Oxygen/sulfur substitution reactions of tetraoxometalates effected by electrophilic carbon and silicon reagents

Reactions of [MO(4)](2)(-) (M = Mo, W) with certain carbon and silicon electrophiles were investigated in acetonitrile in order to produce species of potential utility in the synthesis of analogues of the sites in the xanthine oxidoreductase enzyme family. Silylation of [MoO(4)](2)(-) affords [MoO(3)(OSiPh(3))](1)(-), which with Ph(3)SiSH is converted to [MoO(2)S(OSiPh(3))](1)(-). Reaction with (Ph(3)C)(PF(6))/HS(-) yields the tetrahedral monosulfido species [MO(3)S](2)(-), previously obtained only from the aqueous system [MO(4)](2)(-)/H(2)S. Dithiolene chelate rings are readily introduced upon reaction with 1,2-C(6)H(4)(SSiMe(3))(2), leading to the square pyramidal trioxo complexes [MO(3)(bdt)](2)(-), a previously unknown dithiolene molecular type. Further ring insertion occurs upon reaction of [WO(3)(bdt)](2)(-) with 1,2-C(6)H(4)(SSiMe(3))(2), giving [WO(2)(bdt)(2)](2)(-). Related reactions occur with [ReO(4)](1)(-). Treatment with 1 equiv of (Me(3)Si)(2)S produces [ReO(3)S](1)(-); with 3 equiv of 1,2-C(6)H(4)(SSiMe(3))(2), [ReO(bdt)(2)](1)(-) is obtained with concomitant Re(VII) --> Re(V) reduction. X-ray structures are reported for [MO(3)S](z)(-) (M = Mo, W, z = 2; M = Re, z = 1), [MO(3)(bdt)](2)(-), and [WO(2)(OSiPh(3))(bdt)](1)(-), a silylation product of [WO(3)(bdt)](2)(-). [MoO(3)(bdt)](2)(-) is related to the site of inactive sulfite oxidase, and [WO(2)(OSiPh(3))(bdt)](1)(-) should closely approximate the metric features of the [(dithiolene)MoO(2)(OH)] site in inactive aldehyde/xanthine oxidoreductase. This work provides convenient syntheses of known and new derivatives of tetraoxometalates, among which is entry to a unique class of oxo-monodithiolene complexes.     

New luminescent solids in the Ln-W(Mo)-Te-O-(Cl) systems

Solid-state reactions of lanthanide(III) oxide (and/or lanthanide(III) oxychloride), MoO3 (or WO3), and TeO2 at high temperature lead to eight new luminescent compounds with four different types of structures, namely, Ln2(MoO4)(Te4O10) (Ln = Pr, Nd), La2(WO4)(Te3O7)2, Nd2W2Te2O13, and Ln5(MO4)(Te5O13)(TeO3)2Cl3 (Ln = Pr, Nd; M = Mo, W). The structures of Ln2(MoO4)(Te4O10) (Ln = Pr, Nd) feature a 3D network in which the MoO4 tetrahedra serve as bridges between two lanthanide(III) tellurite layers. La2(WO4)(Te3O7)2 features a triple-layer structure built of a [La2WO4]4+ layer sandwiched between two Te3O72- anionic layers. The structure of Nd2W2Te2O13 is a 3D network in which the W2O108- dimers were inserted in the large tunnels of the neodymium(III) tellurites. The structures of Ln5(MO4)(Te5O13)(TeO3)2Cl3 (Ln = Pr, Nd; M = Mo, W) feature a 3D network structure built of lanthanide(III) ions interconnected by bridging TeO32-, Te5O136-, and Cl- anions with the MO4 (M = Mo, W) tetrahedra capping on both sides of the Ln4 (Ln = Pr, Nd) clusters and the isolated Cl- anions occupying the large apertures of the structure. Luminescent studies indicate that Pr2(MoO4)(Te4O10) and Pr5(MO4)(Te5O13)(TeO3)2Cl3 (M = Mo, W) are able to emit blue, green, and red light, whereas Nd2(MoO4)(Te4O10), Nd2W2Te2O13, and Nd5(MO4)(Te5O13)(TeO3)2Cl3 (M = Mo, W) exhibit strong emission bands in the near-IR region.     

