Polyoxometalates Surface Research Articles

Molecular Recognition on the Multisite Binding Surface of the Keplerate {Mo72Fe30} Giving Supramolecular Texturing and Modulating the Function of Guest Molecules.

Molecular recognition underlies structure formation in supramolecular architectures either in materials or in living systems. Here, we used the nanoscale nontoxic Keplerate-type polyoxometalate (POM) {Mo72Fe30} as a template for the recognition of two different guest molecules [tetracycline (TC) and doxorubicin (DOX)] on the textured surface. By means of single crystal X-ray analysis and X-ray photoelectron spectroscopy (XPS), we revised the key features of the {Mo72Fe30} structure, showcasing the guest dimolybdenum units' {Mo2} location under the hexagonal pores and dynamic exchange of these units during dissolution in an aqueous medium. Based on the clarified POM structure, we demonstrated how the small differences between the TC and the DOX molecules can be recognized by the Keplerate surface, revealing the nature of the binding sites─{Mo6}/{FeO6} for TC and {FeO6} for DOX. Furthermore, using the Monte-Carlo method, we calculated the statistical distribution of the guest molecules in the stoichiometric compounds {Mo72Fe30}@TC12 and {Mo72Fe30}@DOX12, displaying the supramolecular ordering of the DOX species and randomization of the TC as a result of different coordinations to the POM surface. The produced {Mo72Fe30}@TC12 and {Mo72Fe30}@DOX12 associates were evaluated for bioactivity, showing how their interaction with POM can modulate the biological function of guest molecules.

Thickness-dependent electronic relaxation dynamics in solution-phase redox-exfoliated MoS2 heterostructures.

Electronic relaxation dynamics of solution-phase redox-exfoliated molybdenum disulfide (MoS2) monolayer and multilayer ensembles are described. MoS2 was exfoliated using polyoxometalate (POM) reductants. This process yields a colloidal heterostructure consisting of MoS2 2D sheet multilayers with surface-bound POM complexes. Using two-dimensional electronic spectroscopy, transient bleaching and photoinduced absorption signals were detected at excitation/detection energies of 1.82/1.87 and 1.82/1.80eV, respectively. Approximate 100-fs bandgap renormalization (BGR) and subsequent defect- and phonon-mediated relaxation on the picosecond timescale were resolved for several MoS2 thicknesses spanning from 1 to 2 L to ∼20 L. BGR rates were independent of sample thickness and slightly slower than observations for chemical vapor deposition-grown MoS2 monolayers. However, defect-mediated relaxation accelerated ∼10-fold with increased sample thicknesses. The relaxation rates increased from 0.33 ± 0.05 to 1.2 ± 0.1 and 3.1 ± 0.4ps-1 for 1-2 L, 3-4 L, and 20 L fractions. The thicknesses-dependent relaxation rates for POM-MoS2 heterostructures were modeled using a saturating exponential function that showed saturation at thirteen MoS2 layers. The results suggest that the increased POM surface coverage leads to larger defect density in the POM-MoS2 heterostructure. These are the first descriptions of the influence of sample thickness on electronic relaxation rates in solution-phase redox-exfoliated POM-MoS2 heterostructures. Outcomes of this work are expected to impact the development of solution-phase exfoliation of 2D metal-chalcogenide heterostructures.

Computational Investigation of the Intermolecular Interactions between Decatungstate Acid and CX2O (X=H, F, Cl, and Br)

AbstractThis study explores intermolecular interactions between the polyoxometalate (POM) compound, decatungstate acid, and CX2O (X=H, F, Cl, and Br). Initial optimizations were conducted using the PBE0 and M06‐2X /Lanl2DZ level of theory, renowned for adsorption studies. Computational results revealed a notable sequential increase in binding affinity for reactive compounds on POM surfaces optimized with PBE0, TPSSH, M06‐2X, CAM‐B3LYP, and ωB97XD/Lanl2Dz methods. Interestingly, the findings indicated a high binding affinity between reactive compounds and POM surfaces, affirming M06‐2X functional suitability for studying decatungstate acid interactions. Additionally, adsorption energy (Eads) values were negative, indicating stable adsorption processes. Careful examination of quantum theory of atoms in molecules (QTAIM), natural charge calculations, and hybridization calculations unveiled impressive intermolecular interactions, with non‐covalent interactions (NCIs) revealing deep blue iso‐surfaces in (CH2O@POM) and (CF2O@POM) complexes, indicating significant electrostatic force of interaction and presence of hydrogen bond interactions, enhancing POM surface‘s gas interaction capacity and smooth sensing. The analyzed complexes displayed slight increases in HOMO‐LUMO energy gap compared to POM, with the order of increase as follows: CH2O@POM (0.0819 eV)>CF2O@POM (0.0772 eV)>CBr2O@POM (0.0747 eV)>CCl2O@POM (0.0705 eV), suggesting POM′s suitability as an adsorbent. The study‘s major findings reveal the effective adsorption of CBr2O and CH2O facilitated by hydrogen bond interactions on the POM surface, making decatungstate acid a potential adsorbent for removing polluting gases from the atmosphere.

