonding networks of C-H···O and N-H···O occurred among inorganic anions and organic cations. Unusual in situ organic reactions involving C-C coupling are also observed in 1 and 2 regardless of the rigid bpe or flexible bpp. Compound 2 represents a rare case in which nano-sized α-Keggin [VW(12)O(40)](4-) and sandwich-type [(VO)(6)(SbW(9)O(33))(2)](6-) anionic clusters are present in a common crystal framework.     

Structure and magnetism of the tetra-copper(II)-substituted heteropolyanion [Cu(4)K(2)(H(2)O)(8)(alpha-AsW(9)O(33))(2)](8-)

The novel heteropolyanion [Cu(4)K(2)(H(2)O)(8)(alpha-AsW(9)O(33))(2)](8)(-) (1) has been synthesized and characterized by IR spectroscopy, elemental analysis, and magnetic studies. Single-crystal X-ray analysis was carried out on [K(7)Na[Cu(4)K(2)(H(2)O)(6)(alpha-AsW(9)O(33))(2)].5.5H(2)O](n)(K(7)Na-1), which crystallizes in the tetragonal system, space group P42(1)m, with a = 16.705(4) A, b = 16.705(4) A, c = 13.956(5) A, and Z = 2. Interaction of the lacunary [alpha-AsW(9)O(33)](9)(-) with Cu(2+) ions in neutral, aqueous medium leads to the formation of the dimeric polyoxoanion 1 in high yield. Polyanion 1 consists of two alpha-AsW(9)O(33) units joined by a cyclic arrangement of four Cu(2+) and two K(+) ions, resulting in a structure with C(2)(v)() symmetry. All copper ions have one terminal water molecule, resulting in square-pyramidal coordination geometry. Three of the copper ions are adjacent to each other and connected via two micro(3)-oxo bridges. EPR studies on K(7)Na-1 and also on Na(9)[Cu(3)Na(3)(H(2)O)(9)(alpha-AsW(9)O(33))(2)].26H(2)O (Na(9)-2) over 2-300 K yielded g values that are consistent with a square-pyramidal coordination around the copper(II) ions in 1 and 2. No hyperfine structure was observed due to the presence of strong spin exchange, but fine structure was observed for the excited (S(T) = 3/2) state of Na(9)-2 and the ground state (S(T) = 1) of K(7)Na-1. The zero-field (D) parameters have also been determined for these states, constituting a rare case wherein one observes EPR from both the ground and the excited states. Magnetic susceptibility data show that Na(9)-2 has antiferromagnetically coupled Cu(2+) ions, with J = -1.36 +/- 0.01 cm(-)(1), while K(7)Na-1 has both ferromagnetically and antiferromagnetically coupled Cu(2+) ions (J(1) = 2.78 +/- 0.13 cm(-)(1), J(2) = -1.35 +/- 0.02 cm(-)(1), and J(3) = -2.24 +/- 0.06 cm(-)(1)), and the ground-state total spins are S(T) = 1/2 in Na(9)-2 and S(T) = 1 in K(7)Na-1.     

Synthesis and characterization of iron(III)-substituted, dimeric polyoxotungstates, [Fe(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](n-) (n = 6, X = As(III), Sb(III); n = 4, X = Se(IV), Te(IV))

Interaction of the lacunary [alpha-XW(9)O(33)](9-) (X = As(III), Sb(III)) with Fe(3+) ions in acidic, aqueous medium leads to the formation of dimeric polyoxoanions, [Fe(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](6-) (X = As(III), Sb(III)) in high yield. X-ray single-crystal analyses were carried out on Na(6)[Fe(4)(H(2)O)(10)(beta-AsW(9)O(33))(2)] x 32H(2)O, which crystallizes in the monoclinic system, space group C2/m, with a = 20.2493(18) A, b = 15.2678(13) A, c = 16.0689(14) A, beta = 95.766(2) degrees, and Z = 2; Na(6)[Fe(4)(H(2)O)(10)(beta-SbW(9)O(33))(2)] x 32H(2)O is isomorphous with a = 20.1542(18) A, b = 15.2204(13) A, c = 16.1469(14) A, and beta = 95.795(2) degrees. The selenium and tellurium analogues are also reported, [Fe(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](4-) (X = Se(IV), Te(IV)). They are synthesized from sodium tungstate and a source of the heteroatom as precursors. X-ray single-crystal analysis was carried out on Cs(4)[Fe(4)(H(2)O)(10)(beta-SeW(9)O(33))(2)] x 21H(2)O, which crystallizes in the triclinic system, space group P macro 1, with a = 12.6648(10) A, b = 12.8247(10) A, c = 16.1588(13) A, alpha = 75.6540(10) degrees, beta = 87.9550(10) degrees, gamma = 64.3610(10) gamma, and Z = 1. All title polyanions consist of two (beta-XW(9)O(33)) units joined by a central pair and a peripheral pair of Fe(3+) ions leading to a structure with idealized C(2h) symmetry. It was also possible to synthesize the Cr(III) derivatives [Cr(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](6-) (X = As(III), Sb(III)), the tungstoselenates(IV) [M(4)(H(2)O)(10)(beta-SeW(9)O(33))(2)]((16)(-)(4n)-) (M(n+) = Cr(3+), Mn(2+), Co(2+), Ni(2+), Zn(2+), Cd(2+), and Hg(2+)), and the tungstotellurates(IV) [M(4)(H(2)O)(10)(beta-TeW(9)O(33))(2)]((16-4n)-) (M(n+) = Cr(3+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), and Hg(2+)), as determined by FTIR. The electrochemical properties of the iron-containing species were also studied. Cyclic voltammetry and controlled potential coulometry aided in distinguishing between Fe(3+) and W(6+) waves. By variation of pH and scan rate, it was possible to observe the stepwise reduction of the Fe(3+) centers.     