Supramolecular cations of the m-fluoroanilinium(dibenzo[18]crown-6) in ferromagnetic salt

A supramolecular cation of (m-FAni(+))(DB[18]crown-6), where m-FAni(+) and DB[18]crown-6 denote m-fluoroanilinium(+) and dibenzo[18]crown-6, respectively, which is the polar unit rotating in the ferroelectric crystal of (m-FAni(+))(DB[18]crown-6)[Ni(dmit)(2)](-), was introduced into a ferromagnetic [MnCr(oxalate)(3)](-) salt as the counter cation. The crystal structure of (m-FAni(+))(DB[18]crown-6)[MnCr(oxalate)(3)](-)(CH(3)OH)(CH(3)CN) (1) is constructed from alternating layers of a two-dimensional honeycomb layer of [MnCr(oxalate)(3)](-) and (m-FAni(+))(DB[18]crown-6) supramolecular cations. The anionic layer is composed of Mn(II) and Cr(III) ions with S = 5/2 and S = 3/2 spins, respectively, bridged by the oxalate anions, which show ferromagnetic ordering at 5.5 K. The supramolecular structure is formed through the formation of hydrogen bonds between the ammonium hydrogen atoms of the m-FAni(+) cations and the oxygen atoms of the DB[18]crown-6 cavity. No orientational disorder of the fluorine atoms was observed in our X-ray structural analysis, suggesting that a two-fold flip-flop motion of the m-FAni(+) cations does not occur in the salt. The rotational freedom of the m-FAni(+) cations in the salt is restricted by the steric hindrance from neighbouring DB[18]crown-6 molecules. A design strategy for the rotation in a salt is discussed, based on the volume that the supramolecular cations occupy in the unit cell.     

One-pot redox syntheses of heteronanostructures of Ag nanoparticles on MoO3 nanofibers

A new one-pot redox route has been developed for simultaneous syntheses of Ag nanoparticles on MoO(3) nanofibers. Four different synthetic reactions that have been integrated into the one-pot synthesis include the oxidation of [Na(H(2)O)(2)](0.25)MoO(3) bronze, the reduction of silver ions, and the in situ simultaneous growth of the self-organized Ag nanoparticles and the MoO(3) nanofibers. This new strategy can be generally applicable to grafting various metal nanoparticles on nanofibers for new catalysis-related applications.     

Two enantiomers of [Cu(3)(mnt)(3)](3-) as ligands to Cu(i) or Ag(i) in building [Cu(6)M(2)(mnt)(6)](4-) complexes (M = Cu or Ag) with the reversal of the reaction by X(-) (X = Cl, Br)

Two enantiomers of [Bu(4)N](3)[Cu(3)(mnt)(3)] () formed by Na(2)(mnt) (mnt = maleonitriledithiolate, [S(2)C(2)(CN)(2)](2-)) and CuCl in a 1 : 1 molar ratio react further with MCl (M = Cu or Ag) involving both the enantiomers of to produce the larger complex, [Bu(4)N](4)[Cu(6)M(2)(mnt)(6)] (M = Cu (2), Ag (3)) from which the capped Cu(+) or Ag(+) ion can readily be removed by Bu(4)NX (X = Cl, Br), reverting or back to . Such reversal does not work with non-coordinating anions like BF(4)(-), ClO(4)(-) and PF(6)(-).     

Anion dependence of Ag(I) reactions with 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz): isolation of the molecular propeller compound [Ag2(bptz)3][AsF6]2

The new compound [Ag(2)(bptz)(3)][AsF(6)](2), prepared from the reaction of bptz with Ag[AsF(6)] in CH(3)CN, is stable in solution as well as the solid-state and exhibits an unprecedented propeller arrangement of three bptz ligands spanning two Ag(i) ions with [AsF(6)](-) anions located in the folds of the cation.     

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.     