Covalent Grafting of Eosin Y to the Giant Keplerate {Mo132} through an Organosilicon Linker in Homogeneous Regime

The template effect of giant polyoxometalates (POM) shows promising results towards the supramolecular design of hybrid materials suitable for photocatalytic reactions. Here, we demonstrate a novel synthetic approach for covalently grafting the xanthene dye eosin Y (EY) to the nanoscale Keplerate POM {Mo132} via an organosilicon linker (3-aminopropyltrimethoxysilane, APTMS) in a homogeneous regime. Using a phase transfer agent, tetrabutylammonium bromide, we solubilize the Keplerate POM modified with six {Si(CH2)3NH2} groups, {Mo132}@Si6, in a series of organic solvents—acetonitrile, acetone, tetrahydrofuran, and dichloromethane—to perform post-functionalization by using an NHS-ester of EY. Both IR and Raman spectroscopy affirm the preservation of the POM’s structure and showcase an amide bond formation between POM and EY in the obtained conjugate {Mo132}@Si6@EY@TBA. Grafting’s success is observed through significant downfield shifting of EY’s aromatic protons’ signals on the 1H NMR spectrum as compared to the spectra of EY and EY-NHS. The current synthetic approach enables us to exercise precise control of the stoichiometry in the POM-dye conjugates—1:1 for the POM-EY system—as confirmed by elemental analysis. Comprehensive photophysical analysis of {Mo132}@Si6@EY@TBA by means of UV-Vis and steady-state and time-resolved fluorescence measurements points to an existing strong interaction between molecular orbitals of EY and {Mo132}, leading to a photoinduced electron transfer, partial fluorescence quenching, and elongation of the excited state’s lifetime. These findings demonstrate that using APTMS as an organosilicon linker in tandem with the Keplerate POM as a nanoscale template can be readily applied as a routine synthetic procedure for grafting various organic dyes or other organic molecules bearing a carboxylic group in their structure to the giant POM surface in a variety of aprotic organic solvents.

The Electrostatic‐Mediated Formation of a Coordination Complex: the Trapping and Release of an Antitumor Drug with an Anthracycline Core from {Mo72Fe30}‐Based Ensembles

AbstractThis article studies the binding of the antitumor drug doxorubicin (DOX) with the nanocluster polyoxometalate (POM) {Mo72Fe30}, the latter serving as the drug carrier. The formation of a stoichiometric complex POM@(DOX)12 was observed in aqueous media. Using the Stern‐Volmer technique, we found the binding constant and free Gibbs energy for this interaction. The produced complex POM@(DOX)12 was examined with ultraviolet‐visible (UV‐Vis), fluorescence (steady state and life‐time), infrared (IR) and X‐ray photoelectron spectroscopy (XPS), which revealed the stoichiometry of complex and a key role of {Mo3Fe3} host pores on the POM surface to DOX binding. DOX's ability to intercalate into DNA after binding with the {Mo72Fe30} was investigated using a pH typical for blood (7.4). A pH‐dependent release of DOX from POM@(DOX)12 was demonstrated (rate constant is 3.3×10−4 s−1). Finally, we showed that the immobilization of doxorubicin on the POM's surface can reduce undesired side effects.

Organic-Inorganic Hybrid Films of the Sulfate Dawson Polyoxometalate, [S2W18O62]4-, and Polypyrrole for Iodate Electrocatalysis.

