The 2-D double layer structures of indium–benzenemulticarboxylate coordination polymers with green fluorescence

Two coordination polymers, [In(btc)(2,2′-bpy)(H₂O)]_n · nH₂O (1) and [In₂(btec)(2,2′-bpy)₂Cl₂]_n (2) (H₃btc = 1,3,5-benzenetricarboxylic acid, H₄btec = 1,2,4,5-benzenetetracarboxylic acid, 2,2′-bpy = 2,2′-bipyridine), have been prepared under hydrothermal conditions. Single-crystal X-ray diffraction analyses reveal that compounds 1 and 2 consist of two-dimensional double layer structures with (3, 3) grids and (4, 2) grids, respectively. The grids along two different directions in 1 are of the opposite chirality, while the interactions of double-layer sheets in 2 create a three-dimensional supramolecular network with one-dimensional tunnels. The additional green luminescences for both 1 and 2 in the solid state at low temperature imply the red shift of emission energy in the compounds, which may derive from LMCT. Their X-ray powder diffractions and thermogravimetric analyses are also discussed.     

New coordination polymers based on a novel polynitrile ligand: Synthesis,structure and magnetic properties of the series [M(tcnoetOH)2(4,4′-bpy)(H2O)2] (tcnoetOH− = [(NC)2CC(OCH2CH2OH)C(CN)2]−; M = Fe,Co and Ni)

A novel polynitrile anionic ligand, tcnoetOH^?(=[(NC)₂CC(OCH₂CH₂OH)C(CN)₂]^?), has been synthesized by a one-pot reaction from a cyclic acetal and malononitrile. This ligand has been successfully used to prepare, with 4,4′-bpy as co-ligand, a novel series of coordination polymers formulated as [M(tcnoetOH)₂(4,4′-bpy)(H₂O)₂] with M(II) = Fe (1), Co (2) and Ni (3). These isostructural compounds present a linear chain structure consisting of octahedrally coordinated metal ions bridged by trans 4,4′-bpy ligands. The coordination sphere of the metal ions is completed with two terminal tcnoetOH^? ligand and two water molecules. The magnetic properties indicate that the three compounds are paramagnetic, as expected from the long 4,4′-bpy bridge connecting the metal atoms. Their magnetic properties have been fitted with a model of isolated ions including a zero field splitting for the Fe(II) and Ni(II) derivatives.     

Expanding the 4,4′-bipyridine ligand: Structural variation in {M(pytpy)2}2+ complexes (pytpy = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine,M = Fe,Ni, Ru) and assembly of the hydrogen-bonded,one-dimensional polymer {[Ru(pytpy)(Hpytpy)]}n3n+

The solid state structures of [Ni(1)₂][NO₃]₂ · 2MeOH · 2H₂O, [Fe(1)₂][ClO₄]₂ · 2MeOH · 0.5H₂O, [Ru(1)₂][PF₆]₂ and [Ru(1)₂][PF₆][NO₃] (1 = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine) are presented and the structural variation observed for the {M(1)₂}²⁺ unit is discussed. Protonation of the pendant pyridine group in [Ru(1)₂]²⁺ leads to the formation of a hydrogen-bonded, one-dimensional polymer [{Ru(1)(H1)}_n]³ⁿ⁺ exemplifed by the solid-state structure of [{Ru(1)(H1)}{Fe(NCS)₆} · 1.25H₂O]_n.     

Two novel erbium (III) coordination polymers with 5-nitroisophthalic acid: Syntheses and crystal structures and thermal stabilities

Two new coordination polymers, {[Er(5-nip)_1.5(2,2′-bipy)](H₂O)₂}_n (1) and {[Er(5-nip)₂] (4,4′-H₂bipy)_0.5}_n (2) (5-nip = 5-nitroisophthalic acid, 2,2′-bipy = 2,2′-bipyridyl, 4,4′-bipy = 4,4′-bipyridyl), have been synthesized by the hydrothermal reactions of erbium nitrate, 5-nitroisophthalic acid (5-H₂nip) and 2,2′-bipyridyl (for 1), and erbium nitrate, 5-nitroisophthalic acid and 4,4′-bipyridyl (for 2). X-ray diffraction analysis indicates that complex 1 exhibits a two-dimensional layer structure, while complex 2 displays a 3D architecture sustained by the strong hydrogen-bond interactions between the protonated 4,4′-bipyridyl and the carboxyl oxygen atom from [Er₂(5-nip)₄]²⁻ with 2D layer structure, and 4,4′-bipyridyl as the guest molecules exist in bilayer channel. They are characterized by the elemental analysis and IR spectroscopy. The studies for the thermal stabilities of the two complexes show that complex 2 is more stable than complex 1.     

