Counterion Exchange Research Articles

Counterion-Tunable Thermosensitivity of Strong Polyelectrolyte Brushes.

In this work, poly(sodium styrene sulfonate) brushes have been employed as a precursor to prepare thermosensitive strong polyelectrolyte brushes (SPBs) through a counterion exchange strategy. The substitution of hydrophilic Na+ counterions by hydrophobic tetraalkylphosphonium counterions leads to a thermoresponsivity of the SPBs. The thermosensitive properties including hydration, stiffness, and surface water wettability of the SPBs can be modulated by the type of the tetraalkylphosphonium counterions. Nevertheless, the wet thickness of the SPBs with tetraalkylphosphonium counterions does not exhibit an obvious temperature dependency due to the high steric barrier in the crowded environment of SPBs generated by the large tetraalkylphosphonium counterions. The mixtures of small Na+ counterions and large tetraalkylphosphonium counterions are employed to realize the thermosensitive wet thickness without sacrificing other thermoresponsive properties of the SPBs because the mixed counterions can bring both a certain hydrophobicity and some free space to the brushes. This work opens up the opportunities available for the use of counterions to tune the thermosensitivity of SPBs.

Counterion‐Switched Reversibly Hydrophilic and Hydrophobic TiO2‐Incorporated Layer‐By‐Layer Self‐Assembled Membrane for Nanofiltration

AbstractThe manipulation of surface wettability has been regarded as an efficient strategy to improve the membrane performances. Herein, the counterion‐switched reversibly hydrophilic and hydrophobic surface of TiO2‐loaded polyelectrolyte membrane are prepared by layer‐by‐layer assembly of poly(sodium 4‐styrene sulfonate) (PSS) and poly(diallydimethyl‐ammoniumchloride (PDDA) containing TiO2@PDDA nanoparticles (NPs) on the hydrolyzed polyacrylonitrile (PAN) substrate membrane. The obtained polyelectrolyte multilayer (PEM) membranes [PEM‐TiO2]4.5+X− (X− = Cl−, PFO− [perfluorooctanoate] etc.) show different hydrophilicity and hydrophobicity with various counterions. The integration of TiO2 NPs obviously improves the wettability and nanofiltration (NF) performance of PEM membrane for (non)aqueous system of dyes (crystal violet, eriochrome black T) with a high recyclability. The highly hydrophilic [PEM‐TiO2]4.5+Cl− (water contact angle [WCA]: 13.2 ± 1.8°) and hydrophobic [PEM‐TiO2]4.5+PFO− (WCA: 115.4 ± 2.3°) can be reversibly switched via counterion exchange between Cl− and PFO−, verifying the surface with a reversible hydrophilic–hydrophobic transformation. For such membranes, the morphology, wettability, and NF performance rely on the loading of TiO2@PDDA NPs and surface counterion. Meanwhile, the motion and interaction of water or ethanol in the hydrophilic or hydrophobic membrane are revealed by low‐field nuclear magnetic resonance. This work provides a facile and rapid approach to fabricate smart and tunable wetting surface for potential utilization in (non)aqueous NF separation.

Palladium catalyzed/counter ion tuned selective methylation of o-carboranes

The palladium catalyzed/counter ion tuned selective methylation of 9-amide-o-carboranes on B(4) and B(12) has been developed, and a series of o-carborane derivatives decorated with various groups have been synthesized with moderate yields. The in situ formed palladium species via counter ion exchange was proposed for the tunable B–H activation.

Tumor-Targeting NIRF NanoGUMBOS with Cyclodextrin-Enhanced Chemo/Photothermal Antitumor Activities.

The near-infrared fluorescent (NIRF) dye, IR780, is recognized as a promising theranostic agent and has been widely investigated for imaging, chemotherapeutic, and phototherapeutic applications. However, its poor photostability and nonselective toxicities toward both cancer and normal cells limit its biological applications. Herein, we introduce the use of GUMBOS (a group of uniform materials based on organic salts) developed through counter-anion exchange with IR780 and subsequent nanomaterials (nanoGUMBOS) formed by complexation with cyclodextrin (CD) for enhanced chemo/photothermal therapy. Such CD-based nanoGUMBOS display improved aqueous stability, photostability, and photothermal effects relative to traditional IR780. The examination of in vitro cytotoxicity reveals that CD-based nanoGUMBOS are selectively toxic toward cancer cells and exhibit synergistically enhanced cytotoxicity toward cancer cells upon NIR laser irradiation. Additionally, in vivo NIRF imaging demonstrated selective accumulation of these nanoGUMBOS within the tumor site, indicating tumor-targeting properties. Further in vivo therapeutic study of these CD-based nanoGUMBOS suggests excellent chemo/photothermal antitumor effects. Using these studies, we herein demonstrate a promising strategy, via conversion of IR780 into nanoGUMBOS, that can be used for improved theranostic cancer treatment.