CCl3(+) and CBr3(+) salts with the [Al(OR(F))4]- and [((F)RO)3Al-F-Al(OR(F))3]- anions (R(F) = C(CF3)3)

The CX3(+) salts [CCl(3)](+)[Al(OR(F))(4)](-)1, [CCl(3)](+)[(R(F)O)(3)Al-F-Al(OR(F))(3)](-)2, [CBr(3)](+)[Al(OR(F))(4)](-)3, [CBr(3)](+)[(R(F)O)(3)Al-F-Al(OR(F))(3)](-)4 (R(F) = C(CF(3))(3)) were prepared in 56 to 85% yield from CX(4) (X = Cl, Br) and the corresponding silver salts (weight balance, NMR, IR, X-ray structure of 1). The most convenient solvent for the preparation of 1 and 2 is SO(2)ClF but for 3 and 4 it is SO(2). The reactions are complete after about three days stirring at -30 to -40 °C. The salts are stable for weeks in solution at -40 °C and stable for a few hours at RT in the solid state. In SO(2)ClF (1, 2) or SO(2) (3, 4) solution they decompose slowly at -20 °C and within several hours at RT; in general the CBr3(+) salts are more stable than the CCl3(+) homologues. The decomposition products were assigned as CCl(3)F and primarily CBr(2)F(2) (which likely forms as a Lewis acid induced disproportionation product of the initial CBr(3)F). The C-X vibrations of the salts were found in the expected range and the assignments were made based on experimental and calculated data. The IR spectrum of a CBr3(+) salt is for the first time reported here.     

New structural features of unsupported chains of metal ions in luminescent [(NH3)4Pt][Au(CN)2]2 x 1.5(H2O) and related salts

Luminescent [(NH(3))(4)Pt][Au(CN)(2)](2).1.5(H(2)O), which forms from aqueous solutions of [(NH(3))(4)Pt]Cl(2) and K[Au(CN)(2)], crystallizes with extended chains of the two ions with multiple close Pt...Au (3.2804(4) and 3.2794(4) A) and Au...Au (3.2902(5), 3.3312(5), and 3.1902(4) A) contacts. Nonluminescent [(NH(3))(4)Pt][Ag(CN)(2)](2).1.4(H(2)O) is isostructural with [(NH(3))(4)Pt][Au(CN)(2)](2).1.5(H(2)O). Treatment of [(NH(3))(6)Ni]Cl(2) with K[Au(CN)(2)] forms [(NH(3))(2)Ni][Au(CN)(2)](2) in which the [Au(CN)(2)](-) ions function as nitrile ligands toward nickel, which assumes a six-coordinate structure with trans NH(3) ligands. The [Au(CN)(2)](-) ions self-associate into linear columns with close Au...Au contacts of 3.0830(5) A, and pairs of gold ions in these chains make additional but longer (3.4246(5) A) contacts with other gold ions.     

Metal-metal interactions in platinum(II)/gold(I) or platinum(II)/silver(I) salts containing planar cations and linear anions

The salts [Pt{C(NHMe)(2)}(4)][Au(CN)(2)](2), [Pt{C(NHMe)(2)}(4)][Ag(2)(CN)(3)][Ag(CN)(2)], [Pt(en)(2)][Au(CN)(2)](2), [Pt(en)(2)][Ag(CN)(2)](2), and [Pt(bipy)(2)][Au(CN)(2)](2) have been prepared by mixing solutions of salts containing the appropriate cation with solutions of K[Au(CN)(2)] or K[Ag(CN)(2)]. Because the platinum atom in the cation is sterically protected, the structures of [Pt{C(NHMe)(2)}(4)][Au(CN)(2)](2) and [Pt{C(NHMe)(2)}(4)][Ag(2)(CN)(3)][Ag(CN)(2)] reveal no close metal-metal interactions. Colorless crystals of [Pt(en)(2)][Au(CN)(2)](2) and [Pt(en)(2)][Ag(CN)(2)](2) are isostructural and involve extended chains of alternating cations and anions that run parallel to the crystallographic a axis, along with isolated anions. In the chains, the metal-metal separations are relatively short: Pt...Au, 3.1799(3) Angstroms; Pt...Ag, 3.1949(2) Angstroms. In [Pt(bipy)(2)][Au(CN)(2)](2), each cation has axial interactions with the anions through close Pt...Au contacts [3.1735(6) Angstroms]. In addition, the anions are weakly linked through Au...Au contacts of 3.5978(9) Angstroms. Unlike the previously reported Pt/Au complex [Pt(NH(3))(4)][Au(CN)(2)](2).1.5H(2)O, which is luminescent, none of the salts reported here luminesce.     