Syntheses,structures, and magnetic properties of heterobimetallic complexes based on tetracyanometallic building blocks

Two tetracyanometalate building blocks, [Fe(5,5′-dmbipy)(CN)₄]^? (2) and [Fe(4,4′-dmbipy)(CN)₄]^? (3) (5,5′-dmbipy = 5,5′-dimethyl-2,2′-bipyridine; 4,4′-dmbipy = 4,4′-dimethyl-2,2′-bipyridine), and two cyano-bridged heterobimetallic complexes, [Cu₂(bpca)₂(H₂O)₂Fe₂(5,5′-dmbipy)₂(CN)₈] · 2[Cu(bpca)Fe(5,5′-dmbipy)(CN)₄] · 4H₂O (4) and [Cu(bpca)Fe(4,4′-dmbipy)(CN)₄]_n (5) (bpca = bis(2-pyridylcarbonyl)amidate), have been synthesized and structurally characterized. Complex 4 contains two dinuclear and one tetranuclear heterobimetallic clusters in an asymmetric unit whereas the structure of complex 5 features a one-dimensional heterobimetallic zigzag chain. The Cu(II) ion is penta-coordinated in the form of a distorted square-based pyramid. Magnetic studies show ferromagnetic coupling between Cu(II) and Fe(III) ions with g = 2.28, J₁ = 2.64 cm^?1, J₂ = 5.40 cm^?1 and TIP = ?2.36 × 10^?3 for complex 4, and g = 2.17, J = 4.82 cm^?1 and zJ′ = 0.029 cm^?1 for complex 5.     

Synthesis,crystal structures and properties of three rare earth substituted germanotungstates: M/[α-GeW11O39] (M = Nd,Eu, and Tb)

Three new polyoxometalate compounds based on the lacunary Keggin anion [α-GeW₁₁O₃₉]^8? and the rare earth cations (Ln = Nd^III, Eu^III, Tb^III), [(CH₃)₄N]_2.5H_7.5[Eu(GeW₁₁O₃₉)(H₂O)₂]₂ · 4.5H₂O (1), [(CH₃)₄N]₂H₈[Tb(GeW₁₁O₃₉)(H₂O)₂]₂ · 2.5H₂O (2) and [Nd_0.5(H₂O)₂]H_0.5[Nd₂(GeW₁₁O₃₉)(DMSO)₂(H₂O)₈] · 5.5H₂O (3), have been synthesized and characterized by elemental analysis, inductively coupled plasmas (ICP) analysis, IR spectroscopy, single-crystal X-ray diffraction. The solid-state structures of compounds 1 and 2 consist of one-dimensional linear wires built of [α-GeW₁₁O₃₉]^8? anions connected by Eu³⁺/Tb³⁺ cations, while in compound 3, the introduction of the organic molecules DMSO (DMSO = dimethyl sulphoxide) leads to a double-parallel chainlike structure constructed by two linear wires {[Nd(1)(GeW₁₁O₃₉)(DMSO)(H₂O)₂]^5?}_n linked by Nd³⁺ coordination cation. Furthermore, the luminescent property of compound 1 and the thermal stability of compound 3 were also studied.     

