PS Ligands Research Articles

Large-Area Arrays of Polymer-Tethered Gold Nanorods with Controllable Orientation and Their Application in Nano-Floating-Gate Memory Devices.

In this work, it is reported that large-area (centimeter-scale) arrays of non-close-packed polystyrene-tethered gold nanorod (AuNR@PS) can be prepared through a liquid-liquid interfacial assembly method. Most importantly, the orientation of AuNRs in the arrays can be controlled by changing the intensity and direction of electric field applied in the solvent annealing process. The interparticle distance of AuNR can be tuned by varying the length of polymer ligands. Moreover, the AuNR@PS with short PS ligand are favorited to form orientated arrays with the assistance of electric field, while long PS ligands make the orientation of AuNRs difficult. The orientated AuNR@PS arrays are employed as the nano-floating gate of field-effect transistor memory device. Tunable charge trapping and retention characteristics in the device can be realized by electrical pulse with visible light illumination. The memory device with orientated AuNR@PS array required less illumination time (1 s) at the same onset voltage in programming operation, compared to the control device with disordered AuNR@PS array (illumination time: 3 s). Moreover, the orientated AuNR@PS array-based memory device can maintain the stored data for more than 9000 s, and exhibits stable endurance characteristic without significant degradation in 50 programming/reading/erasing/reading cycles.

Effect of Polymer Ligand Conformation on the Self-Assembly of Block Copolymers and Polymer-Grafted Nanoparticles within an Evaporative Emulsion

Precise control of spatial distribution of nanoparticles (NPs) within polymeric materials is critical to build nanostructures with programed functionalities. Herein, we systematically investigate the entropy-driven self-assembly of polystyrene-coated Au NPs (Au@PS NPs) and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymers (BCPs) within a 3D-confined emulsion system. To understand the formation principle of the hybrid particles, four different parameters are examined: (1) the molecular weight of PS ligands (N), (2) the grafting density (σ) of PS ligands, (3) the size of Au NPs (R), and (4) the molecular weight of the BCP matrix (P). Morphological transitions between alternate-layered onions, seeded onions, and crusted onions are observed by carefully manipulating these variables. To account for these phenomena, we propose a modified swelling ratio (P/NSDPB) by considering grafted polymers in the semi-dilute polymer brush (SDPB) regime as the only chains available to interact with BCP matrices. This modified parameter successfully explains the structural transitions of the hybrid particles by including the effect of the chain conformation of the grafted polymers on the hybrid particle assembly. Furthermore, the overall Au@PS NP size (d) is considered as a complementary parameter to P/NSDPB for evaluating the BCP/Au@PS interactions, and together they provide a comprehensive understanding of the hybrid particle self-assembly.

Synthesis and Characterization of the New Cluster Complex {Mo3S4} with the Hemilabile Phosphine-Selenoether Ligand

The reaction of [Mo3S4(Tu)8(H2O)]Cl4·4H2O (Tu is thiourea) with (PhCH2CH2)2-PCH2CH2SeC5H11) (PSe) followed by purification on a chromatographic column packed with silica gel using a saturated solution of KPF6 in acetone as an eluent results in the formation of [Mo3S4Cl3(PSe)3]PF6 (I) in a yield of 44%. Compound I is characterized by X-ray diffraction analysis, 1H, 31P{1H}, and 77Se NMR spectroscopy, IR spectroscopy, UV-Vis spectroscopy, cyclic voltammetry, and electrospray ionization mass spectrometry. Several species differed in the coordination mode of three PSe ligands, which can bind to molybdenum via one (phosphorus) or two (phosphorus and selenium) donor atoms, are formed in a solution of compound I at room temperature. This behavior is not observed for the compounds similar in structure with PS ligands of an analogous type. Complex I demonstrates a higher catalytic activity than its analogue with the PS ligand in the reduction of nitrobenzene to aniline under the action of diphenylsilane.

Sulphated polysaccharides from seaweeds as potential entry inhibitors and vaccine adjuvants against SARS-CoV-2 RBD spike protein: a computational approach