Univalent gallium and indium phosphane complexes: from pyramidal M(PPh3)3(+) to carbene-analogous bent M(PtBu3)2(+) (M=Ga, In) complexes

In a new oxidative route, Ag(+)[Al(OR(F))(4)](-) (R(F)=C(CF(3))(3)) and metallic indium were sonicated in aromatic solvents, such as fluorobenzene (PhF), to give a precipitate of silver metal and highly soluble [In(PhF)(n)](+) salts (n=2, 3) with the weakly coordinating [Al(OR(F))(4)](-) anion in quantitative yield. The In(+) salt and the known analogous Ga(+)[Al(OR(F))(4)](-) were used to synthesize a series of homoleptic PR(3) phosphane complexes [M(PR(3))(n)](+), that is, the weakly PPh(3)-bridged [(Ph(3)P)(3)In-(PPh(3))-In(PPh(3))(3)](2+) that essentially contains two independent [In(PPh(3))(3)](+) cations or, with increasing bulk of the phosphane, the carbene-analogous [M(PtBu(3))(2)](+) (M=Ga, In) cations. The M(I)-P distances are 27 to 29 pm longer for indium, and thus considerably longer than the difference between their tabulated radii (18 pm). The structure, formation, and frontier orbitals of these complexes were investigated by calculations at the BP86/SV(P), B3LYP/def2-TZVPP, MP2/def2-TZVPP, and SCS-MP2/def2-TZVPP levels.     

Ca(2+)/vacancies and O2-/F- ordering in new oxyfluoride pyrochlores Li(2x)Ca1.5-x square 0.5-xM2O6F (M = Nb,Ta) for 0 < or = x < or = 0.5

New oxyfluorides Li(2x)Ca(1.5-x) square (0.5-x)M2O6F (M = Nb, Ta), belonging to the cubic pyrochlore structural type (Z = 8, a approximately 10.5 angstroms), were synthesized by solid state reaction for 0 < or = x < or = 0.5. XRD data allowed us to determine their structures from single crystals for the two alpha and beta-Ca(1.5) square (0.5)Nb2O6F forms and from powder samples for the others. This characterisation was completed by TEM and solid state 19F NMR experiments. For the Ca(1.5) square (0.5)M2O6F (x = 0) pyrochlore phases, the presence of a double ordering phenomenon is demonstrated, involving on one hand the Ca(2+) ions and the vacancies and on the other hand the oxide and the fluoride anions which are strictly located in the 8b sites of the Fd3m aristotype space group. The Ca(2+) ions/vacancies ordering leads to a reversible phase transition, a (P4(3)32) <--> beta (Fd3m). The 19F NMR study strongly suggests that, in the beta-phases, the fluoride ions are only on average at the centre of the Ca3 square tetrahedron. It shows that slightly different Ca-F distances occuring in alpha-Ca(1.5) square (0.5)Nb2O6F may be related to a more difficult thermal ionic and vacancies diffusion process than in the tantalate compound. This may explain the hysteresis phenomenon presented by the phase transition. A solid solution Li(2x)Ca(1.5-x) square (0.5-x) Ta2O6F (0 < or = x < or = 0.5) was prepared and the order-disorder phase transition observed for Ca(1.5) square (0.5)M2MO6F compounds disappears for all the other compositions where less or no more vacancies exist in the 16d sites. In the LiCaM2O6F compounds, the 19F NMR study allows us to determine the Ca(2+) and Li+ ions distributions around the fluoride ions and shows that the [FLi2Ca2] environment is clearly favoured.     

Structural phase transition of magnetic [Ni(dmit)2]- salts induced by supramolecular cation structures of (M+)([12]crown-4)2

Sandwich-type supramolecular cation structures of (M(+))([12]crown-4)(2) complexes (M(+) = Li(+), Na(+), K(+), and Rb(+)) were introduced as countercations to the [Ni(dmit)(2)](-) anion, which bears an S = (1)/(2) spin, to form novel magnetic crystals (dmit(2-) = 2-thione-1,3-dithiole-4,5-dithiolate). The zigzag arrangement of Li(+)([12]crown-4)(2) cations in Li(+)([12]crown-4)(2)[Ni(dmit)(2)](-) salt induced weak intermolecular interactions of [Ni(dmit)(2)](-) dimers, whose magnetic spins were isolated from each other. The molecular arrangements of cations and anions in M(+)([12]crown-4)(2)[Ni(dmit)(2)](-) salts (M(+) = Na(+), K(+), and Rb(+)) were isostructural to each other. In the case of Na(+)([12]crown-4)(2)[Ni(dmit)(2)](-), the space group C2/m changed to C2/c with a lowering in temperature from 298 to 100 K. This structural change occurred at 222.5 K as a first-order phase transition. The space group C2/m (T = 298 K) in the salt K(+)([12]crown-4)(2)[Ni(dmit)(2)](-) also changed to C2/c (T = 100 K), which transition occurred at 270 K. Crystal structural analyses at 298 and 100 K revealed changes in both supramolecular cation conformation and [Ni(dmit)(2)](-) anion arrangements. The transition from C2/m to C2/c crystals generated a dipole moment in the Na(+)([12]crown-4)(2) and K(+)([12]crown-4)(2) structures, which were reconstructed to cancel the net dipole moment of the C2/c crystals. These cation transformations led to changes in intermolecular interactions between the [Ni(dmit)(2)](-) anions via structural rearrangements. The crystal structure of C2/c was stabilized in Rb(+)([12]crown-4)(2)[Ni(dmit)(2)](-) at 298 K. The [Ni(dmit)(2)](-) configuration in these salts with the C2/c space group was a one-dimensional uniform chain, which showed the temperature-dependent magnetic susceptibility of a one-dimensional linear Heisenberg antiferromagnetic chain.     

N(CH2CH2NH3)3][U3O2F13].2H2O: a novel organically templated mixed-valent uranium oxyfluoride with a hybrid network structure

The synthesis and characterization of a novel mixed-valent uranium oxyfluoride is described; the inorganic network consists of 2-D [U(2)F(10)](2)(-) sheets constructed from corner- and edge-sharing U(IV)F(9) tricapped trigonal prisms and 1-D [UO(2)F(3)](-) chains constructed from edge-sharing U(VI)O(2)F(5) pentagonal bipyramids with the organic cations and water molecules between the sheets. This is the first example with a hybrid network structure in the system of uranium fluoride or oxyfluoride. The variable-temperature magnetic susceptibility confirms the oxidation state of the uranium ions. Crystal data follow: C(6)H(25)N(4)O(4)F(13)U(3), monoclinic, space group P2(1) (No. 4); a = 8.6876(4) A, b = 7.3158(4) A, c = 16.3376(8) A, beta = 93.7285(9) degrees , V = 1036.2(2) A(3), and Z = 2.     

Structural polarity induced by cooperative hydrogen bonding and lone-pair alignment in the molecular uranyl iodate Na2[UO2(IO3)4(H2O)

Na2[UO2(IO3)4(H2O)] has been synthesized under mild hydrothermal conditions. Its structure consists of Na+ cations and [UO2(IO3)4(H2O)](2-) anions. The [UO2(IO3)4(H2O)](2-) anions are formed from the coordination of a nearly linear uranyl, UO2(2+), cation by four monodentate IO(3-) anions and a coordinating water molecule to yield a pentagonal bipyramidal environment around the uranium center. The water molecules form intermolecular hydrogen bonds with the terminal oxo atoms of neighboring [UO2(IO3)4(H2O)](2-) anions to yield one-dimensional chains that extend down the b axis. There are two crystallographically unique iodate anions in the structure of Na2[UO2(IO3)4(H2O)]. One of these anions is aligned so that the lone-pair of electrons is also directed along the b axis. The overall structure is therefore polar, owing to the cooperative alignment of both the hydrogen bonds and the lone-pair of electrons on iodate. The polarity of the monoclinic space group C2 (a = 11.3810(12) A, b = 8.0547(8) A, c = 7.6515(8) A, beta = 90.102(2) degrees , Z = 2, T = 193 K) found for this compound is consistent with the structure. Second-harmonic generation of 532 nm light from a 1064 nm laser source yields a response of approximately 16x alpha-SiO2.     