Ionic luminescent cyclometalated Ir(III) complexes with polypyridine co-ligands

Two novel ligands containing a functionalized N ∧ N chelating moiety (pbpy-OBut and tpy-COOH, respectively) were treated with [Ir(ppy)₂(μ-Cl)]₂ (ppy = 2-(2-pyridyl)phenyl), leading to the cationic cyclometalated complexes [Ir(ppy)₂(pbpy-OBut)]⁺ (2) (pbpy-OBut = 4-{4′-(4-phenyloxy)-6′-phenyl-2,2′-bipyridyl}butene) and [Ir(ppy)₂(tpy-COOH)]⁺ (3) (tpy-COOH = 4′-(4-carboxyphenyl)-2,2′:6′,2″-terpyridine). Complexes 2 and 3 exhibit intense room temperature luminescence both in solution and as solid films. Assignment of the emissive behavior to a ³LLCT (ppy-to-N ∧ N) excited state is proposed.     

Linear homobimetallic 4-thioacetyl-substituted NCN pincer palladium(II) and platinum(II) complexes with N-bidentate connecting units (NCN = [C6H2(CH2NMe2)2-2,6-R-4]−)

The synthesis and characterization of homobimetallic palladium and platinum complexes of type [(Me(O)CS-4-NCN–M ← N^∩N → M–NCN-4-SC(O)Me](OTf)₂ (Me(O)CS-4-NCN = [C₆H₂(CH₂NMe₂)₂-2,6-SC(O)Me-4]^?; N^∩N = 4,4′-bipyridine (bipy); M = Pd, 12; M = Pt, 13) is reported. The required bifunctional thio-acetyl NCN pincer starting compound NC(Br)N-4-SC(O)Me (2) has been synthesized by the consecutive reactions of NC(Br)N–I (I-1-C₆H₂(CH₂NMe₂)₂-3,5-Br-4) (1) with ^tBuLi, S₈ and Me(O)CCl, respectively. Chemoselective metallation at the C_aryl–Br bond was achieved by the reaction of 2 with the palladium(0) source [Pd₂(dba)₃] (3) (dba = dibenzylidene acetone). Treatment of thus formed [Pd(NCN-4-SC(O)Me)(Br)] (4) with [AgOTf] (8) (OTf = triflate, OSO₂CF₃) gave [Pd(NCN-4-SC(O)Me)(H₂O)][OTf] (9) which was further reacted with 0.5 equiv. of 4,4′-bipyridine (11a) to afford rigid-rod structured 12. When [Pt(tol)₂(SEt₂)]₂ (5) (tol = 4-tolyl) was used instead of 3, then 13 was produced via the in situ formation of [PtBr(NCN-4-SC(O)Me)] (7) and [Pt(NCN-4-SC(O)Me)(H₂O)][OTf] (10). Another possibility to synthesize 7 relied upon the subsequent reaction of 1 with 0.5 equiv. of 5 to give [PtBr(NCN-4-I)] (6) which further reacted with ^tBuLi, 1/8 S₈ and Me(O)CCl to afford 7. The cyclic voltammograms of 2, 7, and 13 are discussed.Complex 7 was structurally characterized by single crystal X-ray crystallography. Organometallic 7 crystallizes with three independent molecules in the asymmetric unit and displays a monomeric structure as commonly encountered in d⁸-metal pincer chemistry.     

Synthesis and biological evaluation of platinum–acridine hybrid agents modified with bipyridine non-leaving groups

The use of 2,2′-bipyridines (4,4′-R₂-2,2′-bpy; R = H, Me, OMe, CF₃) as non-leaving groups (L–L) in platinum–acridinylthiourea conjugates, [PtCl(L-L)(ACRAMTU)](NO₃)₂, has been investigated. All bpy-substituted complexes (2–5) show micromolar activity in HL-60 (leukemia) and H460 (lung) cancer cell lines but proved to be significantly less potent than the prototypical compound (1) containing aliphatic ethane-1,2-diamine. NMR and mass spectrometry data indicate that bpy accelerates the reaction of platinum with DNA nitrogen, but the resulting adducts are more labile than those formed by the prototype.     

