2D and 3D Coordination Networks of Polynuclear Bismuth Oxido/Hydroxido Sulfonato Clusters from Low Temperature Solid‐State Metathesis Reactions

Synthesis and Characterization of Cerium-Oxo Clusters Capped by Acetylacetonate

Cerium-oxo clusters have applications in fields ranging from catalysis to electronics and also hold the potential to inform on aspects of actinide chemistry. Toward this end, a cerium-acetylacetonate (acac1-) monomeric molecule, Ce(acac)4 (Ce-1), and two acac1--decorated cerium-oxo clusters, [Ce10O8(acac)14(CH3O)6(CH3OH)2]·10.5MeOH (Ce-10) and [Ce12O12(OH)4(acac)16(CH3COO)2]·6(CH3CN) (Ce-12), were prepared and structurally characterized. The Ce(acac)4 monomer contains CeIV. Crystallographic data and bond valence summation values for the Ce-10 and Ce-12 clusters are consistent with both clusters having a mixture of CeIII and CeIV cations. Ce L3-edge X-ray absorption spectroscopy, performed on Ce-10, showed contributions from both CeIII and CeIV. The Ce-10 cluster is built from a hexameric cluster, with six CeIV sites, that is capped by two dimeric CeIII units. By comparison, Ce-12, which formed upon dissolution of Ce-10 in acetonitrile, consists of a central decamer built from edge sharing CeIV hexameric units, and two monomeric CeIII sites that are bound on the outer corners of the inner Ce10 core. Electrospray ionization mass spectrometry data for solutions prepared by dissolving Ce-10 in acetonitrile showed that the major ions could be attributed to Ce10 clusters that differed primarily in the number of acac1-, OH1-, MeO1-, and O2- ligands. Small angle X-ray scattering measurements for Ce-10 dissolved in acetonitrile showed structural units slightly larger than either Ce10 or Ce12 in solution, likely due to aggregation. Taken together, these results suggest that the acetylacetonate supported clusters can support diverse solution-phase speciation in organic solutions that could lead to stabilization of higher order cerium containing clusters, such as cluster sizes that are greater than the Ce10 and Ce12 reported herein.

Bismuth-Polyoxocation Coordination Networks: Controlling Nuclearity and Dimension-Dependent Photocatalysis

Bismuth-oxocluster nodes for metal-organic frameworks (MOFs) and coordination networks/polymers are less prolific than other families featuring zinc, zirconium, titanium, lanthanides, etc. However, Bi³⁺ is non-toxic, it readily forms polyoxocations, and its oxides are exploited in photocatalysis. This family of compounds provides opportunity in medicinal and energy applications. Here, we show that Bi node nuclearity depends on solvent polarity, leading to a family of Bi_x-sulfonate/carboxylate coordination networks with x = 1-38. Larger nuclearity-node networks were obtained from polar and strongly coordinating solvents, and we attribute the solvent's ability to stabilize larger species in solution. The strong role of the solvent and the lesser role of the linker in defining node topologies differ from other MOF syntheses, and this is due to the Bi³⁺ intrinsic lone pair that leads to weak node-linker interactions. We describe this family by single-crystal X-ray diffraction (eleven structures), obtained in pure forms and high yields. Ditopic linkers include NDS (1,5-naphthalenedisulfonate), DDBS (2,2'-[biphenyl-4,4'-diylchethane-2,1-diyl] dibenzenesulphonate), and NH₂-benzendicarboxylate (BDC). While the BDC and NDS linkers yield more open-framework topologies that resemble those obtained by carboxylate linkers, topologies with DDBS linkers appear to be in part driven by association between DDBS molecules. An in situ small-angle X-ray scattering study of Bi₃₈-DDBS reveals stepwise formation, including Bi₃₈-assembly, pre-organization in solution, followed by crystallization, confirming the less important role of the linker. We demonstrate photocatalytic hydrogen (H₂) generation with select members of the synthesized materials without the benefit of a co-catalyst. Band gap determination from X-ray photoelectron spectroscopy (XPS) and UV-vis data suggest the DDBS linker effectively absorbs in the visible range with ligand-to-Bi-node charge transfer. In addition, materials containing more Bi (larger Bi₃₈-nodes or Bi₆ inorganic chains) exhibit strong UV absorption, also contributing to effective photocatalysis by a different mechanism. All tested materials became black with extensive UV-vis exposure, and XPS, transmission electron microscopy, and X-ray scattering of the black Bi₃₈-framework suggest that Bi⁰ is formed in situ, without phase segregation. This evolution leads to enhanced photocatalytic performance, perhaps due to increased light absorption.