The Dawson-type sulfate polyoxometalate (POM) [S2W18O62]4- has successfully been entrapped in polypyrrole (PPy) films on glassy carbon electrode (GCE) surfaces through pyrrole electropolymerization. Films of varying POM loadings (i.e., thickness) were grown by chronocoulometry. Film-coated electrodes were then characterized using voltammetry, revealing POM surface coverages ranging from 1.9 to 11.7 × 10-9 mol·cm-2, and were stable over 100 redox cycles. Typical film morphology and composition were revealed to be porous using atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy, and the effects of this porosity on POM redox activity were probed using AC impedance. The hybrid organic-inorganic films exhibited a good electrocatalytic response toward the reduction of iodate with a sensitivity of 0.769 μA·cm-2·μM-1.

(Digital) Ionic Conduction Mechanism and Design of Metal–Organic Framework Based Quasi-Solid-State Electrolytes

Recently, anionic metal–organic frameworks (MOFs) with superior ionic conductivity and Li+ transference numbers have opened a new avenue in the development of quasi-solid-state electrolytes (QSSEs). Given the superior performance and the characterization challenges associated with transport property measurements, it is vitally important to understand the Li+ transport and conduction mechanisms of this new prototype of QSSEs. In this presentation, we will discuss the theoretical and experimental investigation of two polyoxometalate (POM) -based MOFs, [(MnMo6)2(TFPM)] imine and [(AlMo6)2(TFPM)] imine , as QSSEs. Classical molecular dynamics coupled with quantum chemistry and grand canonical Monte Carlo are utilized to model the corresponding diffusion and ionic conduction in the two materials. Using different approximate levels of ion diffusion behavior, the primary ionic conduction mechanism was identified as solvent-assisted hopping (>77%), revealing the critical role of the solvent in MOF-based QSSEs. Detailed static and dynamic solvation structures were obtained to interpret Li+ motion with high spatial and temporal resolution. We found that the local charge distribution on POM surface largely determines the interaction between Li+ and the framework. Based on the prevalent mechanism of Li+ motion, we propose a hypothesized MOF design with a non-interpenetrating structure that is expected to achieve 6–8 times better ionic conduction performance (1.6–1.7 mS cm−1) than the current state-of-the-art (0.19–0.35 mS cm−1), approaching the conductivity range of liquid electrolytes. Figure 1

Polyoxometalate-Supported Copper(I)-Pyrazole Complex: Unusual Stability, Geometrical Isomers, Organic Transformation, and Computation.

We have described the synthesis and characterization of a polyoxometalate (POM)-supported copper(I)–pyrazole complex, [CuI(C15H12N2)2] [PW12O40{CuI(C15H12N2)2}2]·CH3OH (1). There are three Cu(I)–pyrazole coordination complexes in compound 1, out of which two are supported by the {PW12O40}3– Keggin POM by coordinate covalent bonds from the POM surface through oxygen donors to the Cu(I) centers of two Cu(I) complexes and one remains uncoordinated to the POM surface, acting as a cationic complex species in the crystals of 1. The POM-coordinated Cu(I) complexes have a T-shaped geometry, and the uncoordinated Cu(I) complex is a linear one. During the solvothermal synthesis of compound 1, remarkably, the associated 1,5-diphenylpyrazole ligand is formed from cinnamaldehyde phenylhydrazone through oxidative cyclization at the cost of Cu(II) reduction to Cu(I), and then, these two (copper(I) and pyrazole ligand) form the coordination complex. Compound 1 undergoes desolvation on heating the single crystals of compound 1 at 55 °C in the aerial atmosphere with the formation of the desolvated compound [CuI(C15H12N2)2][PW12O40{CuI(C15H12N2)2}2] (2). Interestingly, when an aqueous suspension of compound 1 is bubbled with O2 gas at room temperature, it undergoes solid-to-solid transformation, resulting in the formation of the compound [CuI(C15H12N2)2]3[PW12O40] (3). Compounds 1, 2, and 3 have been characterized by routine spectral analyses (including cyclic voltammetry and X-ray photoelectron spectroscopy (XPS) studies) and unambiguously by single-crystal X-ray crystallography. We have performed density functional theory (DFT) calculations on compound 1 to understand the rationale of its unusual stability toward oxidation.

Functionalized polyoxometalate microspheres ensure selective adsorption of phosphoproteins and glycoproteins.

