Novel Three-Dimensional Organic–Inorganic Heterometallic Hybrid Built by Sandwich-Type Tetra-Mn-Substituted Germanotungstates through Mixed 3d and 4f Metal Linkers

The reaction of trivacant Keegin germanotungstate [A-α-GeW₉O₃₄]^10– with Mn²⁺ and Ce⁴⁺ cations in the presence of oxalate ligand under hydrothermal conditions led to the isolation of a novel organic–inorganic hybrid 3d–4f heterometallic germanotungstate K₄Na₄[Ce₂(ox)₃(H₂O)₂]₂{[Mn(H₂O)₃]₂[Mn₄(GeW₉O₃₄)₂(H₂O)₂]·14H₂O (<b>1</b>) (ox = oxalate), which has been characterized by elemental analysis, IR spectroscopy, thermogravimetric (TG) analysis, and single-crystal X-ray crystallography. Interestingly, each tetra-Mn^II-substituted sandwich-type unit acts as 14-dentate ligands to link eight Ce³⁺ centers and six Mn²⁺ centers further into a three-dimensional (3D) architecture. The 3D structure can be considered as two parts: one is the two-dimensional layer formed by sandwich-type [Mn₄(H₂O)₂(GeW₉O₃₄)₂]^12– fragments and Mn²⁺ linkers; the other layer is constructed from Ce³⁺ cations and oxalate bridges, and the two layers are combined together alternately through W–O–Ce–O–W linkers, resulting in the 3D framework. Notably, <b>1</b> exhibits the first 3d–4f 3D organic–inorganic hybrid framework constructed by sandwich-type TM-substituted polyoxoanions and mixed 3d and 4f metal linkers in POM chemistry

Novel Three-Dimensional Organic–Inorganic Heterometallic Hybrid Built by Sandwich-Type Tetra-Mn-Substituted Germanotungstates through Mixed 3d and 4f Metal Linkers

The reaction of trivacant Keegin germanotungstate [A-α-GeW₉O₃₄]^10– with Mn²⁺ and Ce⁴⁺ cations in the presence of oxalate ligand under hydrothermal conditions led to the isolation of a novel organic–inorganic hybrid 3d–4f heterometallic germanotungstate K₄Na₄[Ce₂(ox)₃(H₂O)₂]₂{[Mn(H₂O)₃]₂[Mn₄(GeW₉O₃₄)₂(H₂O)₂]·14H₂O (<b>1</b>) (ox = oxalate), which has been characterized by elemental analysis, IR spectroscopy, thermogravimetric (TG) analysis, and single-crystal X-ray crystallography. Interestingly, each tetra-Mn^II-substituted sandwich-type unit acts as 14-dentate ligands to link eight Ce³⁺ centers and six Mn²⁺ centers further into a three-dimensional (3D) architecture. The 3D structure can be considered as two parts: one is the two-dimensional layer formed by sandwich-type [Mn₄(H₂O)₂(GeW₉O₃₄)₂]^12– fragments and Mn²⁺ linkers; the other layer is constructed from Ce³⁺ cations and oxalate bridges, and the two layers are combined together alternately through W–O–Ce–O–W linkers, resulting in the 3D framework. Notably, <b>1</b> exhibits the first 3d–4f 3D organic–inorganic hybrid framework constructed by sandwich-type TM-substituted polyoxoanions and mixed 3d and 4f metal linkers in POM chemistry

Glycosides with galloyl groups from <i>Balakata baccata</i> and their antineuroinflammatory activities

Seven new glycosides (1 − 7) with galloyl groups and two known kaempferol glycosides (8 and 9) were obtained from the overground parts of Balakata baccata. The structures of the new compounds were determined by comprehensive spectroscopic analyses. The rarely seen allene moiety in compounds 6 and 7 were described by detailed analysis of 1D and 2D NMR data. The antineuroinflammatory effect of all the isolates was assessed through inhibiting nitric oxide (NO) production in lipopolysaccharide (LPS)-induced BV-2 microglial cells. Compounds 1, 2, 6, and 7 showed potent inhibitory activities with IC50 values of 25.7, 17.2, 15.5 and 24.4 μM, respectively, compared with the positive control minocycline (IC50 = 16.1 μM).</p

Decoration of Covalent Polyoxometalate-Organic Frameworks with Pt Nanoparticles and Multiwalled Carbon Nanotubes for Simultaneous Electrochemical Detection of Hydroquinone and Catechol

Hydroquinone (HQ) and catechol (CC) are isomers with similar structures, which destroyed ecosystem balance and human health at an alarming rate. Therefore, it is critical to monitor HQ and CC in the environment simultaneously. Herein, a sensitive electrochemical sensor based on multiwalled carbon nanotubes and covalent polyoxometalate-organic frameworks (CPOFs) modified by nanoparticles (PtNPs@CPOFs-MWCNTs) was designed for the simultaneous detection of HQ and CC. Polyoxometalates (POMs) have been extensively studied in the area of electrochemical sensors because of rich reversible multielectron redox behavior. The porous and long stick-shaped CPOFs was synthesized by solvothermal Schiff base reaction, with NH2-POM-NH2 and 2,5-dimethoxy-phenyl-1,4-diformaldehyde as monomers. Using the porosity and large surface area of CPOFs, the obtained PtNPs@CPOFs nanocomposite showed an improved distribution of electroactive sites. At the same time, highly conductive MWCNTs was incorporated to guarantee the conductivity. Consequently, PtNPs@CPOFs-MWCNTs was obtained to improve the electrical conductivity and electrocatalytic activity. The results showed that the PtNPs@CPOFs-MWCNTs/GCE performed a wide range and low detection limit toward the detection of HQ and CC simultaneously. Furthermore, PtNPs@CPOFs-MWCNTs/GCE also had great stability and anti-interference ability