Crystal structures of two new divalent transition-metal salts of carboxybenzenesulfonate anions

The structure of hexa­aqua­nickel(II) bis­(3-carb­oxy-4-hy­droxy­benzene­sulfonate) dihydrate consists of alternating layers of inorganic cations and organic anions linked by O—H⋯O hydrogen bonds that also include non-coordinated water mol­ecules of crystallization. The structure of hexa­aqua­cobalt(II) bis­(3-carb­oxy­benzene­sulfonate) dihydrate is also built of alternating layers of complex cations and organic anions without direct coordination to the metal by the protonated carboxyl­ate or unprotonated sulfonate groups. A robust O—H⋯O hydrogen-bonding network involving primarily the coordinated and non-coordinated water mol­ecules and sulfonate groups directs the packing.

Hexa­aqua­nickel(II) bis­(3-carb­oxy-4-hy­droxy­benzene­sulfonate) dihydrate, [Ni(H₂O)₆][C₆H₃(CO₂H)(OH)SO₃]₂·2H₂O, (I), crystallizes in the triclinic space group P with the nickel(II) aqua complexes on centers of inversion. The carboxyl­ate group is protonated and neither it nor the sulfonate group is involved in direct coordination to the metal ions. The structure consists of alternating layers of inorganic cations and organic anions linked by O—H⋯O hydrogen bonds that also include non-coordinated water mol­ecules of crystallization. The first-row divalent transition-metal salts of this anion are reported as both dihydrates and tetra­hydrates, with two distinct structures for the dihydrates that are both layered but differ in the hydrogen-bonding pattern. Compound (I) represents the second known example of one of these structures. Hexa­aqua­cobalt(II) bis­(3-carb­oxy­benzene­sulfonate) dihydrate, [Co(H₂O)₆][C₆H₄(CO₂H)SO₃]₂·2H₂O, (II), also crystallizes in triclinic P with the cobalt(II) aqua complexes on centers of inversion. The structure is also built of alternating layers of complex cations and organic anions without direct coordination to the metal by the protonated carboxyl­ate or unprotonated sulfonate groups. A robust O—H⋯O hydrogen-bonding network involving primarily the coordin­ated and non-coordinated water mol­ecules and sulfonate groups directs the packing. This is the first reported example of a divalent transition-metal salt of the 3-carb­oxy­benzene­sulfonate anion.

The low-temperature triclinic crystal structure of silver 3-sulfo-benzoic acid

Poly[(μ4-3-carboxybenzenesulfonato)silver(I)], Ag(O3SC6H4CO2H) or [Ag(C7H5O5S)] n , has been found to undergo a reversible phase transition from monoclinic to triclinic between 160 and 150 K. The low-temperature triclinic structure (space group P ) has been determined at 100 K. In contrast to the reported room temperature monoclinic structure, in which the nearly equivalent carboxyl-ate C-O distances indicate that the acidic hydrogen is randomly distributed between the O atoms, at 100 K the C-O (protonated) and C=O (unprotonated) bonds are clearly resolved, resulting in the reduction in symmetry from C2/c to P .

Tweaking the Charge Transfer: Bonding Analysis of Bismuth(III) Complexes with a Flexidentate Phosphane Ligand

To account for the charge transfer and covalent character in bonding between P and Bi centers, the electronic structures of [P(C₆H₄-o-CH₂SCH₃)₃BiCl_n]^(3–n)+ (n = 0–3) model species have been investigated computationally. On the basis of this survey a synthetic target compound with a dative P→Bi bond has been selected. Consecutively, the highly reactive bismuth cage [P(C₆H₄-o-CH₂SCH₃)₃Bi]³⁺ has been accessed experimentally and characterized. Importantly, our experiments (single-crystal X-ray diffraction and solid-state NMR spectroscopy) and computations (NBO and AIM analysis) reveal that the P···Bi bonding in this trication can be described as a dative bond. Here we have shown that our accordion-like molecular framework allows for tuning of the interaction between P and Bi centers.