Lacunary polyoxometalate (POM), [PW9O34]9-, grafts with a boronic acid group attached via an organosilane bridge assemble into microspheres, PW9-Si-APBA. The oxygen-rich and hydrophilic surface of POM facilitates the binding of phosphate groups in phosphoproteins and glycans in glycoproteins. While the metal-oxo in POM provides π-π interactions with the phosphate groups of phosphoproteins, the boronic acid group specifically binds to glycoproteins via the cis-diols of glycans. Therefore, these multi-driving forces ensure the selective adsorption of phosphoproteins and glycoproteins by PW9-Si-APBA microspheres in biological sample matrixes, even in the presence of very high protein abundance, i.e., BSA, at mass ratio of β-ca/IgG/OVA/BSA = 1 : 1 : 1 : 200.

Modulation of Self-Separating Molecular Catalysts for Highly Efficient Biomass Transformations.

The energetically viable fabrication of stable and highly efficient solid acid catalysts is one of the key steps in large‐scale transformation processes of biomass resources. Herein, the covalent modification of the classical Dawson polyoxometalate (POMs) with sulfonic acids (‐SO3H) is reported by grafting sulfonic acid groups on the POM's surface followed by oxidation of (3‐mercaptopropyl)trimethoxysilane. The acidity of TBA6‐P2W17‐SO3H (TBA=tetrabutyl ammonium) has been demonstrated by using 31P NMR spectroscopy, clearly indicating the presence of strong Brønsted acid sites. The presence of TBA counterions renders the solid acid catalyst as a promising candidate for phase transfer catalytic processes. The TBA6‐P2W17‐SO3H shows remarkable activity and selectivity, excellent stability, and great substrate compatibility for the esterification of free fatty acids (FFA) with methanol and conversion into biodiesel at 70 °C with >98 % conversion of oleic acid in 20 min. The excellent catalytic performance can be attributed to the formation of a catalytically active emulsion, which results in a uniform catalytic behavior during the reaction, leading to efficient interaction between the substrate and the active sites of the catalyst. Most importantly, the catalyst can be easily recovered and reused without any loss of its catalytic activity owing to its excellent phase transfer properties. This work offers an efficient and cost‐effective strategy for large‐scale biomass conversion applications.

Aggregation Patterns in Low- and High-Charge Anions Define Opposite Solubility Trends.

Molecular dynamics simulations in aqueous solution reveal the existence of two distinct patterns of aggregation in low and high charge density Lindqvist-type polyoxometalates (POMs). Our results indicate the presence of contact and solvent-shared ion pairs and specific and preferential interactions of alkalis with POMs. Highly charged POMs are capable of breaking apart the Li+ and Cs+ solvation shell, thus enhancing the formation of long-lived alkali-POM contact ion pairs, where alkalis act as an electrostatic "glue" forming large oligomers. Stronger ion pair interactions for Li+ than for Cs+ promote lower solubility for Li+ than for Cs+, evoking anomalous solubility trends. Lower charge density POMs are not capable of disrupting the Li+ solvation shell and only solvent-shared ion pairs are formed, whereas for Cs+, contact ion pairs exist. The large number of oxygen atoms in the POM surface enhances the hydrogen bonds between POM and water, thus promoting aggregation. In this case, aggregation follows normal solubility trends. Thus, aggregation depends on the strength of ion pair interactions, the capacity of POM to disrupt alkali's solvation shell, and the contact surface area between the solvent and POM.

A thermodynamic model of non-ionic surfactants' micellization in the presence of polyoxometalates

Polyoxometalates (POMs) are nanometric metal−oxide anions with an unmatched range of chemical and physical properties. During the past decade, significant efforts have been made to study POM surface activity and self-assembly properties that are essential for catalysis applications and for producing organic−inorganic hybrid materials. A previous work highlighted the tungstosilicate (SiW12O404−) and tungstophosphate (PW12O403−) Keggin POM anions' spontaneous and noncovalent adsorption at the micellar surface of non-ionic surfactants. In this study, the critical micelle concentrations (CMC) of two non-ionic surfactants, the n-octyl-β-glucoside (C8G1) and the tetraethylene glycol monooctyl ether (C8E4), were measured in the presence of POMs, and we propose herein thermodynamic models to explain an increase or a decrease of the CMC depending on the choice of the POM/surfactant couple.