Counterion Exchange in Peptide-Complexed Core-Shell Microgels.

The complexation of polyvalent macroions with oppositely charged polyelectrolyte microgels can lead to core-shell structures. The shell is believed to be highly deswollen with a high concentration of counter-macroions. The core is believed to be relatively free of macroions but under a uniform compressive stress due to the deswollen shell. We use cryo-scanning electron microscopy (SEM) with X-ray microanalysis to confirm this understanding. We study poly(acrylic acid) (PAA) microgels which form a core-shell structure when complexed with a small cationic antimicrobial peptide (L5). We follow the spatial distribution of polymer, water, Na counterions, and peptide based on the characteristic X-ray intensities of C, O, Na, and N, respectively. Frozen-hydrated microgel suspensions include buffers of known composition from which calibration curves can be generated and used to quantify both the microgel water and sodium concentrations, the latter with a minimum quantifiable concentration less than 0.048 M. We find that as-synthesized PAA microgels are enriched in Na relative to the surrounding buffer as anticipated from established ideas of counterion shielding of electrostatic charge. The shell in L5-complexed microgels is depleted in Na and enriched in peptide and contains relatively little water. Our measurements furthermore show that shell/core interface is diffuse over a length scale of a few micrometers. Within the limits of detection, the core Na concentration is the same as that in as-synthesized microgels, and the core is free of peptide. The core has a slightly lower water concentration than as-synthesized controls, consistent with the hypothesis that the core is under compression from the shell.

Zinc transporter 10 (ZnT10)-dependent extrusion of cellular Mn2+ is driven by an active Ca2+-coupled exchange

Manganese (Mn2+) is extruded from the cell by the zinc transporter 10 (ZnT10). Loss of ZnT10 expression caused by autosomal mutations in the ZnT10 gene leads to hypermanganesemia in multiple organs. Here, combining fluorescent monitoring of cation influx in HEK293-T cells expressing human ZnT10 with molecular modeling of ZnT10 cation selectivity, we show that ZnT10 is exploiting the transmembrane Ca2+ inward gradient for active cellular exchange of Mn2+ In analyzing ZnT10 activity we used the ability of Fura-2 to spectrally distinguish between Mn2+ and Ca2+ fluxes. We found that (a) application of Mn2+-containing Ca2+-free solution to ZnT10-expressing cells triggers an influx of Mn2+, (b) reintroduction of Ca2+ leads to cellular Mn2+ extrusion against an inward Mn2+ gradient, and (c) the cellular transport of Mn2+ by ZnT10 is coupled to a reciprocal movement of Ca2+ Remarkably, replacing a single asparagine residue in ZnT10 (Asp-43) with threonine (ZnT10 N43T) converted the Mn2+/Ca2+ exchange to an uncoupled channel mode, permeable to both Ca2+ and Mn2+ The findings in our study identify the first ion transporter that uses the Ca2+ gradient for active counter-ion exchange. They highlight a remarkable versatility in metal selectivity and mode of transport controlled by the tetrahedral metal transport site of ZnT proteins.

Thermoelectric Performance of n‐Type Poly(Ni‐tetrathiooxalate) as a Counterpart to Poly(Ni‐ethenetetrathiolate): NiTTO versus NiETT

AbstractThe synthesis of the metal‐coordination polymer poly(nickel tetrathiooxalate) (NiTTO) is presented, which represents an alternative route to n‐type thermoelectric materials similar in nature to nickel ethenetetrathiolate (NiETT) polymers. The TTO monomer is synthesized through an electrochemical reduction of carbon disulfide, followed by coordination polymerization with a nickel(II) salt to yield a coordination complex polymer with a neutral repeat unit. An alkali metal counterion exchange and polymerization optimization are performed, and a thermoelectric power factor of 6 µW m−1 K−2 (electrical conductivity of over 10 S cm−1) is achieved for NiTTO composite films in a polyvinylidene fluoride (PVDF) matrix. This is significantly higher than other reported n‐type polymers (and to within a factor of two of NiETT) and demonstrates the potential of NiTTO as a new thermoelectric material. Elemental analysis indicates a nearly neutral backbone structure in NiTTO with minimal charge balancing alkali ions, indicating that these polymers are more oxidized than NiETTs. X‐ray photoelectron spectroscopy reveals a different coordination environment for NiTTO compared to NiETTs with the same alkali counterion, indicating that—despite their structural similarity in theory—these two materials are indeed different.

Self-assembly of polyhedral oligomeric silsesquioxane structures through ion exchange

In this study, we synthesized 3-chloroammoniumpropyl polyhedral oligomeric silsesquioxanes (CAP-POSS) by acid hydrolysis and condensation. Partial ion exchange resulted in the formation of supramolecular structures through electrostatic interactions. The interactions between POSS macroions were led by multiple hydrogen bonds that form supramolecular structures. After ion exchange, the structures of the CAP-POSS reduce the symmetry by the exchange of counterions and associate to form rigid transparent films at room temperature. The amount of chloride modulated the size and structure of macroions aggregates in the supramolecular films. Regardless of the amount of chloride removed, the films were formed of mass-fractal like structures with sizes ranging from 80 to 28 nm. The surface energy was proportional to the free amine content, and UV–vis was a light transmission characteristic. Therefore, the use of partial ion exchange represents an alternative to design of supramolecular POSS structures with properties tunable through multiple hydrogen bonds.

Nanotubular polypyrrole: Reversibility of protonation/deprotonation cycles and long-term stability

An alteration of electrical conductivity of the conducting polymers from a conducting to a non-conducting form and vice versa is a feature of the high importance. Here, the changes in conductivity of the polypyrrole nanotubes (PPy-NT) associated with a deprotonation/reprotonation in alkaline (various concentrations of ammonium or sodium hydroxide) or acidic (1 M hydrochloric or hydrobromic acid) solutions are presented. All experiments were followed by energy dispersive X-ray spectroscopy (EDX) elemental analyses and van der Pauw conductivity measurements. Extensive measurements of conductivity of samples during 2-years' timespan have also been made in order to determine the kinetics of natural ageing of the deprotonated/reprotonated PPy-NT. EDX measurements have allowed for a deeper insight into the process of the deprotonation/reprotonation of PPy-NT, which is generally characterized by the exchange of counter-ions and by the increase in the oxygen content. Correlations among conductivities of original, deprotonated and reprotonated samples revealed the universal behaviour, which can be used for the precise prediction of the ability of PPy-NT to be reprotonated by acids. Kinetics of the degradation of PPy-NT by natural ageing is faster for deprotonated sample and, on the contrary, the reprotonation by acids had a stabilizing effect.

A Robust Salty Water Adhesive by Counterion Exchange Induced Coacervate.

Counterion exchange of charged macromolecules has comprehensive implications in biological and synthetic systems such as protein function, biosignaling, ion conducting, and separation, but the correlation between the dynamic ion exchange, polyelectrolyte phase separation, and functionality remains elusive. Here, counterion exchange is exploited as a means to facilitate liquid-liquid phase separation and coacervates featuring higher stability and versatility compared with conventional complex coacervate. Self-coacervation of a cationic polyelectrolyte (polyamidoamine-epichlorohydrin, PAE-Cl) occurs in broader conditions when its original counter anion (Cl- ) is exchanged by bis(trifluoromethane-sulphonyl)imide anion (TFSI- ), as a result of TFSI- counter anions association instead of polyelectrolyte complexation. This coacervate is catechol-free, easy to prepare, and highlights robust wet adhesion strength on diverse submerged surfaces in salty water (pH = 3-11), as demonstrated by its versatile capability of in situ underwater gluing and repairing without any pre-immersive drying.

Base/Cryptand/Metal‐Free Automated Nucleophilic Radiofluorination of [18F]FDOPA from Iodonium Salts: Importance of Hydrogen Carbonate Counterion

As evidenced by the number of publications and patents published in the last years, the radiosynthesis of 6‐[18F]fluoro‐3,4‐dihydroxy‐L‐phenylalanine ([18F]FDOPA) using the nucleophilic [18F]F‐ process remains currently a challenge for the radiochemists scientific community even if promising methods for the radiofluorination of electron‐rich aromatic structures were recently developed from arylboronate, arylstannane or iodonium salt precursors. In such context, based on the use of an iodonium triflate salt precursor, we optimized a fast and efficient radiofluorination route fully automated and free from any base, cryptand or metal catalyst for the radiosynthesis of [18F]FDOPA. Using this method, this clinically relevant radiotracer was produced in 64 min, 27–38 % RCY d.c. (n = 5), >99 % RCP, >99 % ee., and high Am 170–230 GBq/µmol. In addition, this optimization study clearly highlighted the important role of a triflate‐hydrogen carbonate counterion exchange during the radiolabeling process to achieve high fluorine‐18 incorporation yields.