The bonding situation in species with the general formula of [P(C₆H₄-o-CH₂SCH₃)₃BiCl_n]⁽³⁻ⁿ⁾⁺ (n = 0−3) has been investigated computationally, and on this basis a selected example has been accessed synthetically. The structural and solid-state NMR studies reveal that the weak secondary pnictogen interaction in P(C₆H₄-o-CH₂SCH₃)₃BiCl₃ can be tuned into dative bonding by enhancing the charge transfer from the phosphorus to the bismuth center, which is accompanied by a change in the spin−spin coupling mechanism between the ³¹P and ²⁰⁹Bi nuclei.

Synthesis, structural characterisation, and cytotoxicity studies of Bi, W, and Mo containing homo- and hetero-bimetallic polyoxometalates

Three new and different homo- and hetero-bimetallic polyoxometalate (POM) species have been synthesised by simple one-pot synthetic methods utilising naturally occurring bismite (Bi₂O₃) (or Bi(NO₃)₃·5H₂O) and aryl sulfonic acids. The POM species isolated are (NH₄)₁₄[Bi₂W₂₂O₇₆]·14H₂O (1·14H₂O), (NH₄)[Bi(DMSO)₇][Mo₈O₂₆]·H₂O (2·H₂O) and [(NH₄)₄(Mo₃₆O₁₀₈(OH)₄·16H₂O)]·45H₂O (3·45H₂O). The compounds have been characterised by X-ray crystallography, energy dispersive X-ray spectroscopy (EDX), powdered X-ray diffraction (PXRD), mass spectrometry (ESI-MS), Raman spectroscopy, thermogravimetric (TGA) and ICP analyis. In vitro cytoxicity and proliferation studies conducted on 1 and 3, highlight the low toxicity of these species.

Multiparameter High-Throughput and in Situ X-ray Diffraction Study of Six New Bismuth Sulfonatocarboxylates: Discovery, Phase Transformation, and Reaction Trends

With the employment of high-throughput methods, the system Bi³⁺/4,8-disulfonyl-2,6-naphthalenedicarboxylic acid (H₄DSNDC)/H₂O/additive (HNO₃ or NaOH) was systematically investigated under hydrothermal reaction conditions. The influence of the molar ratio of the starting materials, pH, and reaction temperature and time was investigated in more than 500 reactions. The product formation is highly sensitive toward small changes of the synthesis parameters, but six new bismuth sulfonatocarboxylates were reproducibly obtained starting from clear solutions of the reactants. All compounds were structurally characterized from single-crystal X-ray diffraction data. Fully deprotonated linker ions are found in [Bi₆O₆(OH)₂(H₂O)₄(DSNDC)] (1), [Bi₂(OH)₂(DSNDC)] (2), [Bi₈O₇(OH)₂(H₂O)₂(DSNDC)₂] (3), and [Bi₇O₅(OH)₃(H₂O)₄(DSNDC)₂]·4H₂O (4), while the presence of larger amounts of acid or short reaction times leads to compounds with noncoordinating -COOH groups, [Bi₂(OH)₂(H₂O)₂(DSNDC)(H₂DSNDC)] (5) and [Bi₆O₄(OH)₄(H₂O)₁₂(H₂DSNDC)₃]· xH₂O (6), respectively. The inorganic building units (IBUs) in all six structures differ substantially from each other; the IBUs found in 2 ({Bi₂(OH)₂}), 5 (BiO₈ polyhedron), and 6 ({Bi₆O₄(OH)₄} cluster) have been reported in the literature, while new IBUs are observed for 1 (chains of composition {Bi₃O₃(OH)}_∞), 3 ({Bi₁₆O₁₄(OH)₄} cluster), and 4 ({Bi₇O₅(OH)₃} cluster). Systematic variation of the reaction temperature and time indicated their distinct influence on product formation. Hence, in situ powder X-ray diffraction measurements at Deutsches Elektronen-Synchrotron, Hamburg, Germany, employing synchrotron radiation were carried out. In all studied in situ reactions, compound 6 is first observed and subsequently transformed to 1, 2, 4, and 5, depending on the reaction time and temperature as well as concentration of the starting materials.