Formation and characterization of charge coupled structure of polyoxometalate particles and a GaAs-based nanowire for readout of molecular charge states

To investigate the molecular charge dynamics of polyoxometalate (POM) molecules, we formed and characterized a charge coupled structure with POM molecular particles and a GaAs-based nanowire. In our system, the charge sensitivity was locally increased by capacitive coupling between a metal tip and the POM particle. Surface dispersion of POM particles on the GaAs nanowire was carried out in a controlled manner by choosing an appropriate solvent and POM concentration. We found that, after POM surface dispersion, the current in the GaAs nanowire remarkably increased by charging the POM particles using a conductive atomic force microscopy tip. The current change strongly depended on humidity of the measurement environment. The nanowire current under capacitive coupling between the conductive tip and the POM particle on the nanowire surface showed steps with a height of approximately 70 nA, suggesting that multiple hole charging and discharging occurred in the particle in a synchronized manner.

Polyoxometalate-Supported Bis(2,2'-bipyridine)mono(aqua)nickel(II) Coordination Complex: an Efficient Electrocatalyst for Water Oxidation.

A polyoxometalate (POM)-supported nickel(II) coordination complex, [NiII(2,2'-bpy)3]3[{NiII(2,2'-bpy)2(H2O)}{HCoIIWVI12O40}]2·3H2O (1; 2,2'-bpy = 2,2'-bipyridine), has been synthesized and structurally characterized. We could obtain a relatively better resolved structure from dried crystals of 1, NiII(2,2'-bpy)3]3[{NiII(2,2'-bpy)2(H2O)}{HCoIIWVI12O40}]2·H2O (D1). Because the title compound has been characterized with a {NiII(2,2'-bpy)2(H2O)}2+ fragment coordinated to the surface of the Keggin anion ([H(CoIIW12O40]5-) via a terminal oxo group of tungsten and the [NiII(2,2'-bpy)3]2+ coordination complex cation sitting as the lattice component in the concerned crystals, the electronic spectroscopy of compound 1 has been described by comparing its electronic spectral features with those of [NiII(2,2'-bpy)2(H2O)Cl]Cl, [NiII(2,2'-bpy)3]Cl2, and K6[CoIIW12O40]·6H2O. Most importantly, compound 1 can function as a heterogeneous and robust electrochemical water oxidation catalyst (WOC). To gain insights into the water oxidation (WO) protocol and to interpret the nature of the active catalyst, diverse electrochemical experiments have been conducted. The mode of action of the WOC during the electrochemical process is accounted for by confirmation that there was no formation/participation of metal oxide during various controlled experiments. It is found that the title compound acts as a true catalyst that has NiII (coordinated to POM surface) acting as the active catalytic center. It is also found to follow a proton-coupled electron-transfer pathway (two electrons and one proton) for WO catalysis with a high turnover frequency of 18.49 (mol of O2)(mol of NiII)-1 s-1.

Nanometer-Size Polyoxometalate Anions Adsorb Strongly on Neutral Soft Surfaces

Polyoxometalates (POMs) are nanometric metal–oxide anions with unique chemical and physical properties. During the past decade, significant efforts have been made to give POMs surface activity and self-assembly properties that are essential for catalysis applications and for producing organic–inorganic hybrid materials. In this work, POMs-based surfactants are produced spontaneously through noncovalent interactions in water by mixing nonionic surfactants with POM. The most common POMs of tungstosilicate and tungstophosphate have indeed an unexpected strong tendency to adsorb on polar and neutral interfaces. Micelles in water and water/air interfaces were investigated by SAXS and ion flotation showing the POM anions adsorbed at the micelle surface and on monolayers of nonionic surfactants. This general property of POM provides a unique opportunity for deeper understanding of many medicinal effects of POMs, i.e., their antiviral and antitumor activities that involve their specific adsorption on biological s...

Spectroscopic studies on tungstoheteropolyanions functionalized by amino acids

The 19 new inorganic–organic hybrid compounds based on Keggin, Preyssler and Wells–Dawson types of tungstoheteropolyanions and fairly complete series of essential amino acids were prepared and the structure of these materials investigated on the basis of CHN analysis and multi-spectroscopic investigations (IR, 1HNMR and 13CNMR). Changes in position and shape of asymmetric stretching vibration bands in finger print regions of polyoxometalates (POMs) were identified in all FT-IR spectra. These changes are related to noncovalent interactions between POM surface oxygen atoms and the bio-organic molecules. In reported compounds, 12 natural amino acids out of 20 (i.e., alanine, glycine, glutamine, asparagine, methionine, cysteine, leucine, arginine, threonine, aspartic acid, disodium glutamate) have participated.