The health pandemic (covid-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected, to date, over 233 million people and over 4.77 million deaths worldwide. Therefore, it is important to offer a wide understanding of the ability of potential antiviral biomolecules to combat this virus, which begins to develop new variants, potentially more transmissible and infectious. Sulphated polysaccharides (SPs) from seaweeds have been reported for their antiviral activity and their potential as vaccine adjuvants. However, their effect against SARS-CoV-2 remains very limited. In this study, seventeen ligands of SPs were screened for effective interaction with the domain (RBD) spike protein using a computational approach. The obtained results indicated that two PS ligands (Xylan sulphate and Heparin tetrasaccharide N-sulphated) effectively bind to the RBD protein and could efficiently inhibit viral entry. Overall, data support the potential importance of SPs against SARS-CoV-2 as entry inhibitors and vaccine adjuvants. Highlights Seventeen ligands of sulphated polysaccharides (SPs) were subjected to a molecular docking to assess their interaction with SARS-CoV-2 RBD spike protein; Two SP ligands showed an effective binding affinity to the RBD protein and could efficiently inhibit viral entry; One effective SP ligand (Xylan Sulphate) was predicted using ADMETox evaluation as good inhibitor; Effective candidates can have an importance against SARS-CoV-2 as entry inhibitors and vaccine adjuvants.

Trinuclear M3S4 cluster complexes with hemilabile phosphino-thioether ligands: Some experimental and theoretical aspects

Reactions of [W3S4(tu)8(H2O)]Cl4⋅2H2O (tu = thiourea) with (PhCH2CH2)2PCH2CH2SR (R = Ph (PS1) or n-pentyl (PS2), followed by chromatography on silica gel with a solution of KPF6 in acetone as eluent, result in [W3S4Cl3(PS1)3]PF6 ([1]PF6) and [W3S4Cl3(PS2)3]PF6 ([2]PF6) in moderate yields. Crystal structures of [1]PF6 and [2]PF6 were determined by X-ray single crystal analysis. All three phosphine-thioether molecules are bidentately coordinated to tungsten atoms in such a way that the phosphorus atoms are in the trans position to the capping µ3-S atom. The compounds were characterized by 1H, 31P{1H} NMR, and UV–vis spectroscopies and electrospray-ionization mass spectrometry. Unlike similar molybdenum complexes, interaction of [1]PF6 or [2]PF6 with Bu4NCl does not lead to the formation of neutral complexes [W3S4Cl4(PS)2(PS*)] with the monodentate coordination of one of the PS ligands. This indicates weaker hemilabile properties of phosphino-thioether ligands in the tungsten complexes. Consequently, both [1]PF6 and [2]PF6 exhibit significantly lower catalytic activity than the molybdenum analogues in the benchmark reaction of nitrobenzene reduction into aniline with Ph2SiH2. The DFT calculations were performed to determine the relative stability of possible isomers with the chelate, bridging and monodentate manner of coordination of the PS ligands to {M3S4} (M = Mo, W) clusters, taking (CH3)2PCH2CH2SCH3 as a model.

Precise Localization of Inorganic Nanoparticles in Block Copolymer Micellar Aggregates: From Center to Interface

Localization of inorganic nanoparticles (NPs) into polymer matrix plays a crucial role in determining the performance of the hybrid materials. Herein, we employed a simple, yet versatile hydrogen bonding directed supramolecular assembly (HBSA) strategy to control the localization of Au NPs from the center to the interface in polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) cylindrical micellar aggregates by tailoring the selectivity of polymer brushes on the surface of Au NPs. PS-b-P4VP(PDP)x comb–coil supramolecules were constructed by PS-b-P4VP and n-pentadecylphenol (PDP) via the hydrogen bonding between the pyridine of P4VP and the hydroxyl of PDP. PS-tethered Au NPs (PS-Au NPs) were selectively localized in the PS domain while a binary mixture of PS and P4VP-tethered Au NPs (PS/P4VP-Au NPs) were adsorbed to the interface between PS and P4VP(PDP)x domains presumably due to the redistribution of PS and P4VP ligands on the Au NPs surface, triggering the formation of amphiphilic surfactant-like NPs. Isolated cylindrical micellar aggregates with controlled localization of Au NPs were obtained by the selective disassembly of the supramolecules. Moreover, supramolecular block domain size, composition of the supramolecules, size of the Au NPs, and volume fraction of the Au NPs were carefully investigated to reveal their effects on the morphology of hybrid micellar aggregates and localization of NPs. These hybrid micellar aggregates with controlled localization and loading efficiency of Au NPs may extend the applications of the hybrid micellar aggregates and find more potential uses in optical/electronic devices, catalysis, and drug delivery system.

Assembly of polystyrene-coated gold nanoparticles at the air–water interface

Gold nanoparticles (NPs) coated with thiol-terminated polystyrene chains of varying molar mass were added to polystyrene-b-polymethylmethacrylate (PS-b-PMMA) block copolymer monolayers at the air–water interface. Composite films were transferred to solid substrates by the Langmuir–Blodgett technique. For most of the investigated systems, TEM micrographs and AFM images reveal the formation of 2D island-like aggregates of particles organized on a close-packed hexagonal lattice. This characteristic aggregate formation is lost when PS ligands are within the same length regime as the PS block from the copolymer. The results are compared with those obtained for analogous systems containing no copolymer where NPs are deposited on either a bare water surface or bare glass. Interparticle distance between NPs is found to depend on the surface on which they are deposited, the presence or not of the copolymer monolayer, and ligand length.