Synthesis,crystal structure and magnetic properties of the spin crossover system [Fe(pq)3]2+

Three new compounds formulated (ClO₄)₂[Fe(pq)₃] (1), (BF₄)₂[Fe(pq)₃] · EtOH (2) and {(ClO₄)[MnCr(C₂O₄)₃][Fe(pq)₂(H₂O)₂]} (3), where pq is 2,2′-pyridylquinoline, have been synthesised and characterised. Despite the different crystal packing exhibited by 1 and 2, the cationic species [Fe(pq)₃]²⁺ are structurally quite similar. At 293 K, the Fe–N bond lengths are characteristic of the iron(II) in the high-spin state. In contrast to 1, 2 undergoes a continuous spin transition. Indeed, at 95 K its structure experiences a noticeable change in the Fe–N bonds and angles, i.e. the Fe–N bonds shorten by 0.194 Å on the average. The magnetic behaviour confirms that 1 is fully high-spin in the 4–300 K temperature range while 2 shows a spin transition centred at T_1/2 = 150 K. The corresponding enthalpy, entropy and interaction parameter are ΔH = 7.49 kJ mol^?1, ΔS = 50 J K^?1 mol^?1and Γ = 1.35 kJ mol^?1. Compound 3 has been obtained as a microcrystalline powder. The magnetic properties of 3 point at the occurrence of ferromagnetic coupling below 100 K and the onset of a ferromagnetic ordering below 10 K (Weiss constant equal to 6.8 K). The Mössbauer spectra of 3 show the occurrence of a magnetic order at T ? 4.2 K.     

Syntheses and crystal structures of trimethyltin(IV) coordination polymers based on mixed ligands of 5-nitroisophthalate and 2,2′(4,4′)-bipy or phen

The trimethyltin(IV) polymer [(Me₃Sn)₂(nip) · EtOH]_n (1) of 5-nitroisophthalic acid (H₂nip) and its three derivatives with mixed organic N-donor ligands 2,2′-bipy [(Me₃Sn)₂(nip) · 2H₂O] · [(Me₃Sn)₂(nip) · H₂O] · 2(2,2′-bipy) (2) 4,4′-bipy {[(Me₃Sn)₂(nip)]₂(4,4′-bipy)}_n (3) or phen [(Me₃Sn)₂(nip) · H₂O] · (phen) (4) have been synthesized by the reaction of trimethyltin(IV) chloride and H₂nip when sodium ethoxide was added in the presence of 2,2′-bipy 4,4′-bipy or phen. All complexes 1–4 were characterized by elemental, IR, ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopy and X-ray crystallography analyses. Crystal, data collection and structure refinement parameters for complexes 1, 2, 3 and 4 are shown in Table 1, Table 2, respectively. The X-ray data showed the geometries of all the tin atoms in complexes 1–4 are trigonal bipyramidal. The X-ray analysis of 1 showed that the structure was a polymeric infinite chain with neighboring triorganotin centers being linked by dicarboxylate ligands and hydrogen bonds were found between adjacent chains. For 2, two different monomers were found, in one monomer, Me₃Sn were coordinated to both carboxyl groups of the ligand and water molecules were coordinated to the two Sn(IV) centers. In the other monomer, water molecules were coordinated to only one Sn center. Co-crystallized2,2′-bipy was found in 2 and a 2D supermolecular structure was formed via O–H⋯O and O–H⋯N (N atoms derived from 2,2′-bipy) hydrogen bonds. In 3 however, a 2D polymeric block was formed due to the inversion center of the 4,4′-bipy. For 4, due to the O–H⋯O and O–H⋯N (N atoms derived from phen) hydrogen bonds and intermolecular Sn⋯O bonds, a 2D polymeric structure was formed.     

Linkage isomerism in the metal complex hexa(thiocyanato)rhenate(IV): Synthesis and crystal structure of (NBu4)2[Re(NCS)6] and [Zn(NO3)(Me2phen)2]2[Re(NCS)5(SCN)]

The linkage isomers [Re(NCS)₆]^2? and [Re(NCS)₅(SCN)]^2? are obtained by the reaction of [ReBr₆]^2? with NCS^? in dimethylformamide. Some differences in the chemical behavior allowed their separation and structural characterization in the form of (NBu₄)₂[Re(NCS)₆] (1) and [Zn(NO₃)(Me₂phen)₂]₂[Re(NCS)₅(SCN)] (2), respectively (Bu = n-C₄H₉ and Me₂phen = 2,9-dimethyl-1,10-phenanthroline).     

New pentafluorophenyl complexes with phosphine-amide ligands

A series of nickel(II) and palladium(II) complexes containing one or two pentafluorophenyl ligands and the phosphino-amides o-Ph₂PC₆H₄CONHR [R = ⁱPr (a), Ph (b)] displaying different coordination modes have been synthesised. The chelating ability of these ligands and the influence of both coligands and the metal centre in their potential hemilabile behaviour have been explored. The crystal structure of (b) has been determined and reveals N–H⋯O intermolecular hydrogen bonding. Bis-pentafluorophenyl derivatives [M(C₆F₅)₂(o-Ph₂PC₆H₄CO-NHR)] [M = Ni; R = ⁱPr (1a); R = Ph (1b); M = Pd; R = ⁱPr (2a); R = Ph (2b)] in which (a) and (b) act as rigid P, O-chelating ligands were readily prepared from the labile precursors cis-[M(C₆F₅)₂(PhCN)₂]. X-ray structures of (1a), (1b) and (2a) have been established, allowing an interesting comparative structural discussion. Dinuclear [{Pd(C₆F₅)(tht)(μ-Cl)}₂] reacted with (a) and (b) yielding the monopentafluorophenyl complexes [Pd(C₆F₅)Cl{PPh₂(C₆H₄–CONH–R)}] (R = ⁱPr (3a), Ph (3b)) that showed a P, O-chelating behaviour of the ligands, confirmed by the crystal structure determination of (3a). New cationic palladium(II) complexes in which (a) and (b) behave as P-monodentate ligands have been synthesised by reacting them with [{Pd(C₆F₅)(tht)(μ-Cl)}₂], stoichiometric Ag(O₃SCF₃) and external chelating reagents such as cod [Pd(C₆F₅)(cod){PPh₂(C₆H₄-CONH-R)}](O₃SCF₃)(R = ⁱPr (4a), Ph (4b)) and 2,2′-bipy [Pd(C₆F₅)(bipy){PPh₂(C₆H₄-CONH-R)}](O₃SCF₃) (R = ⁱPr (5a), Ph (5b)). When chloride abstraction in [{Pd(C₆F₅)(tht)(μ-Cl)}₂] is promoted by means of a dithioanionic salt as dimethyl dithiophospate in the presence of (a) or (b), the corresponding neutral complexes [Pd(C₆F₅){S(S)P(OMe)₂}{PPh₂(C₆H₄-CONH-R)}] (R = ⁱPr (6a), Ph (6b)) were obtained.     

Methylnickel compounds containing 2-phosphinylethanolato ligands – Syntheses,properties, and ethene coupling reactions

Combining dimethylphosphinylethanols HO(R¹R²)CCH₂PMe₂ (1: R¹ = R² = C₆H₅; 2: R¹ = R² = 4-OMe–C₆H₄; 5: R¹ = R² = 4-NMe₂–C₆H₄) with methyl(methoxo)(trimethylphosphine)nickel gave mononuclear methyl(trimethylphosphine)nickel(chelate) compounds 7–9. Ligand 6 (R¹ = Me, R² = 4-OMe–C₆H₅) afforded a dinuclear methylnickel compound 14. By reacting (TMEDA)lithium-dimethylphosphinylmethanide with ketones OC(R¹R²), the dimethylphosphinylethanols HO(R¹R²)CCH₂PMe₂ (3: R¹R² = 9-fluorenyl; 4: R¹ = H, R² = C₆H₅) were synthesized as prechelate ligands. Under otherwise similar conditions, the fluorenyl substituted anion in 3 gave rise to a mononuclear complex 10 which was found to act as a source of trimethylphosphine forming dinuclear 11 and at the same time to act as an acceptor of trimethylphosphine forming pentacoordinate 10 · PMe₃. Ni(COD)(PMe₃)₂ was used as a scavenger of PMe₃ in converting 8 or 9 to the dinuclear methylnickel compounds 12 and 13, respectively. Modifying the P,O chelating unit of a methyl nickel compound by introducing 2-phosphinylethanolato ligands leads to novel single-component catalysts for ethene oligomerization showing moderate reactivity and thermal stability.     

