Photocatalytic recovery of metals by Lindqvist-type polyoxometalate–porphyrin copolymer

Hybrid polyoxometalate–porphyrin copolymeric films can be obtained by the electro-oxidation of 5,15-ditolyl porphyrin (H$_{\mathbf{2}}$T$_{\mathbf{2}}$P) and zinc-$\beta$-octaethylporphyrin (ZnOEP) in the presence of the Lindqvist-type polyoxovanadates \mathrm{TBA}_{2}[\mathrm{V}_{6}\mathrm{O}_{13} \lbrace (\mathrm{OCH}_{2})_{3}\mathrm{CNHCO} (4\mbox {-}\mathrm{C}_{5}\mathrm{H}_{4}\mathrm{N})\rbrace _{2}] (Py-V$_{\mathbf{6}}$O$_{\mathbf{13}}$-Py). The photocatalytic properties of these films have been studied for the reduction of silver and platinum ions. In these hybrid materials, porphyrins can be excited by visible light and then play the role of photosensitizers able to give electrons to the polyoxovanadates catalysts

Photocatalytic recovery of metals by Lindqvist-type polyoxometalate–porphyrin copolymer

Hybrid polyoxometalate–porphyrin copolymeric films can be obtained by the electro-oxidation of 5,15-ditolyl porphyrin (H$_{\mathbf{2}}$T$_{\mathbf{2}}$P) and zinc-$\beta$-octaethylporphyrin (ZnOEP) in the presence of the Lindqvist-type polyoxovanadates \mathrm{TBA}_{2}[\mathrm{V}_{6}\mathrm{O}_{13} \lbrace (\mathrm{OCH}_{2})_{3}\mathrm{CNHCO} (4\mbox {-}\mathrm{C}_{5}\mathrm{H}_{4}\mathrm{N})\rbrace _{2}] (Py-V$_{\mathbf{6}}$O$_{\mathbf{13}}$-Py). The photocatalytic properties of these films have been studied for the reduction of silver and platinum ions. In these hybrid materials, porphyrins can be excited by visible light and then play the role of photosensitizers able to give electrons to the polyoxovanadates catalysts

Oxidation of Porphyrins in the Presence of Nucleophiles: From the Synthesis of Multisubstituted Porphyrins to the Electropolymerization of the Macrocycles

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Electrochemical properties of the [SiW 10 O 36 (M 2 O 2 E 2 )] 6− polyoxometalate series (M = Mo( v ) or W( v ); E = S or O)

International audienceElectronic Supplementary Information (ESI) available: FT-IR spectra of the compounds used in this study (Figure S1); Additional electrochemical data (Figure S2-S6), additional UV-Vis-NIR spectroelectrochemistry experiments (Figure S7-S12); effect of addition of an excess of Br2 on the electronic spectra of {SiW10-Mo2O2S2} in DMF (Figure S13); 29 Si NMR spectra of {SiW10-Mo2O2S2} in DMF/CH3CN mixtures before and after addition of one equivalent of Br2 (Figure S14). See This paper deals with the electrochemical studies performed in DMF on three iso-structural and iso-electronic compounds of general formula γ−[SiW10O36(M2O2E2)] 6-, which differ either by the nature of the metallic centers (M = Mo(V) or W(V)) or by the nature of the bridges between Mo(V) atoms (E = O 2-or S 2-). Interestingly, cyclic voltammetry experiments performed in dry DMF reveal electrochemical processes both in oxidation and in reduction modes. The nature of these processes are studied and elucidated by various electrochemical techniques such as coulometry, rotating disk electrodes, spectro-electrochemistry (IR and UV-Vis), NMR and DFT calculations

Paramagnetic Molecular Grippers: The Elements of Six-State Redox Switches

The development of semiquinone-based resorcin[4]arene cavitands expands the toolbox of switchable molecular grippers by introducing the first paramagnetic representatives. The semiquinone (SQ) states were generated electrochemically, chemically, and photochemically. We analyzed their electronic, conformational, and binding properties by cyclic voltammetry, ultraviolet/visible (UV/vis) spectroelectrochemistry, electron paramagnetic resonance (EPR) and transient absorption spectroscopy, in conjunction with density functional theory (DFT) calculations. The utility of UV/vis spectroelectrochemistry and EPR spectroscopy in evaluating the conformational features of resorcin[4]arene cavitands is demonstrated. Guest binding properties were found to be enhanced in the SQ state as compared to the quinone (Q) or the hydroquinone (HQ) states of the cavitands. Thus, these paramagnetic SQ intermediates open the way to six-state redox switches provided by two conformations (open and closed) in three redox states (Q, SQ, and HQ) possessing distinct binding ability. The switchable magnetic properties of these molecular grippers and their responsiveness to electrical stimuli has the potential for development of efficient molecular devices