Nanoporous Bicontinuous Structures via Addition of Thermally-Stable Amphiphilic Nanoparticles within Block Copolymer Templates

Herein, we fabricated the bicontinuous structures from nanocomposites of poly(styrene-b-methyl methacrylate) (PS-b-PMMA) block copolymer and the shell-cross-linked, thermally stable gold nanoparticles (Au NPs). The surface property of Au NPs was controlled with ligands containing various compositions of PS and PMMA so that the resulting Au NPs were selective to PS or PMMA block or nonselective (i.e., neutral) to both blocks. The amphiphilic Au NPs were also prepared by coating the surface of Au NPs with equimolar mixtures of PS and PMMA selective ligands. Consequently, it was found that the morphological behaviors of thermally annealed nanocomposites containing amphiphilic Au NPs and PS-b-PMMA were dramatically different from the case of neutral Au NPs that were coated with nonselective ligands. With increasing the amount of amphiphilic Au NPs, a transition from lamellar to bicontinuous structures was observed, whereas the neutral Au NPs were aggregated within the PS-b-PMMA lamellae. Furthermore, the nanoporous bicontinuous thin films were fabricated on the silicon substrates and the morphological behaviors were quantitatively investigated by grazing-incidence small-angle X-ray scattering (GISAXS) analysis.

Tailoring Core−Shell Polymer-Coated Nanoparticles as Block Copolymer Surfactants

The effect of core−shell polymer-coated nanoparticles on block copolymer morphology is investigated systematically by controlling particle positioning within a block copolymer template. Our approach of varying the areal chain density (Σ) of short thiol terminated polystyrene (PS-SH) brushes on the particles where the molecular weight (Mn) of the PS ligands (2.5 kg/mol) is used to control the fraction of the particles adsorbed to the interface of PS-b-P2VP diblock copolymer domains (Mn = 196 kg/mol). The change in Σ from 2.38 to 0.49 chains/nm2 brings systematic control over the fraction of Au particles bound to the PS/P2VP interface (fi), this fraction ranging from 0 to 95%. Particles with Σ of 2.38 chains/nm2 (fi ∼ 0) were observed to localize within the PS domains and further produce a macroscopic particle aggregated phase separate from the PS-b-P2VP mesophase. In contrast, decreasing the Σ of PS chains provides for strong binding of Au nanoparticles to the PS/P2VP interfaces as a consequence of preferential wetting of one block of the copolymer (P2VP) to the Au substrate. Interestingly, the addition of low volume fractions (ϕP) of such nanoparticle surfactants (Σ < 1.1 chains/nm2) to lamellar diblock copolymers initially leads to a decrease in lamellar thickness, a consequence of decreasing interfacial tension, up to a critical value of ϕP beyond which the block copolymer adopts a bicontinuous morphology. The relationship between domain spacing and morphology of block copolymer with the level of nanoparticle surfactants will be discussed based on a strong-segregation model. In addition, the rational design of nanoparticle surfactants based on the nature and density of the grafted chains will be described.

Creating Surfactant Nanoparticles for Block Copolymer Composites through Surface Chemistry