Induced circular dichroism of polyoxometalates via electrostatic encapsulation with chiral organic cations.

To explore the principle of chiral induction in inorganic clusters, chiral organic cations with two stereocenters, R- and S-BPEA, are used to encapsulate a series of polyoxometalates (POMs) bearing different structures and transition absorption bands in aqueous solution, constructing a series of chiral supramolecular complexes. Due to the induction of chiral organic cations, POMs possessing both chiral and achiral structures show an induced circular dichroism (ICD) effect. ICD signals in the absorption bands corresponding to ligand to metal charge transfer (LMCT) transitions, d-d transitions and intervalence charge transfer (IVCT) transitions are observed for different complexes. Moreover, the ICD of the POMs exhibits a direct correlation with the degree of POM distortion and the distance between the chiral center and the POM surface. The encapsulation of POMs with chiral organic cations via electrostatic interactions provides a facile and effective method for constructing optically pure POM-based materials.

Synergistic influence of polyoxometalate surface corona towards enhancing the antibacterial performance of tyrosine-capped Ag nanoparticles

We illustrate a new strategy to improve the antibacterial potential of silver nanoparticles (AgNPs) by their surface modification with the surface corona of biologically active polyoxometalates (POMs). The stable POM surface corona was achieved by utilising zwitterionic tyrosine amino acid as a pH-switchable reducing and capping agent of AgNPs. The general applicability of this approach was demonstrated by developing surface coronas of phosphotungstic acid (PTA) and phosphomolybdic acid (PMA) around AgNPs. Our investigations on Gram negative bacterium Escherichia coli demonstrate that in conjugation with AgNPs, the surface corona of POMs enhances the physical damage to the bacterial cells due to synergistic antibacterial action of AgNPs and POMs, and the ability of tyrosine-reduced AgNPs (AgNPs(Y)) to act as an excellent carrier and stabiliser for the POMs. The further extension of this study towards Gram positive bacterium Staphylococcus albus showed a similar toxicity pattern, whereas these nanomaterials were found to be biocompatible for PC3 epithelial mammalian cells, suggesting the potential of these materials towards specific antimicrobial targeting for topical wound healing applications. The outcomes of this work show that facile tailorability of nanostructured surfaces may play a considerable role in controlling the biological activities of different nanomaterials.

Supramolecular assembly of chiral polyoxometalate complexes for asymmetric catalytic oxidation of thioethers

In this paper, a chiral amphiphilic cation with two stereocenters has been employed to encapsulate a well-known catalytically activated sandwich-type polyoxometalate, Na12[WZn3(H2O)2(ZnW9O34)2], through electrostatic interaction. The prepared chiral organic cation-encapsulated polyoxometalate complexes were found to self-aggregate into spherical supramolecular assemblies with a diameter of ca. 100 nm in the reaction solution. These assemblies, serving as microreactors, exhibited an efficient asymmetric catalytic activity for the oxidation of sulfide with up to 72% enantiomeric excess. The coverage density of chiral organic cations enwrapped on the polyoxometalate surface was proved to have an important influence on the enantioselectivity. Detailed kinetic study of the catalytic process showed that the enantioselectivity of sulfide oxidation was derived from the combination of an ineffective asymmetric sulfoxidation and an effective kinetic resolution of the sulfoxide. The present research strategically offers an understanding for the direct and efficient construction of polyoxometalate based supramolecular catalysts for asymmetric reactions through controlling the surface microenvironment.

Study of the first antibacterial agent pipemidic acid modifying Keggin polyoxometalate

Abstract A new compound based on polyoxometalates (POMs) and the quinolone antibacterial pipemidic acid (HPPA), {[Co(PPA)2]H2[ SiW12O40]}·HPPA·3H2O (1), has been prepared and characterized by elemental analyses, IR and singe crystal X-ray diffraction. The title compound represents the first example of POMs modified by the quinolone antibacterial HPPA, in which the POMs are modified by [Co(HPPA)2] subunits. Its antitumor activity on MCF-7 cells was investigated by the. The results show that the title compound exhibits higher antitumor activity than its parent, which indicates that introduction of M-PPA into the POM surface can increase their antitumor activity and make the compounds to penetrate into the cells easily.