Search

Advances in polyoxometalate (POM) self-assembly chemistry are always accompanied by new developments in molecular blocks. The exploration and discovery of uncommon building blocks offer great possibilities for generating unprecedented POM clusters. An intriguing SbIII–WVI-cotemplated antimonotungstate [H2N(CH3)2]11Na[SbW9O33]Er2(H2O)2Sb2[SbWVIW15O57]·22H2O (1) was synthesized, which comprises a classical trivacant Keggin [SbW9O33]9–({SbW9}) fragment and an unclassical lacunary Dawson-like [SbWVIW15O57]15–({SbWVIW15}) subunit. Notably, the Dawson-like {SbWVIW15} subunit is the first example of a [SbO3]3–and [WVIO6]6–mixed-heteroatom-directing POM segment. Hexacoordinated [WVIO6]6–can not only serve as the heteroatom function but its additional oxygen sites can also link to lanthanide, main-group metal, and transition-metal centers to form the innovative structure. {SbWVIW15} and {SbW9} subunits are joined by the heterometallic [Er2(H2O)2Sb2O17]22–cluster to give rise to an asymmetric sandwich-type architecture. To further realize its potential application in electrochemical sensing, a conductive 1@rGO composite was obtained by the electrochemical deposition of 1with graphene oxide (GO). Using a 1@rGO-modified glassy carbon electrode as the working electrode, an electrochemical biosensor for detecting the antidepressant drug paroxetine (PRX) was successfully constructed. This work can provide a viable strategy for synthesizing mixed-heteroatom-directing POMs and demonstrates the application of POM-based materials for the electrochemical detection of drug molecules.

Organic–inorganic hybrid metal–oxide clusters have been pursued for many years, benefiting from their abundant structures and prominent performances. Upon our exploration, a family of unusual mixed-heteroatom (SbIII, PIII)-directing lanthanoid (Ln)-inserted heteropolyoxotungstates (Ln-HPOTs), [(CH3)2NH2]2Na7H3[Ln4(HPIII)W8(H2O)12(H2ptca)2O28][SbIIIW9O33]2·27H2O [Ln = Ce3+(1), La3+(2), Pr3+(3)], functionalized by 1,2,3-propanetricarboxylic acid (H3ptca) was achieved. The intriguing trimeric [Ln4(HPIII)W8(H2O)12(H2ptca)2O28][SbIIIW9O33]212–polyanion was established by two trivacant [B-α-SbIIIW9O33]9–segments mounted on both sides and one rare [HPIIIW4O18]8–segment at the bottom, which are bridged via an organic–inorganic hybrid [W4Ln4(H2O)12O10(H2ptca)2]14+central moiety. Such Ln-HPOTs involving dual-heteroatom-directing mixed building blocks, and even simultaneously modified by tricarboxylic ligands, are rather unseen in polyoxometalate chemistry. Moreover, the detection of 17β-estradiol through a 1-based electrochemical biosensor has been explored, demonstrating a low detection limit (7.08 × 10–14M) and considerable stability.

Eighteen new Lycopodiumalkaloids, lycosquarrines A–R (1–18), and eight known alkaloids were isolated from the aerial parts of Phlegmariurus squarrosus. Compounds 1–5and 19, identified from natural sources for the first time, are uncommon lycopodine-type alkaloids with β-oriented H-4. Pentacyclic 4and 5represent the first examples of 5,12- and 5,11-epoxy Lycopodiumalkaloids, respectively, and an epoxide-opening cyclization reaction is suggested to be a key step in their biosynthesis. Compound 18possesses the same carbon skeleton as carinatine A (22), which was previously reported as a unique Lycopodiumalkaloid with a 5/6/6/6 ring system. X-ray crystallographic data analysis was used to determine the absolute configuration of 18, leading to the establishment of the absolute configuration of 22by comparison of the ECD spectra. An anti-acetylcholinesterase activity assay showed that 11and 20exhibited inhibitory activities with IC50values of 4.2 and 2.1 μM, respectively.

A double-oxalate-bridging tetra-Gd3+containing divacant Lindqvist dimeric isopolytungtate Na10[Gd2(C2O4)(H2O)4(OH)W4O16]2·30H2O (Gd4W8) was obtained based on the reaction of Na2WO4·2H2O, H2C2O4, and GdCl3in aqueous solution. Its dimeric polyoxoanion is established by two divacant Lindqvist [W4O16]8–segments connected by a rectangular tetra-nuclearity [Gd4(C2O4)2(H2O)8(OH)2]6+cluster. Notably, neighboring trinuclear [Na3O4(H2O)11]5–clusters are interconnected to construct a picturesque 1-D sinusoidal Na–O cluster chain. The most outstanding characteristic is that 1-D sinusoidal Na–O cluster chains combine [Gd2(C2O4)(H2O)4(OH)W4O16]210–polyoxoanions together, giving rise to an intriguing 3-D extended porous framework. The red emitter Eu3+ions and green emitter Tb3+ions are first codoped into Gd4W8to substitute Gd3+ions for the exploration of the energy transfer (ET) mechanism between Eu3+and Tb3+ions and the color-tunable PL property in the isopolytungtate system. The PL emission spectra and decay lifetime measurements of the Eu3+/Tb3+codoped Gd4W8system illustrate that under excitation at 370 nm, Tb3+ions can transfer energy to Eu3+ions. When the molar concentration of Tb3+ions is fixed at 0.9 and that of the Eu3+ions gradually increases from 0.01 to 0.08, the calculated ET efficiency (ηET) from Tb3+to Eu3+ions increases from 7.9% for Gd0.36Tb3.6Eu0.04W8to 67.3% for Gd0.08Tb3.6Eu0.32W8. The energy transfer mechanism (Tb3+→ Eu3+) is a nonradiative dipole–dipole interaction. Furthermore, upon excitation at 370 nm, Eu4W8and Tb4W8show visible red- and green-emitting lights, respectively. When codoping trace amounts of Eu3+ions in Tb4W8, under excitation at 370 nm, Tb3.92Eu0.08W8displays near white-light emission.

Template-directed assembly of giant cluster-based nanomaterials is an everlasting theme in cluster science. In this work, ethylenediamine tetramethylphosphonic acid [H8EDTPA = (POCH2(OH)2)4C2H4N2] and [B-α-SbW9O33]9–were, respectively, used as an organic template and an inorganic template to prepare an organophosphonic acid-regulating PV–SbIII-heteroatom-inserted polyoxotungstate aggregate [H2N(CH3)2]5Na11H9[CeW4O10(HEDTPA)SbW15O50][B-α-SbW9O33]2·36H2O (1). Noteworthily, organophosphonic acid ligand not only works as an organic template leading to the assembly of a [HEDTPASbW15O50]14–building block but also further bridges the sandwich-type [CeW4O10(B-α-SbW9O33)2]11–entity. To extend its potential application in electrochemical sensing properties, we prepared a three-dimensional 1@EGO composite (EGO = reduced graphene oxide functionalized by ethylenediamine) with porous architecture and a prominent conducting ability. Furthermore, the 1@EGO composite was explored as a modification material for glassy carbon electrodes to build a dual-signal readout electrochemical aptasensor for carcinogens, which shows much better detection performance for aflatoxin B1 compared with traditional single-signal biosensors