Copolymeric films obtained by electropolymerization of porphyrins and dipyridyl-spacers including Dawson-type polyoxometalates

Electropolymerization of Metallo-Octaethylporphyrins: A Study to Explore Their Sensing Capabilities

The electropolymerization of metallo-octaethylporphyrins (OEP) containing copper, zinc or nickel metal were performed using cyclic voltammetry at three different potential ranges. The electropolymerized porphyrins were characterized by UV-Vis and Raman spectroscopies and the Soret band (393-445 nm) and Raman bands were used to assess the degree of electropolymerization obtained. The application for an analytical use of the modified electrodes to determine phenobarbital in aqueous solution was evaluated. The electropolymerized CuOEP produced at potentials ranging from 0.0 to 2.2 V was the best performer with a limit of detection (LoD) of 10 mg L^-1 (43.07 µM), a linear range of 10-150 mg L^-1 (43.07 to 646 µM), an average precision of 4.3% (%RSD) and an average % recovery of 101.34%. These results indicate that the CuOEP-modified electrode is suitable for the analysis of phenobarbital in human samples, as the concentration range varies from 10 to 40 mg L^-1 (43.07 to 172.27 µM), typically found in antiepileptic treatments, to those at the toxic level (172-258 µM) or lethal levels (345-650 µM).

Polyoxometalates as chemically and structurally versatile components in self-assembled materials

Polyoxometalates (POMs) are anionic molecular metal oxides with expansive diversity in terms of their composition, structure, nuclearity and charge. Within this vast collection of compounds are dominant structural motifs (POM platforms), that are amenable to significant chemical tuning with minimal perturbation of the inorganic oxide molecular structure. Consequently, this enables the systematic investigation of these compounds as inorganic additives within materials whereby structure and charge can be tuned independently i.e. [PW12O40]3- vs. [SiW12O40]4- while also investigating the impact of varying the charge balancing cations on self-assembly. The rich surface chemistry of POMs also supports their functionalisation by organic components to yield so-called inorganic-organic hybrids which will be the key focus of this perspective. We will introduce the modifications possible for each POM platform, as well as discussing the range of nanoparticles, microparticles and surfaces that have been developed using both surfactant and polymer building blocks. We will also illustrate important examples of POM-hybrids alongside their potential utility in applications such as imaging, therapeutic delivery and energy storage.

Copolymers of bipyridinium and metal (Zn & Ni) porphyrin derivatives; theoretical insights and electrochemical activity towards CO2

This study reports the electropolymerization of novel keto functionalized octaethyl metal porphyrins (Zn²⁺ and Ni²⁺) in the presence of 4,4′-bipyridine (4,4′-bpy) as a bridging nucleophile. The polymer films were characterized by electrochemical, spectroscopic (UV-Vis, XPS, FT-IR and Raman spectroscopy) and imaging (AFM and SEM) techniques. The absorption and electronic spectra confirm the presence of both porphyrin and 4,4′-bipyridine units in the film. The surface morphology reveals homogeneous film deposition with average roughness values of approx. 8 nm. The theoretical studies performed offered insights into the interplay of different metal centres (Zn²⁺ and Ni²⁺) and the keto functionality of the porphyrin unit in the formation of copolymer films. The electrochemical interaction of polymer films with CO₂ suggests a reversible trap and release of CO₂ with low energy barriers for both the polymers.

Electropolymerization of keto functionalized porphyrins and 4,4′-bipyridine.

Hybrid polyoxometalates as post-functionalization platforms: from fundamentals to emerging applications

Polyoxometalates (POMs) represent an important group of metal-oxo nanoclusters, typically comprised of early transition metals in high oxidation states (mainly V, Mo and W). Many plenary POMs exhibit good pH, solvent, thermal and redox stability, which makes them attractive components for the design of covalently integrated hybrid organic-inorganic molecules, herein referred to as hybrid-POMs. Until now, thousands of organic hybrid-POMs have been reported; however, only a small fraction can be further functionalized using other organic molecules or metal cations. This emerging class of 'post-functionalizable' hybrid-POMs constitute a valuable modular platform that permits coupling of POM properties with different organic and metal cation functionalities, thereby expanding the key physicochemical properties that are relevant for application in (photo)catalysis, bioinorganic chemistry and materials science. The post-functionalizable hybrid-POM platforms offer an opportunity to covalently link multi-electron redox responsive POM cores with virtually any (bio)organic molecule or metal cation, generating a wide range of materials with tailored properties. Over the past few years, these materials have been showcased in the preparation of framework materials, functional surfaces, surfactants, homogeneous and heterogeneous catalysts and light harvesting materials, among others. This review article provides an overview on the state of the art in POM post-functionalization and highlights the key design and structural features that permit the discovery of new hybrid-POM platforms. In doing so, we aim to make the subject more comprehensible, both for chemists and for scientists with different materials science backgrounds interested in the applications of hybrid (POM) materials. The review article goes beyond the realms of polyoxometalate chemistry and encompasses emerging research domains such as reticular materials, surfactants, surface functionalization, light harvesting materials, non-linear optics, charge storing materials, and homogeneous acid-base catalysis among others.