Acetato complexes of molybdenum(V): A novel tetranuclear core based on the metal–metal bonded {Mo2O4}2+ units

A series of acetato complexes of molybdenum(V), based on the singly metal–metal bonded {Mo₂O₄}²⁺ structural fragment, has been prepared. A dinuclear (PyH)₃[Mo₂O₄Cl₄(OOCCH₃)] · CH₃CN (1) (PyH⁺ = pyridinium cation, C₅H₅NH⁺) was obtained upon the reaction of (PyH)₅[MoOCl₄(H₂O)]₃Cl₂ with the equimolar solution of pyridine and acetic acid in acetonitrile at ambient conditions. The acetato ligand in 1 is coordinated to a pair of molybdenum atoms in a syn–syn bidentate bridging manner. (PyH)_n[MoOBr₄]_n afforded in an analogous synthetic procedure a tetranuclear cluster, [Mo₄O₈(OOCCH₃)₃(OH)Py₄] · 1/2CH ₃CN · 1/2H₂O (3), with a novel core which may be envisioned as the acetate- and hydroxide-assisted assembly of {Mo₂O₄}²⁺ building blocks. Its structure is presented in terms of known tetranuclear clusters which are also composed of two {Mo₂O₄}²⁺ units. The acetato ligands in 3 adopted apart from bidentate bridging binding modes also a monodentate one. Partial substitution of chlorido ligands in (PyH)₃[Mo₂O₄Cl₄(OOCCH₃)] · CH₃CN (1) with pyridine resulted in a neutral [Mo₂O₄Cl(OOCCH₃)Py₃] · PrⁱOH · Py (2) which retained the original acetate coordination. The title compounds were fully characterized by X-ray diffraction studies and infrared vibrational spectroscopy.     

Photophysical studies of hetero-bischelated complexes of rhodium(III) containing 2,2′-dipyridylamine

Four mixed-ligand complexes, cis-Rh[(bipy)(HDPA)Cl₂]Cl (1), cis-[Rh(phen)(HDPA)Cl₂]Cl (2), cis-[Rh(bipy)(DPA)Cl₂] (3), and cis-[Rh(phen)(DPA)Cl₂] (4) (where bipy = 2,2′-bipyridine, phen = 1,10-phenantroline, HDPA = 2,2′-dipyridylamine, and DPA = the deprotonated form of 2,2′-dipyridylamine) have been synthesized and characterized. In slightly acidic solution and at low temperature (77 K), both complexes 1 and 2 show a broad, symmetric and structureless red emission with microsecond lifetime identified as dd* phosphorescence. In slightly basic solution, the deprotonated complexes (3 and 4) exhibit a broad and asymmetric blue emission, showing no vibrational structure with a lifetime in the order of microseconds. Emission of complex 3 reveals a blue shift of 0.81 μm⁻¹ compared to the emission of complex 1 and that of complex 4 shows a blue shift of 0.77 μm⁻¹ with respect to complex 2. Electrochemical data have also been obtained for the four complexes in CH₃CN. There are two reduction peaks observed for both complexes 1 and 2. Each peak is followed by a one-electron reduction at the metal, with an elimination of chloride during each reduction step, which is in consistent with the dd* phosphorescence assignment for the two complexes. For complexes 3 and 4, only a one-electron reduction process occurs at the metal with an elimination of chloride. Based on the luminescence and electrochemical data, the emission of complexes 3 and 4 are assigned as πd* phosphorescence. Results from density functional theory (DFT) calculations provide theoretical evidence in support of this πd* assignments.     