Nano-ion-exchangers - a new class of reactive materials

Nano-sized particles of functional polymers i.e. nano-ion-exchangers (NIEX), are unusual objects
 which simultaneously behave as the hyper-charged ions and the solid ion exchangers. Due to similar charges, they form very stable colloidal systems. This paper is devoted to theoretical and practical study of the proper- ties of nano-exchangers, methods for their preparation, the technique of experiments being practically un- known, and the opportunities for their application.
 The results of dynamic experiments are given for sorption of nano-exchangers and the ions of back- ground solutions on the beds of macro-particles of usual cationic and anionic resins. It is shown how to ob- tain the NIEX hydrosols with the desired ionic composition, and the concept of the standard state hydrosol is defined. The possibility for solid-phase exchange of counter ions between contacting particles of the same polarity is demonstrated.
 The possibilities and advantages of using nano-ion-exchangers in chemical analysis are demonstrat- ed by different examples: preparation of separating phases for ion chromatography, application as modifier in capillary electrophoresis and using in photo-luminescence. The prospects of nano-ion-exchangers for drug delivery are also shown.

Surface-hydrophobized TEMPO-nanocellulose/rubber composite films prepared in heterogeneous and homogeneous systems

A surface-carboxylated nanocellulose was prepared from wood cellulose by catalytic oxidation with 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO). The fibrous TEMPO-oxidized cellulose with sodium carboxylate groups (TOC-Na) was surface-hydrophobized by counterion exchange with tetra-n-butylammonium [TOC-N(n-Bu)4]. This fibrous TOC-N(n-Bu)4 was mechanically disintegrated in water and N,N-dimethylformamide (DMF) to prepare dispersions of TEMPO-oxidized cellulose nanofibrils (TOCNs) with tetra-n-butylammonium counterions, i.e., TOCN-N(n-Bu)4/water and TOCN-N(n-Bu)4/DMF. TOCN-N(n-Bu)4/rubber composite films were prepared by mixing TOCN-N(n-Bu)4 and hydrogenated acrylonitrile–butadiene rubber (H-NBR), used as a polymer matrix, in heterogeneous and homogeneous systems with water and DMF, respectively, followed by casting and drying. The TOCN-N(n-Bu)4/H-NBR composite films prepared in the heterogeneous and homogeneous systems both had a high Young’s modulus of ~ 45 MPa and low coefficients of thermal expansion of ~ 20 ppm/K at a TOCN/H-NBR ratio of 5/100 (w/w). In contrast, the tensile strengths and strain-to-failure values of the composite films prepared using the two systems clearly differed. These different properties are probably caused by differences between the TOCN distributions in the H-NBR matrix and between the H-NBR matrix structures in the two systems. The composite films prepared in the homogeneous system with DMF as the medium are likely to have a more homogeneous distribution of TOCN elements in a homogeneous H-NBR polymer matrix, resulting in a higher tensile strength and work-of-fracture at TOCN/H-NBR = 5/100 (w/w) compared with those of the films prepared in the heterogeneous system with water.

Preparation of Al-magadiite material, copper ions exchange and effect of counter-ions: antibacterial and antifungal applications

In this work, the Al-magadiite is synthesized by the hydrothermal method. It is then used to prepare three copper exchanged materials using copper nitrate, copper chloride, and copper sulfate salts. The materials obtained were characterized and applied as antibacterial and antifungal agents against pathogen strains. The characterization methods showed the presence of four coordinated aluminum atoms in the magadiite framework. The presence of aluminum leads to the total exchange of interlayer sodium cations. Otherwise, the copper exchange rate is influenced by the nature of the counter-ion used. Indeed, the exchanged rate increased in the sense of copper nitrate > copper chloride > copper sulfate. The chemical analysis shows that the ion exchange of Al-magadiite with copper salts is accompanied with dehydration of Cu-exchanged materials. This result was confirmed by XRD diffraction, chemical analysis, and FTIR spectroscopy. This dehydration depends on the nature of the counter ion increase also in the sense of copper nitrate > copper chloride > copper sulfate. Tested as antibacterial and antifungal materials against pathogens strains, all the copper exchanged materials exhibited a good antibacterial activity against Gram-positive bacteria which increased with increasing the copper content of a sample. The best activity was observed in the exchanged sample prepared from copper nitrate. However, a low or no activity is observed against Gram-negative bacteria.