Di- and tetra-nuclear copper(II), nickel(II), and cobalt(II) complexes of four bis-tetradentate triazole-based ligands: synthesis, structure, and magnetic properties

Four bis-tetradentate N(4)-substituted-3,5-{bis[bis-N-(2-pyridinemethyl)]aminomethyl}-4H-1,2,4-triazole ligands, L(Tz1)-L(Tz4), differing only in the triazole N(4) substituent R (where R is amino, pyrrolyl, phenyl, or 4-tertbutylphenyl, respectively) have been synthesized, characterized, and reacted with M(II)(BF(4))(2)·6H(2)O (M(II) = Cu, Ni or Co) and Co(SCN)(2). Experiments using all 16 possible combinations of metal salt and L(TzR) were carried out: 14 pure complexes were obtained, 11 of which are dinuclear, while the other three are tetranuclear. The dinuclear complexes include two copper(II) complexes, [Cu(II)(2)(L(Tz2))(H(2)O)(4)](BF(4))(4) (2), [Cu(II)(2)(L(Tz4))(BF(4))(2)](BF(4))(2) (4); two nickel(II) complexes, [Ni(II)(2)(L(Tz1))(H(2)O)(3)(CH(3)CN)](BF(4))(4)·0.5(CH(3)CN) (5) and [Ni(II)(2)(L(Tz4))(H(2)O)(4)](BF(4))(4)·H(2)O (8); and seven cobalt(II) complexes, [Co(II)(2)(L(Tz1))(μ-BF(4))](BF(4))(3)·H(2)O (9), [Co(II)(2)(L(Tz2))(μ-BF(4))](BF(4))(3)·2H(2)O (10), [Co(II)(2)(L(Tz3))(H(2)O)(2)](BF(4))(4) (11), [Co(II)(2)(L(Tz4))(μ-BF(4))](BF(4))(3)·3H(2)O (12), [Co(II)(2)(L(Tz1))(SCN)(4)]·3H(2)O (13), [Co(II)(2)(L(Tz2))(SCN)(4)]·2H(2)O (14), and [Co(II)(2)(L(Tz3))(SCN)(4)]·H(2)O (15). The tetranuclear complexes are [Cu(II)(4)(L(Tz1))(2)(H(2)O)(2)(BF(4))(2)](BF(4))(6) (1), [Cu(II)(4)(L(Tz3))(2)(H(2)O)(2)(μ-F)(2)](BF(4))(6)·0.5H(2)O (3), and [Ni(II)(4)(L(Tz3))(2)(H(2)O)(4)(μ-F(2))](BF(4))(6)·6.5H(2)O (7). Single crystal X-ray structure determinations revealed different solvent content from that found by microanalysis of the bulk sample after drying under a vacuum and confirmed that 5', 8', 9', 11', 12', and 15' are dinuclear while 1' and 7' are tetranuclear. As expected, magnetic measurements showed that weak antiferromagnetic intracomplex interactions are present in 1, 2, 4, 7, and 8, stabilizing a singlet spin ground state. All seven of the dinuclear cobalt(II) complexes, 9-15, have similar magnetic behavior and remain in the [HS-HS] state between 300 and 1.8 K.     

Sandwich-type germanotungstates: structure and magnetic properties of the dimeric polyoxoanions [M4(H2O)2(GeW9O34)2]12 - (M = Mn2+, Cu2+, Zn2+, Cd2+)