Dimerisation versus polymerisation: Affects of donor position in isomeric dilithium diamine-bis(phenolate) complexes

The synthesis and structures of isomeric lithium diamine-bis(phenolate) complexes are reported. Deprotonation of the ligands, H₂O₂NN′^tBu [Me₂NCH₂CH₂N(CH₂ArOH)₂, Ar = 3,5-C₆H₂-^tBu₂] and H₂O₂N₂^tBu [HOArCH₂NMeCH₂CH₂NMeCH₂ArOH, Ar = 3,5-C₆H₂-^tBu₂], in diethyl ether affords base-free lithium complexes Li₂O₂NN′^tBu (1) and Li₂O₂N₂^tBu (2) upon solvent removal. The dioxane adduct of (1) exhibits a polymeric structure in the solid-state, whereas the dioxane adduct of (2) possesses a dimeric structure. The syntheses of K₂O₂NN′^tBu (3), K₂O₂N₂^tBu (4), Zr(O₂NN′^tBu)Cl₂ (5) and Y(O₂NN′^tBu)Cl(THF), (6), are also reported. The transition metal complexes were isolated in good yields via salt metathesis reactions using 1 or 3.     

Structural and antitumor activity study of γ-octamolybdates containing aminoacids and peptides

γ-Type octamolybdates of the formulae, Na₄[Mo₈O₂₆(alaO)₂] · 18H₂O (I), Na₄[Mo₈O₂₆(glyglyO)₂] · 15H₂O (II) and Na₄[Mo₈O₂₆(glyglyO)₂] · 12H₂O (III) have been prepared from sodium molybdate in aqueous solution by adding dl-alanine or glycylglycine. Their crystal structures have been determined by X-ray structure analysis. dl-alanine and glycylglycine coordinate molybdenum atom in γ-octamolybdate [Mo₈O₂₆]⁴⁻ anions via monodentate carboxylate-oxygen atom. The prepared octamolybdates were screened for the possible antiproliferative activity on a panel of five tumor cell lines and on a normal cell line. All tested compounds showed a differential cell-growth inhibition in a dose-dependent manner selectively on hepatocellular carcinoma cell line (HepG2) and breast cancer cell line (MCF-7).     

Dicarboxylatodirhodium derivatives of polyoxotungstates

Salts of the new complexes [PW₁₁O₃₉{Rh₂(O₂CR)₂}]⁵⁻; R = Prⁿ (1), CH₂Cl (2), CH₂OH (3), o-C₆H₄OH (4), p-C₆H₄OH (5), and [XW₁₁O₃₉{Rh₂(p-O₂CC₆H₄OH)₂}]⁶⁻; X = Si (6), Ge (7) have been prepared in good yield and characterized by elemental analysis, multinuclear NMR spectroscopy, and structural crystallography of the cesium salts of anions 1 and 5 with chloride ions in axial positions of the dirhodium moiety. The incorporation of the dirhodium group into the Keggin structure significantly increases the hydrolytic kinetic stability of the polyoxotungstates at pH 7–8.5, a result that has implications for the use of such complexes for imaging and for phase determination in structural studies of large biomolecules. Based on NMR studies, the axial sites of the dirhodium moiety of the polytungstate anions are accessible to ligation by molecules such as cysteine, methionine, and isonicotinic acid.     

Tuning magnetic properties using targeted structural distortion: New additions to a family of Mn6 single-molecule magnets

We report the synthesis and magnetic properties of three hexametallic Mn clusters: [Mn₆O₂(Et-sao)₆(O₂C-Naphth)₂(EtOH)₄(H₂O)₂] (1) (HO₂C-Naphth = 1-naphthoic acid, Et-saoH₂ = 2-hydroxyphenylpropanone oxime), [Mn₆O₂(Et-sao)₆(O₂C-Anthra)₂(EtOH)₄(H₂O)₂] · 0.66EtOH · 0.33H₂O (HO₂C-Anthra = anthracene-9-carboxylic acid) (2 · 0.66EtOH · 0.33H₂O) and [Mn₆O₂(Et-sao)₆(O₂CPhCCH)₂(EtOH)₄(H₂O)₂] · 1.7EtOH · 0.3H₂O (HO₂CPhC  CH = 4-ethynylbenzoic acid) (3 · 1.7EtOH · 0.3H₂O). Clusters 1–3 exhibit ferromagnetic exchange between all six Mn^III centres resulting in S = 12 ground spin states. Ac magnetic susceptibility and single crystal micro-SQUID measurements on 1–3 confirm SMM behaviour with barriers to magnetisation reversal of 60.12 (1), 60.10 (2) and 66.79 (3) K.