A host–guest hybrid framework with Anderson anions as template: synthesis, crystal structure and photocatalytic properties

Fabrication of bimetallic-doped materials derived from a Cu-based complex for enhanced dye adsorption and iodine capture

In this work, we used Cu(II) ions, a bis-pyridyl-bis-amide ligand [N,N'-bis(4-pyridinecarboxamide)-1,2-cyclohexane (4-bpah)], and an aromatic dicarboxylic acid [1,4-cyclohexanedicarboxylic acid (H2CHDA)] to construct a 1D binuclear Cu-based complex, namely {[Cu3(4-bpah)(CHDA)3(H2O)]·2H2O}n (1). Moreover, we also developed a facile method to synthesize two monometallic/bimetallic-doped materials which were derived from the Cu complex (C-N-1 and C-V-1, which were doped with nitrogen and vanadium, respectively). The as-synthesized derived materials were fully characterized and the iodine sorption/release capabilities were investigated in detail. We performed iodine adsorption experiments on the two monometallic/bimetallic-doped materials and found that C-N-1 and C-V-1 possess highly efficient adsorption activities for the adsorption of iodine from solution. The C-N-1 and C-V-1 complexes exhibited remarkable adsorption capacities of 1141.60 and 1170.70 mg g-1, respectively, for iodine from a cyclohexane solution. Moreover, the dye adsorption properties of C-N-1 and C-V-1 were also investigated in detail. The obtained C-N-1 and C-V-1 exhibit effective dye uptake performances in water solution. The adsorption of Congo red (CR) on a single metal carbon material C-N-1 doped with heteroatoms reached equilibrium within 240 min and reached an adsorption capacity of 1357.00 mg g-1 and the adsorption capacities of C-V-1 for methylene blue (MB), gentian violet (GV), rhodamine B (RhB), and CR at room temperature were found to be 187.60, 190.60 and 108.10 and 1501.00 mg g-1 in 180 min, respectively. By comparison, we found that doping vanadium could play an important role in the adsorption processes. The adsorption capacity of C-V-1 (containing the vanadium in its structure) was relatively higher than that of C-N-1, which indicated that the introduction of non-noble metals may effectively tune the adsorption kinetics activity and the introduction of noble metals can change the surface electronegativity of porous carbon materials, thus leading to significantly improved adsorption capabilities.

Modular enhancement of circularly polarized luminescence in Pd2A2B2 heteroleptic cages

Metal-mediated assembly allows us to combine an achiral emissive ligand A with different chiral ligands (such as B) in a non-statistical fashion, obtaining Pd₂A₂B₂ heteroleptic cages showing circularly polarized luminescence (CPL). By using the 'shape complementary assembly' (SCA) strategy, the cages are exclusively obtained as cis-Pd₂A₂B₂ stereoisomers, as confirmed by NMR, MS and DFT analyses. Their unique chiroptical properties derive from the synergy of all the building blocks. Ligand B imparts the chiral information of its aliphatic backbone, comprising two stereogenic sp³ carbon centres, to the overall structure, causing CD and CPL signal induction for the chromophore on ligand A. The heteroleptic cage shows CPL with a |g_lum| value of 2.5 × 10^-3, which is 3-times higher than that for a progenitor based on aromatic helical building block H, thus opening a rational route towards optimizing the CPL properties of self-assembled nanostructures in a modular way.

A novel 3D Zn-coordination polymer based on a multiresponsive fluorescent sensor demonstrating outstanding sensitivities and selectivities for the efficient detection of multiple analytes

A novel and unusual 3D luminescent coordination polymer (CP) [Zn₂(3-bpah)(bpta)(H₂O)]·3H₂O (1), where 3-bpah denotes N,N'-bis(3-pyridinecarboxamide)-1,2-cyclohexane and H₄bpta denotes 2,2',4,4'-biphenyltetracarboxylic acid, was successfully synthesized via hydrothermal methods from Zn(II) ions and 3-bpah and bpta ligands. The structure of this CP was investigated via powder X-ray diffraction (PXRD) analysis along with single crystal X-ray diffraction. Notably, 1 exhibits remarkable fluorescence behavior and stability over a wide pH range and in various pure organic solvents. More importantly, 1 can become an outstanding candidate for the selective and sensitive sensing of Fe³⁺, Mg²⁺, Cr₂O₇^2-, MnO₄^-, nitrobenzene (NB) and nitromethane (NM), at an extremely low detection limit. The changes in the fluorescence intensity exhibited by these six analytes in the presence of 1 over a wide pH range indicate that this polymer can be an excellent luminescent sensor. To the best of our knowledge, 1 is a rare example of a CP-based multiresponsive fluorescent sensor for metal cations, anions, and toxic organic solvents.

Synthesis and Structural and Spectroscopic Studies of a pH-Neutral Argentic Chelate Complex: Tribasic Silver (III) Bisperiodate

The preparation of stable hypervalent metal complexes containing Ag(III) has historically been challenging due to their propensity for reduction under ambient conditions. This work explores the preparation of a tripotassium silver bisperiodate complex as a tetrahydrate via chemical oxidation of the central silver atom and orthoperiodate chelation. The isolation of the chelate complex in high yield and purity was achieved via acidimetric titration. The comprehensive physiochemical characterization of the tribasic silver bisperiodate included single crystal X-ray diffraction, thermogravimetric and differential scanning calorimetry, and infrared and ultraviolet-visible spectroscopy. Infrared and UV-visible absorption spectra (λ_max 255 and 365 nm) were in good agreement with historically prepared pentabasic diperiodatoargentate chelate complexes. The C2/c monoclinic distorted square planar structure of the bis-chelate complex affords a mutually supportive framework to both Ag(III) and I(VII), conferring stability under both thermal and long-term ambient conditions. Thermal analysis of the tribasic silver bisperiodate complex identified an endothermic mass loss, ΔH = +278.35 kJ/mol, observed at 139.0 °C corresponding to a solid-state reduction of silver from Ag(III) to Ag(I). Under ambient conditions, no significant degradation was observed over a 12 month period (P = 0.30) for the silver bisperiodate complex in a solid state, with an observed half-life of τ_1/2 = 147 days in a pH-neutral aqueous solution.

Co(ii) coordination polymers constructed from a bent chiral linker: influencing framework topology using co-ligands

The reaction of a semi-rigid chiral ligand with Co(ii) and dipyridyl co-ligands of varying length yielded a series of 2D coordination frameworks, with the topology of the network mediated by the length of the co-ligands.

Application of flexible bis-pyrazine–bis-amide ligands to construct various polyoxometalate-based metal–organic complexes

Five novel polyoxometalates-based metal–organic complexes constructed from different types of polyanions and flexible bis-pyrazine–bis-amide ligands with different spacer lengths have been hydrothermally synthesized and structurally characterized.

Polyoxometalate-directed assembly of various multinuclear metal–organic complexes with 4-amino-1,2,4-triazole and selective photocatalysis for organic dye degradation

Five POM-based metal–organic complexes ranging from 0D trinuclear cluster, 1D chain, 2D network, to 3D framework have been successfully prepared in the presence/absence of citric or boric acid.