Cyclooctadiene iridium complexes [Cp*Ir(COD)X]+ (X = Cl, Br, I): Synthesis and application for oxidative coupling of benzoic acid with alkynes

The cyclooctadiene iridium complexes [Cp*Ir(COD)X]PF6 ([1a−c]PF6; X = Cl, Br, I) were synthesized by reactions of Cp*Ir(COD) with halogens followed by a counterion exchange. The cyclooctadiene in these complexes is a thermally labile ligand. Complex [1b]PF6 reacts with trimethylphosphite to give [Cp*Ir{P(OMe)3}2Br]PF6 ([2]PF6) as a result of the cyclooctadiene replacement. The refluxing of [1b]PF6 in 1,2-dichloroethane affords the dimeric iodide [Cp*IrI2]2. The structures of [1b]PF6, [2]PF6 and [Cp*IrI2]2 were determined by X-ray diffraction. The Ir–COD bonding in [1a−c]+ and the related non-methylated complexes was analyzed by energy decomposition analysis. In the presence of silver salts, complexes [1a−c]PF6 (at 2.0 mol % loading) catalyze the oxidative coupling of benzoic acid with 1-phenyl-1-propyne in methanol at 60 °C to selectively give 4-methyl-3-phenylisocoumarin (3) or with diphenylacetylene in o-xylene at 160 °C to afford 1,2,3,4-tetraphenylnaphthalene (4).

Densely Charged Dodecacationic [3]- and Tetracosacationic Radial [5]Catenanes

Summary Here, we report the efficient syntheses of a dodecacationic [3]catenane, which consists of three mechanically interlocked 4+ charged rings despite their mutual Coulombic repulsion, and a tetracosacationic radial [5]catenane, which consists of four 4+ charged rings mechanically interlocked around an 8+ charged ring and bears up to 24 positive charges in its co-constitution. The solid-state structures, determined by single-crystal X-ray crystallography, show that the two mechanical bonds in the [3]catenane result in the nano-confinement of 12 positive charges within a volume of less than 1.65 nm3, corresponding to 7.3 positive charges per nm3, whereas the radial [5]catenane has a charge density of 6.0 positive charges per nm3 and a molecular length of up to 3.7 nm. The template-directed strategy for constructing mechanically interlocked molecules, consisting of multiply charged rings, represents a departure in chemistry tantamount to producing a blueprint for exploring a novel class of organic molecules that boast large numbers and high densities of like charges.

Study of Gelation for Biodegradable Polyelectrolytes By a Counter Ion Exchange Approach

Cationic polymers are promising as a new class of antimicrobials to combat a threat of emerging drug-resistant superbugs because multiple positive charges are effective in electrostatic interaction with negatively charged bacterial cell membranes, which leads to membrane disruption.1) Since this mechanism is fundamentally different from those of most conventional antibiotics that target inhibition of an intracellular function of bacteria, these antimicrobial polymers are believed not to contribute to development of drug resistance. Originating from the first report by Nederberg et al.,2) a series of biodegradable antimicrobial polycarbonates have been developed, and biodegradability and bioabsorbability have been recognized important for antimicrobials that injection into the body is assumed. We also have recently developed cationic antimicrobial polycarbonates tagging primary ammonium salts and a hydrophobic moiety at the side chains. These polymers exhibit antimicrobial activity and biocompatibility tuned by sequence, composition, and structure of hydrophobic comonomer units. Moreover, microbial colonization and biofilm formation on biomedical implants and devices are now acknowledged as a more severe threat and cause financial challenges for patients. Bacterial biofilm comprising complex exopolysaccharides matrix is difficult to destroy and thus serves as barriers against antibiotics. Antimicrobial hydrogels are envisioned to be an effective weapon to counter the biofilm problem.3) Biodegradable antimicrobial hydrogels are the current focus of our research because they are expected to be used for both inside and outside of the body, e.g., wound dressings for burn treatment and surface treatment of long-term implants such as catheters. In this study, we report a simple yet effective approach to generating charged biodegradable hydrogels using a counter anion exchange approach. By using di- or tri-carboxylic acids as a counter anion for a cationic ammonium group as well as a cross-linker, a cationic polymer network may be formed. Preliminary, we have already been successful to switch a counter carboxylate of the cationic polycarbonate. To form hydrogels, physical cross-linking points and balance of (de)hydration should be rationally controlled. Thus, we explore several combinations for cationic copolycarbonates with different compositions and hydrophobic side chains and di- and tri-carboxylic acids as shown in Figure 1. In addition, a chemically crosslinked cationic polycarbonate is examined for comparison. 1) Palermo, K. Kuroda, Appl. Microbial. Biotechnol. 2010, 87, 1605-1615. 2) Nederberg et al., Nature Chem. 2011, 3, 409-414. 3) Li et al., Angew. Chem. Int. Ed., 2013, 52, 674-678. Figure 1