A simple strategy to tailor the surface of nanoparticles for their specific adsorption to and localization at block copolymer interfaces was explored. Gold nanoparticles coated by a mixture of low molecular weight thiol end-functional polystyrene (PS-SH) (Mn = 1.5 and 3.4 kg/mol) and poly(2-vinylpyridine) homopolymers (P2VP-SH) (Mn = 1.5 and 3.0 kg/mol) were incorporated into a lamellar poly(styrene-b-2-vinylpyridine) diblock copolymer (PS-b-P2VP) (Mn = 196 kg/mol). A library of nanoparticles with varying PS and P2VP surface compositions (FPS) and high polymer ligand areal chain densities was synthesized. The location of the nanoparticles in the PS-b-P2VP block copolymer was determined by transmission electron microscopy. Sharp transitions in particle location from the PS domain to the PS/P2VP interface, and subsequently to the P2VP domain, were observed at FPS = 0.9 and 0.1, respectively. This extremely wide window of FPS values where the polymer-coated gold nanoparticles adsorb to the interface suggests a redistribution of PS and P2VP polymers on the Au surface, inducing the formation of amphiphilic nanoparticles at the PS/P2VP interface. In a second and synthetically more challenging approach, gold nanoparticles were covered with a thiol terminated random copolymer of styrene and 2-vinylpyridine synthesized by RAFT polymerization. Two different random copolymers were considered, where the molecular weight was fixed at 3.5 kg/mol and the relative incorporation of styrene and 2-vinylpyridine repeat units varied (FPS = 0.52 and 0.40). The areal chain density of these random copolymers on Au is unfortunately not high enough to preclude any contact between the P2VP block of the block copolymer and the Au surface. Interestingly, gold nanoparticles coated by the random copolymer with FPS = 0.4 were dispersed in the P2VP domain, while those with FPS = 0.52 were located at the interface. A simple calculation for the adsorption energy to the interface of the nanoparticles with different surface arrangements of PS and P2VP ligands supports evidence for the rearrangement of thiol terminated homopolymers. An upper limit estimate of the adsorption energy of nanoparticles uniformly coated with a random arrangement of PS and P2VP ligands where a 10% surface area was occupied by P2VP -mers or chains was approximately 1 kBT, which indicates that such nanoparticles are unlikely to be segregated along the interface, in contrast to the experimental results for nanoparticles with mixed ligand-coated surfaces.

Thermally Driven Assembly of Nanoparticles in Polymer Matrices

Thermally responsive bulk polymer films utilizing reversible Diels−Alder chemistry have been developed. Gold nanoparticles (AuNPs) were passivated with thiol-terminated poly(styrene)-b-poly(ethylene glycol) (PS-b-PEG) copolymer ligand, where the PS and PEG blocks are joined via a Diels−Alder (DA) linkage. The ligand-functionalized nanoparticles were dispersed within a microphase-separated PS-b-poly(methyl methacrylate) (PS-b-PMMA) block copolymer. Nanoparticle location was dictated by the compatibility of the external shell with the block copolymer matrix. As cast, the PEG shell compatibilized the nanoparticles with the PMMA domains. Subsequent thermal treatment caused the Diels−Alder linkages between the polymer blocks to dissociate, leaving the AuNPs functionalized by PS ligands. Immiscibility within the PMMA matrix caused AuNP migration to the PS domains. Migration of the Au nanoparticles was determined using morphological characterization via small-angle X-ray scattering (SAXS) and cross-sectional transmission electron microscopy (TEM).

Terminally Coordinated AsS and PS Ligands

The terminal AsS and PS complexes [(N(3)N)W(ES)] (N(3)N=N(CH(2)CH(2)NSiMe(3))(3); E=P (3), As (4)) were synthesised by reaction of [(N(3)N)W[triple chemical bond]As] and [(N(3)N)W[triple chemical bond]P], respectively, with cyclohexene sulfide. Both complexes present very short W--E and E--S bond lengths. The bonding was investigated by density functional theory (DFT) calculations using the fragment calculation method and natural bond orbital (NBO) analysis. According to the fragment analysis, in which the complexes were separated in an ES and a (N(3)N)W fragment, the bonding in complexes 3, 4 and [(N(3)N)W(SbS)] (5) is realised over a set of two sigma (1 sigma and 2 sigma) and two degenerate pi molecular orbitals (MOs) (1 pi and 2 pi). The 1 sigma MO is a bonding MO extended over the N(ax)-W-E-S core, whereas the 2 sigma MO is localised mainly on the E-S fragment. The 1 pi set is a E-S localised bonding molecular orbital, whereas the 2 pi set is in phase with respect to W-E but in antiphase with respect to E-S. Both methods indicate bond orders around two for both the E--S and the W--E bonds. The polarity of the complexes was examined by Hirshfeld charge analysis. This shows that complexes 3 and 4 are only slightly polarised, whereas 5 is moderately polarised toward the sulphur. As suggested by the computational results, the pi system in complexes 3-5 is best described by two three-centre four-electron bonds.

Metal thiophosphonates and related compounds: an emerging area of supramolecular coordination chemistry

Nine new compounds containing PS ligands of the types [P(OtBu)S3]2-, [ArP(StBu)S2]- and [ArP(OtBu)S2]- are reported (Ar = 4-anisyl). It is demonstrated that the topology of alkali metal ion and ligand composition influence the structure of supramolecular arrangements.