2,6-Mes(2)C(6)H(3)](2)Ga(+)Li[Al(OCH(CF(3))(2))(4)](2)(-) (Mes = 2,4,6-Me(3)C(6)H(2)): A compound containing a linear unsolvated two-coordinate gallium cation

The title compound [2,6-Mes(2)C(2)H(3)](2)Ga(+)Li[Al(OCH(CF(3))(2))(4)](2)(-), 1, containing a linear two-coordinate gallium cation, has been obtained by metathesis reaction of [2,6-Mes(2)C(2)H(3)](2)GaCl with 2 equiv of Li[Al(OCH(CF(3))(2))(4)] in C(6)H(5)Cl solution at room temperature. Compound 1 has been characterized by (1)H, (13)C((1)H), (19)F, and (27)Al NMR spectroscopy and X-ray crystallography. Compound 1 consists of isolated [2,6-Mes(2)C(6)H(3)](2)Ga(+) cations and Li[Al(OCH(CF(3))(2))(4)](2)(-) anions. The C-Ga-C angle is 175.69(7) degrees, and the Ga-C distances are 1.9130(14) and 1.9145(16) A. The title compound is remarkably stable, is only a weak Lewis acid, and polymerizes cyclohexene oxide.     

Unusual syntheses, structures, and electronic properties of compounds containing ternary, T3-type supertetrahedral M/Sn/S anions [M5Sn(mu3-S)4(SnS4)4](10- (M = Zn, Co)

A recently discovered series of quaternary compounds of the general type [K(m)(ROH)(n)()][M(x)Sn(y)()Se(z)] (R = H, Me), containing ternary anions with [SnSe(4)](4-)-coordinated transition metal centers (M = Co, Mn, Zn, Cd, Hg) has now been extended by the synthesis and characterization of the two ortho-thiostannate-coordinated species, [Na(10)(H(2)O)(32)][M(5)Sn(mu(3)-S)(4)(SnS(4))(4)].2H(2)O (M = Zn (1), Co (2)). The central structural motifs of compounds 1 and 2 are highly charged [M(5)Sn(mu(3)-S)(4)(SnS(4))(4)](10-) anions, being the first T3-type supertetrahedral ternary anions reported to date. The exposure of single crystals of 2 to a dynamic vacuum for several hours resulted in the reversible formation of a partially dehydrated, but still monocrystalline material of the composition [Na(10)(H(2)O)(6)][Co(5)Sn(mu(3)-S)(4)(SnS(4))(4)] (3). The loss of 28 of the 34 water molecules only slightly affects the internal structure of the ternary anion in 3 and leads to a significant compacting of the crystal structure with closer linkage of the [Co(5)Sn(5)S(20)](10-) cluster units via the Na(+) cations. Magnetic measurements on 3 show that the ground state of the Co/Sn/S cluster is S = 1/2, indicating a significant antiferromagnetic coupling between the Co centers, which has also been rationalized by DFT investigations of the electronic situation in the ternary subunits of 1-3.     

Design and synthesis of luminescence chemosensors based on alkynyl phosphine gold(I)-copper(I) aggregates

Receptor-containing polynuclear mixed-metal complexes of gold(I)-copper(I) 1-3 based on a [{Au(3)Cu(2)(C≡CPh)(6)}Au(3){PPh(2)-C(6)H(4)-PPh(2)}(3)](2+) (Au(6)Cu(2)) core with benzo-15-crown-5, oligoether and urea binding sites were designed and synthesized, respectively. These complexes exhibited remarkably strong red emission at ca. 619-630 nm in dichloromethane solution at room temperature upon photoexcitation at λ > 400 nm, with the emission quantum yield in the range 0.59-0.85. The cation-binding properties of 1 and 2 and the anion-binding properties of 3 were studied using UV-vis, emission and (1)H NMR techniques. Complex 1, with six benzo-15-crown-5 pendants, was found to show a higher binding preference for K(+), with a selectivity trend of K(+)? Cs(+) > Na(+) > Li(+). The addition of metal ions (Li(+), Na(+), K(+) and Cs(+)) to complex 1 led to a modest emission enhancement with a concomitant slight blue shift in energy and well-defined isoemissive points, which is attributed to the rigidity of the structure and the inhibited PET (photo-induced electron transfer) process from the oxygen to the aggregate as a result of the binding of the metal ion. The six urea receptor groups on complex 3 were found to form multiple hydrogen bonding interactions with anions, with the positive charge providing additional electrostatic interaction for anion-binding. The anion selectivity of 3 follows the trend F(-) > Cl(-)≈ H(2)PO(4)(-) > Br(-) and the highest affinity towards F(-) is attributed to the stronger basicity of F(-), as well as its good size match with the cavity of the urea pocket.     

