Rana Farha

Synthesis and photocatalytic properties of mixed polyoxometalate-porphyrin copolymers obtained from Anderson-type polyoxomolybdates.

Hybrid polyoxometalate-porphyrin copolymeric films are obtained by the electro-oxidation of zinc octaethylporphyrin (ZnOEP) and zinc 5,15-dipyridinium octaethylporphyrin (5,15-ZnOEP(py)(2)(2+)) in the presence of the polyoxometalate [MnMo(6)O(18){(OCH(2))(3)CNHCO(4-C(5)H(4)N)}(2)](3-) (Py-POM-Py). These films allow the photocatalytic reduction of Ag(I)(2)SO(4) under visible irradiation in air in the presence of propan-2-ol at the 2D interface between water and the copolymeric films. The formation of metallic Ag(0) nanowires and triangular nanosheets is observed.

Formation and photocatalytic properties of nanocomposite films containing both tetracobalt Dawson-derived sandwich polyanions and tetracationic porphyrins.

Films based on electrostatic interactions between tetracationic zinc porphyrins, ZnOEP(py)(4)(4+) or ZnTMePyP(4+), and the tetracobalt Dawson-derived sandwich polyanion αββα-[Co(4)(H(2)O)(2)(P(2)W(15)O(56))(2)](16-) are formed by the so-called layer-by-layer method. These films have been characterized by UV-visible absorption spectroscopy, atomic force microscopy and electrochemistry. The composition of the film was measured by X-ray photoelectron spectrum (XPS). The XPS data confirm the presence of the expected elements. The photocatalytic properties of these films have been also studied for the reduction of silver and gold ions. Indeed, in these systems, porphyrins can be excited by visible light and then play the role of photosensitizers able to give electrons to POM known to be good catalysts. Silver nanowires and gold nanosheets have been obtained.

Bis-porphyrin copolymers covalently linked by pyridinium spacers obtained by electropolymerization from β-octaethylporphyrins and pyridyl-substituted porphyrins

Five bis-porphyrin copolymers have been obtained by an electropolymerization process using zinc β-octaethylporphyrin (ZnOEP) type macrocycles and porphyrins functionalized by several pyridyl groups. This electropolymerization process is based on a nucleophilic attack of the pyridyl groups onto electrogenerated ZnOEP dications at their meso-positions. It is the first time that bis-porphyrin copolymers have been obtained. In this study, the copolymers have been characterized by electrochemistry, UV-visible absorption spectroscopy and atomic force microscopy. In particular, interactions between pyridinium spacers are thoroughly discussed.

Generation of Photocurrent by Visible‐Light Irradiation of Conjugated Dawson Polyoxophosphovanadotungstate–Porphyrin Copolymers

Four hybrid polyoxometalate-porphyrin copolymer films were obtained by the electrooxidation of zinc octaethylporphyrin in the presence of four different Dawson-type polyoxometalates bearing two pyridyl groups (POM(py)2) with various spacers. The POM monomers were designed around 1,3,5-trisubstituted benzene rings. Two of the substituents of the benzene ring are linked to the pyridyl groups, and the third is connected to the POM subunit. The four monomers vary in the relative positions of the nitrogen atoms of the pyridine rings or in the distance from the carbonyl group. The monomers were fully characterized by (1)H, (31)P, and (13)C NMR spectroscopy, electrospray mass spectrometry, IR and UV/Vis spectroscopy, and electrochemistry. The copolymers were characterized by UV/Vis spectroscopy, X-ray photoelectron spectroscopy, electrochemistry, and AFM. Their photovoltaic performance under visible light irradiation was investigated by photocurrent transient measurements under visible illumination.

Electrosynthesis and electrochemical properties of porphyrin dimers with pyridinium as bridging spacer

Two porphyrin dimers (more precisely two isomers) with pyridinium as bridging spacer have been obtained by controlled potential electrolysis. This method is based on a nucleophilic substitution of a porphyrin substituted by a pyridyl group (namely 5,10,15-tritolyl-20-(4-pyridyl)porphyrin (H2T3P-4-Py) or 5,10,15-tritolyl-20-(3-pyridyl)porphyrin (H2T3P-3-Py)) on an electrogenerated radical cation of a zinc β-octaethylporphyrin (ZnOEP). The new compounds have been characterized by HR-MS, 1H NMR, UV-vis and fluorescence spectroscopies. Difference of electrochemical behaviour of the pyridinium spacers between the two dimers has been also discussed.

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

Electropolymerization of porphyrins has been initially developed by Macor and Spiro, who have polymerized vinyl-substituted porphyrins, the coupling occurring after the formation of vinyl radicals by electrooxidation (Macor & Spiro, 1983). Afterwards, other methods of electropolymerization have been published, for example from hydroxy-, amino-, pyrrole- or thiophene-substituted porphyrins (Bedioui et al., 1995; Bettelheim et al., 1987; Li et al., 2005). In this context, we have developed an original methodology for the electropolymerization of porphyrins, based on nucleophilic attacks of di-pyridyl compounds directly onto electrooxidized porphyrins. This chapter presents an overview of this new method of electropolymerization.

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

This paper reports the formation of hybrid polyoxometalate-porphyrin copolymeric films obtained by the electro-oxidation of zinc-β-octaethylporphyrin (ZnOEP) in the presence of a functionalized Dawson-type polyoxometalate bearing two pyridyl groups (POMdbme3,3, Py-POM-Py) which will be compared to the copolymer obtained from ZnOEP and a dipyridyl compound without POM (ibme3,3). The resulting film has been characterized by UV-visible absorption spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. Electrochemical quartz crystal microbalance was employed to investigate the poly-porphyrin-POMs deposition mass.Graphical Abstract

Design of self-assembled photonic crystals for chemical sensing

We investigated different methods to engineer efficiently a planar defect between two artificial opals. The samples were characterized by atomic force microscopy, scanning electron microscopy and specular reflection spectroscopy. They presented pronounced defect modes within the photonic stopband. These architectured structures were applied to the manipulation of nanocrystals fluorescence and to the detection of bisphenol A traces.