Thermodynamics of Counterion Release Is Critical for Anion Exchange Membrane Conductivity.

As the field of anion exchange membranes (AEMs) employs an increasing variety of cations, a critical understanding of cation properties must be obtained, especially as they relate to membrane ion conductivity. Here, to elucidate such properties, metal cation-based AEMs, featuring bis(norbornene) nickel, ruthenium, or cobalt complexes, were synthesized and characterized. In addition, isothermal titration calorimetry (ITC) was used to probe counterion exchange thermodynamics in order to understand previously reported differences in conductivity. The ion conductivity data reported here further demonstrated that nickel-complex cations had higher conductivity as compared to their ruthenium and cobalt counterparts. Surprisingly, bulk hydration number, ion concentration, ion exchange capacity, and activation energy were not sufficient to explain differences in conductivity, so the thermodynamics of metal cation-counterion association were explored using ITC. Specifically, for the nickel cation as compared to the other two metal-based cations, a larger thermodynamic driving force for chloride counterion release was observed, shown through a smaller Δ Htot for counterion exchange, which indicated weaker cation-counterion association. The use of ITC to study cation-counterion association was further exemplified by characterizing more traditional AEM cations, such as quaternary ammoniums and an imidazolium cation, which demonstrated small variances in their enthalpic response, but an overall Δ Htot similar to that of the nickel-based cation. The cation hydration, rather than its hydration shell or the bulk hydration of the membrane, likely played the key role in determining the strength of the initial cation-counterion pair. This report identifies for the first time how ITC can be used to experimentally determine thermodynamic quantities that are key parameters for understanding and predicting conductivity in AEMs.

In-situ synthesis of platinum nanoclusters in polyelectrolyte multilayer films

A simple approach is presented for in-situ synthesis of Pt nanoclusters in a polymeric thin film. Polyelectrolyte multilayer (PEM) films assembled from poly(diallyldimethylammonium chloride) and poly(sodium styrenesulfonate) were used as supports and templates, into which precursor ions were introduced via counterion exchange, which were then reduced in situ to yield Pt nanoclusters embedded in the PEM films. The ion-exchange and reduction processes were monitored by UV–vis absorption spectroscopy, and the morphology of the nanoclusters was observed by high resolution transmission electron microscopy, showing the Pt nanoclusters were uniformly dispersed in PEMs and had a narrow size distribution. The effects of salt concentration, reduction time and temperature on the size of the nanoclusters were investigated. The method provides a facile and convenient approach to the synthesis of metal nanoclusters in polymer thin films for application in various fields.

Photovoltaic properties of supramolecular assemblies obtained by incorporation of Preysler's type polyoxometalate in a polycationic copolymer of porphyrin

Poly-zinc-octaethylporphyrin/P5W30 films have been obtained through incorporation of Preyssler-type polyoxometalate ions, namely [NaP5W30O110]14- (P5W30) into zinc octaethylporphyrin/viologen-based polymers (poly-ZnOEP) films. The latter has been achieved through a metathesis reaction involving exchange of the initial counter ions (PF6−) of the positively charged poly-ZnOEP by P5W30. The investigated polymers involve ZnOEP units covalently linked either through a dicationic mono-viologen or through a tetracationic bis-viologen spacer. These copolymers have been characterized by UV/Vis absorption spectroscopy, X-ray photoelectron spectroscopy, electrochemistry, AFM and by electrochemical impedance spectroscopy. Formation of the polymers through electropolymerization of viologen and porphyrin building blocks has also been monitored by EQCM. QCM measurements have been carried out to study the exchange of PF6− by [NaP5W30O110]14−. Finally, the photovoltaic performances of these polymers have been assessed by photocurrent transient measurements carried out under visible illumination.