The novel dimeric germanotungstates [M(4)(H(2)O)(2)(GeW(9)O(34))(2)](12)(-) (M = Mn(2+), Cu(2+), Zn(2+), Cd(2+)) have been synthesized and characterized by IR spectroscopy, elemental analysis, magnetic measurements, and (183)W-NMR spectroscopy. X-ray single-crystal analyses were carried out on Na(12)[Mn(4)(H(2)O)(2)(GeW(9)O(34))(2)].38H(2)O (Na(12)()-1), which crystallizes in the monoclinic system, space group P2(1)/n, with a = 13.0419(8) A, b = 17.8422(10) A, c = 21.1626(12) A, beta = 93.3120(10) degrees, and Z = 2; Na(11)Cs(2)[Cu(4)(H(2)O)(2)(GeW(9)O(34))(2)]Cl.31H(2)O (Na(11)()Cs-2) crystallizes in the triclinic system, space group P, with a = 12.2338(17) A, b = 12.3833(17) A, c = 15.449(2) A, alpha = 100.041(2) degrees, beta = 97.034(2) degrees, gamma = 101.153(2) degrees, and Z = 1; Na(12)[Zn(4)(H(2)O)(2)(GeW(9)O(34))(2)].32H(2)O (Na(12)()-3) crystallizes in the triclinic system, space group P, with a = 11.589(3) A, b = 12.811(3) A, c = 17.221(4) A, alpha = 97.828(6) degrees, beta = 106.169(6) degrees, gamma = 112.113(5) degrees, and Z = 1; Na(12)[Cd(4)(H(2)O)(2)(GeW(9)O(34))(2)].32.2H(2)O (Na(12)()-4) crystallizes also in the triclinic system, space group P, with a = 11.6923(17) A, b = 12.8464(18) A, c = 17.616(2) A, alpha = 98.149(3) degrees, beta = 105.677(3) degrees, gamma = 112.233(2) degrees, and Z = 1. The polyanions consist of two lacunary B-alpha-[GeW(9)O(34)](10)(-) Keggin moieties linked via a rhomblike M(4)O(16) (M = Mn, Cu, Zn, Cd) group leading to a sandwich-type structure. (183)W-NMR studies of the diamagnetic Zn and Cd derivatives indicate that the solid-state polyoxoanion structures are preserved in solution. EPR measurements on Na(12)()-1 at frequencies up to 188 GHz and temperatures down to 4 K yield a single, exchange-narrowed peak, at g(iso) = 1.9949, typical of Mn systems, and an upper limit of |D| = 20.0 mT; its magnetization studies still await further theoretical treatment. Detailed EPR studies on Na(11)()Cs-2 over temperatures down to 2 K and variable frequencies yield g( parallel ) = 2.4303 and g( perpendicular ) = 2.0567 and A( parallel ) = 4.4 mT (delocalized over the Cu(4) framework), with |D| = 12.1 mT. Magnetization studies in addition yield the exchange parameters J(1) = -11 and J(2) = -82 cm(-)(1), in agreement with the EPR studies.     

Two dysprosium-incorporated tungstoarsenates: synthesis, structures and magnetic properties

Two dysprosium-containing tungstoarsenates [C(NH(2))(3)](11)[Dy(2)(Hcit)(2)(AsW(10)O(38))]·9H(2)O (1) and K(8-n)H(3-n)[Dy(3-n)K(n)(H(2)O)(3)(CO(3))(A-α-AsW(9)O(34))(A-β-AsW(9)O(34))]·22H(2)O (n = 0 or 1) (2) have been synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, thermogravimetric analyses and infrared spectroscopy. Compound 1 is a citrate-decorated Keggin type di-substituted Ln/POM derivative with the two non-adjacent substituted sites occupied. Compound 2 is composed of two different trivacant Keggin unit isomers [A-α-AsW(9)O(34)](9-) and [A-β-AsW(9)O(34)](9-), linked to each other via one {Dy(3-n)K(n)(H(2)O)(3)(CO(3))}((7 - 2n)+) (n = 0 or 1) unit, where CO(3)(2-) is encapsulated in the triangle plane, resulting in a stable dysprosium carbonate-containing sandwich-type polyoxoanion with D(2h) symmetry. The investigation on both static and dynamic magnetic properties of 1 and 2 show that the magnetic relaxation behavior of 2 appear in a static magnetic field of 5000 Oe, while 1 shows no positive out-of-phase ac susceptibility.     

Photochromic hybrid materials of cucurbituril and polyoxometalates as photocatalysts under visible light

Two isostructural organic-inorganic hybrid solid materials based on cucurbituril derivatives and polyoxometalates, {[K(2)(H(2)O)(2)Na(2)(H(2)O)(2)Na(2)(H(2)O)(6)](P(2)W(18)O(62))(Me(10)Q(5))(2)}·~7H(2)O (1) and {[Rb(2)(H(2)O)(2)Na(2)(H(2)O)Na(2)(H(2)O)(4)](P(2)W(18)O(62))(Me(10)Q(5))(2)}·~8H(2)O (2), which exhibit reversible photochromic properties as well as excellent photocatalytic activities toward the degradation of methyl orange (MO) and rhodamine-B (RB) under visible light irradiation, are reported.     

A copper(ii)-ethylenediamine modified polyoxoniobate with photocatalytic H(2) evolution activity under visible light irradiation

A new dimer polyoxoniobate [Cu(en)(2)](11)K(4)Na(2)[KNb(24)O(72)H(9)](2)·120H(2)O (1) has been synthesized and systematically characterized. Visible light photocatalytic H(2) evolution activity was researched with 1 as the visible-light photosensitizer and catalyst, cobaloximes [Co(III)(dmgH)(2)pyCl] as the co-catalysts, and triethylamine (TEA) as the sacrificial electron donor.