From linear inorganic chains to helices: chirality in the M(pyz)(H(2)O)(2)MoO(2)F(4) (M = Zn,Cd) compounds

Cd(C(4)H(4)N(2))(H(2)O)(2)MoO(2)F(4) (C(4)H(4)N(2) = pyrazine, pyz) was synthesized via hydro(solvato)thermal methods and characterized by single-crystal X-ray diffraction methods (P3(2)()21, no. 154, Z = 3, a = 7.4328(7) A, c = 16.376(2) A). Both of the known M(pyz)(H(2)O)(2)MoO(2)F(4) (M = Zn, Cd) compounds are comprised of trans-M(pyz)(2)(OH(2))(2)F(2) and cis-MoO(2)F(4) octahedra that share fluoride vertices to form helical chains along the 3-fold screw axes. Individual chains are bridged to six symmetry-equivalent helices through metal-pyrazine and OH(2)...F and OH(2)...O hydrogen bonds. Structural comparisons of similar oxyfluoride chains demonstrate that they can be varied from linear to helical through (1) the replacement of pyridine or pyrazine by H(2)O molecules and (2) the substitution of cis-directing MoO(2)F(4)(2-) anions in place of trans-directing WO(2)F(4)(2-) or TiF(6)(2-) anions. Infrared absorption (IR) measurements for M = Cd show two distinct O-H stretches corresponding to hydrogen-bonded O-H...F and O-H...O groups. Contrastingly for M = Zn, IR measurements exhibit O-H stretches for averaged hydrogen-bonded O-H...(O/F) groups, free (unbound) O-H groups, and higher energy Mo-F stretches. The IR data suggest a small fraction of the O-H...F hydrogen bonds are broken in the M = Zn analogue as a result of the racemic twinning. Both compounds exhibit nonlinear optical behavior, with second harmonic generation (SHG) intensities, relative to SiO(2), of approximately 0.25 ( = 0.28 pm/V) for the racemically twinned Zn(pyz)(H(2)O)(2)MoO(2)F(4) and approximately 1.0 ( = 0.55 pm/V) for the enantiopure Cd(pyz)(H(2)O)(2)MoO(2)F(4).     

Synthesis and redox properties of triarylmethane dye cation salts of anions [M6O19]2- (M = Mo, W)

Four salts have been isolated combining the triarylmethane dye cations pararosaniline (PR(+)) and crystal violet (CV(+)) with the hexametalates [M(6)O(19)](2-) (M = Mo, W). A new hexatungstic acid H(2)[W(6)O(19)]·4dma (dma = dimethylacetamide) was isolated and is a useful synthon for hexatungstate salts. Single-crystal X-ray diffraction confirmed the presence of PR(+) and [Mo(6)O(19)](2-) ions in [PR](2)[Mo(6)O(19)]·6dmf (dmf = dimethylformamide). A number of charge-assisted hydrogen bonds N-H···O exist between the cation -NH(2) functions and the anion oxygen atoms. Comparative cyclic voltammetry of salts [A]Cl (A = PR, CV), [Bu(4)N](2)[M(6)O(19)](2-) and A(2)[M(6)O(19)] was established in MeCN and Me(2)SO solutions and of solids in contact with the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide [emim][tfsa]. In the molecular solvents, the reversible potential for the process [Mo(6)O(19)](2-/3-) is less negative than the first reduction processes of the dye cations. In contrast, that for [W(6)O(19)](2-/3-) is more negative. Spectro-electrochemistry and bulk electrolysis experiments reveal significantly different pathways in the two cases. In contrast, in the [emim][tfsa] medium, a positive shift in reduction potential of at least 400 mV is seen for the anion processes but relatively little change for the dye cation processes. This means that initial reduction of the anions always precedes that of the dyes, providing significant simplification of the complex voltammetric data. Chemically modified electrodes can be used in the ionic liquid because of slow dissolution kinetics. However, reduced anion salts dissolve rapidly, allowing dissolved phase electrochemistry to be examined. The electrochemistries of the oxidized salts A(2)[M(6)O(19)] are essentially those of the individual ions, although low level interaction of A(+) with reduced anions [M(6)O(19)](3-,4-) is evident. The work establishes protocols for synthesis and handling of intensely absorbing and relatively insoluble salts which can now be applied to systems containing more complex polyoxometalate anions.