The CO/PC analogy in coordination chemistry and catalysis

This short account summarizes recent results obtained in the coordination chemistry of phosphinines and emphasizes their analogy with CO ligands. Reduced complexes can be easily assembled through the reaction of reduced 2,2′-biphosphinine dianions with transition metal fragments. Theoretical calculations were performed to establish the oxidation state of the metal in these complexes. Though many reduced complexes are available, phosphinines proved to be too sensitive toward nucleophiles to be used as efficient ligands in most catalytic processes. However, the high electrophilicity of the phosphorus atom can be exploited to synthesize phosphacylohexadienyl anions which exhibit a surprising coordination chemistry. When phosphino sulfide groups are incorporated as ancillary tridentate anionic SPS ligands can be easily produced. These ligands can bind different transition metal fragments such as M–X (M = group 10 metal, X = halogen), Rh–L (L = 2 electron donor ligand), Cu–X and Au–X (X = halogen). Palladium(II) complexes proved to be active catalyst in the Miyaura cross-coupling reaction. Bidentate anionic PS ligands were also synthesized following a similar approach. Their Pd(II) (allyl) derivatives showed a very good activity in the Suzuki catalyzed cross-coupling process that allows the synthesis of biphenyl derivatives through the reaction of phenylboronic acid with bromoarenes.

Ruthenium(II) carbonyl complexes containing tertiary phosphine chalcogenide ligands of the type Ph3PX; X=O, S, Se

The complexes [Ru(CO) 2 Cl 2 (Ph 3 PX)] and [Ru(CO) 2 Cl 2 (Ph 3 PX) 2 ] are produced on treatment of [Ru(CO) 2 Cl 2 ] n with 1:1 and 1:2 mol ratio of the ligands Ph 3 PX; X=O, S, Se, respectively. The molecular structure of [Ru(CO) 2 Cl 2 (Ph 3 PS) 2 ] was determined by single X-ray crystallography and Ru atom occupies the center of the slightly distorted octahedral geometry. The reactions of polymeric complex [Ru(CO) 2 Cl 2 ] n with triphenyl phosphine chalcogenide ligands Ph 3 PX; X=O( a ), S( b ), Se( c ) in 1:1 (Ru:L ratio) molar ratio gives five-coordinate complexes of the type [Ru(CO) 2 Cl 2 (Ph 3 PX)]( 1a – c ) while 1:2 (Ru:2L ratio) molar ratio produces six-coordinate [Ru(CO) 2 Cl 2 (Ph 3 PX) 2 ]( 2a – c ) complexes. The complexes 1a – c and 2a – c exhibit two equally intense ν (CO) bands in the range 2059–1989 and 2050–1980 cm −1 , respectively, indicating cis -disposition of the two terminal carbonyl groups. The values of ν (CO) frequencies irrespective of the complexes, in general, follow the order: Ph 3 PO > Ph 3 PS > Ph 3 PSe which may be ascribed in terms of “Soft–Hard” (Ru(II)–O) and “Soft–Soft” (Ru(II)–S/Se) interactions. The ν (PX) bands of the complexes observed in the range 1173–538 cm −1 are 19–41 cm −1 lower than those of the corresponding free ligands indicating the formation of Ru–X bonds. The molecular structure of the complex [Ru(CO) 2 Cl 2 (Ph 3 PS) 2 ] was determined by single X-ray crystallography. The crystal is monoclinic, space group Cc; a =11.4990 Å, b =17.3966 Å, c =18.4788 Å; α =90°, β =98.160°, γ =90°. In the molecule, the Ru(II) atom occupies the center of a slightly distorted octahedral geometry which consists of two trans -S atoms of two Ph 3 PS ligands, two cis -CO groups and two cis -chlorides. The complexes have also been characterized by elemental analysis, 1 H, 13 C and 31 P NMR spectroscopy.

Cp*Fe(η5-P5)] as a Useful Source for the Synthesis of Cobalt Complexes with “Naked” Pn Ligands

A rich diversity of CpRCo complexes with “naked” Pn ligands is obtained upon treatment of [Cp*Fe(η5-P5)] (1) with [CpRCo(CO)2], CpR = C5H4tBu, C5H3tBu2-1,3. Besides the “triple decker” (shown right) with a planar CoP4 middle deck, clusters with trigonal bipyramidal and cubanelike Co3P2, Co4P4, and FeCo2P5 skeletons have been synthesized. The hitherto unknown μ4-η5:η2:η2:η1-coordination mode of the cyclo-P5 ligand in the complex [{Cp*′FeP5}{Co3Cp3R(CO)2}] has been realised. The coordinative stabilization of PS and PSe ligands is described.

PS Ligands as Building Blocks of Chiral Dimetallatetrahedranes with a Common Vertex

PS Ligands as Building Blocks of Chiral Dimetallatetrahedranes with a Common Vertex