Synthèse et applications d hybrides de porphyrine-POM pour la dépollution de l'eau par photocatalyse et production d'énergie solaire

ØThe dissertation is presented on 252 content pages which has been framed in five chapters and two annexures while the title page opens into a list of abbreviations followed by a foreword on the work. The core theme of the research work is to validate the extended photocatalytic properties of porphyrin-POM materials in evolving from UV to visible light range of solar spectrum. Which describing additional modes for synthesis of hybrid materials (i) electrostatic multilayer s comprising of Dawson , sandwich Dawson type and preyssler,s POM in combination with free base tetracationic porphyrin [H TPhN(Me) P ] (ii) an easy method of synthesis of two dimers with a pyridinium spacer (abbreviated 4-H Zn and 3-H Zn) (iii) Langmuir Schafer approach for hybrid monolayer. The prepared photoactive thin layers have been characterized by UV-visible spectroscopy and fluorescence spectroscopy for optical properties. Cyclic voltammetry for electrochemistry and ionic permeability studies. Atomic force microscopy (AFM) for surface morphology and its role in physical mechanism of reduction process and shape of nanostructures obtained. Transmission electron microscopy (TEM) has been used to interpret size and shape of dendritic silver nanoparticles obtained as photoreduction product. Although ,the ultimate goal is the photoreduction of heavy metals (Cr(VI), Hg(II), Cd(II), Pb(II) ), reduction of a simpler system like Ag ion has been chosen as a model system due to single electron simpler oxidation reduction process. A novel application of photocurrent generation from these hybrid films has been demonstrated in the fifth chapter of the manuscript as an initial studies which has enhanced the significance of all previously fabricated systems upto by many folds .The foresaid development of photovoltaic application has paved the way for future studies to enhance the photocurrent yield further by tuning the electron donor-acceptor system. Both components porphyrin and POM can be tuned with different axial substituent s and stereo chemical properties to achieve maximum yield of solar energy as well as diversified metal nanostructure for nanoelectronics, e.g. silver dendrites for sensor applications. At the end of the manuscript, three appendices describe successively the experimental techniques used to carry out this work, the Job method used to determine the stoichiometry and formation constants of complex electrostatic and coordination, and then finally the origin or Protocols for the synthesis of various compounds used.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Electrosynthèse de films hybrides photoactifs polyoxométallate-porphyrine

Les polyoxométallates (POMs) sont des analogues moléculaires d oxydes métalliques ayant une chimie photorédox particulièrement riche avec des applications dans des domaines aussi variés que la synthèse organique, l environnement, ou l énergie. En général, les POMs n absorbent principalement que la lumière UV, ce qui limite fortement leur emploi sous irradiation solaire. Leur photosensibilisation par des chromophores absorbant la lumière visible s est révélée être une approche efficace pour palier cette limitation. En utilisant des méthodes rapportées de fonctionnalisation du tungstovanadate à structure de Dawson [P2V3W15O62]9-, nous avons préparé une série d hybrides POM-dipyridyle avec des espaceurs organiques conjugués de tailles et d architectures différentes. L oxydation de l octaéthylporphyrine de zinc par voie électrochimique en présence de ces POM-dipyridyle ou d espaceurs dipyridyles non greffés sur des POMs conduit à la formation de films uniformes déposés sur des électrodes transparentes d ITO. La taille et l architecture des espaceurs dipyridyles a un effet important sur leur réactivité et donc sur l épaisseur maximale des films. L épaisseur peut également être finement contrôlée en jouant sur les paramètres expérimentaux de déposition. La capacité de ces films de porphyrines avec et sans POMs à générer du photocourant sous irradiation visible a été étudiée. Nous avons observé que l intensité des photocourants dépendait à nouveau de l architecture de l espaceur organique, mais également de l épaisseur des films.Polyoxometalates (POMs) are metal oxides molecular analogues having interesting photoredox chemistry with synthetic, environmental and energetic applications. However, UV light is required for POM activation which strongly limits their use under a more sustainable solar visible light irradiation. The photosensitization of POMs with visible light antenna molecules has proved to be an efficient approach to overcome this limitation. Using reported methodologies for the covalent functionalization of the tungstovanadate Dawson POM [P2V3W15O62]9-, we prepared a series of conjugated dipyridyl modified POMs, with organic spacers of different lengths and geometries. Electrochemical oxidation of the visible light photosensitizer Zinc-octaethylporphyrin (ZnOEP) in presence of theses POM-dipyridyl molecular building blocks and native organic dipyridyl spacers lead to the formation of uniform films deposited on ITO electrodes. The dipyridyl group s reactivity depends on their size and geometry and has an impact on the film thickness. This thickness can also be finely tuned by changing the experimental deposition conditions. We investigated the ability of these films to generate a photocurrent under visible light irradiation. We found that dipyridyl spacer geometry and film thickness were key parameters for photocurrent intensity.PARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF