Search

Herein, we present a new strategy for the development of efficient heavy-atom free singlet oxygen photosensitizers based on rigid borafluorene scaffolds. Physicochemical properties of borafluorene complexes can be easily tuned through the choice of ligand, thus allowing exploration of numerous organoboron structures as potent 1O2 sensitizers. The singlet oxygen generation quantum yields of studied complexes vary in the range of 0.55-0.78. Theoretical calculations reveal that the introduction of the borafluorene moiety is crucial for the stabilization of a singlet charge transfer state, while intersystem crossing to a local triplet state is facilitated by orthogonal donor-acceptor molecular architecture. Our study shows that quantitative oxidation of selected organic substrates can be achieved in 20-120 min of irradiation with only 0.05 mol % loading of a photocatalyst.

The photoactive layers of poly(terthiophene) with covalently attached fullerene photosensitizers were formed on indium–tin oxide (ITO) substrate in the process of electrochemical polymerization fro...

Herein, we examine the synthesis of new polymers and characterize their physicochemical properties. A series of novel polymers based on polymethylsiloxane by catalytic hydrosilylation were successfully designed and synthetized. In order to enhance the polymers solubility, perylene diimide acted as the active functional group and poly(ethylene glycol) acted as the property modifying agent. Their structure was studied using 1H NMR and infrared spectroscopy. Grafting of PDI-allyl on polysiloxane led to mostly insoluble polymer. In contrast, the addition of poly(ethylene glycol)s co-grafts promoted good solubility in common solvents. UV-Vis and fluorescence spectroscopy, and atomic force microscopy were used to characterize the polymers. The generation of singlet oxygen by the prepared polymers, in which perylene diimide was the photosensitizer, demonstrated their applicability.

The selected group of four amine-derivatives of phenothiazine was covalently grafted to the glassy carbon surface in the four-step procedure consisting of the electrochemical reduction of the diazonium salt followed by the electrochemical and chemical post-modification steps. The proposed strategy involves the bonding of linker molecule to which the photosensitizer is attached. The synthesized organic layers were characterized by means of cyclic voltammetry, XPS and Raman Spectroscopy. It was shown that the phenothiazines immobilized via proposed strategy retain their photochemical properties and are able to generate 1 O 2 when activated by the laser radiation. The effectiveness of in situ singlet oxygen generation by those new solid photoactive materials was determined by means of UVVis spectroscopy. The reported, covalently modified solid surfaces may find their application as the singlet oxygen photogenerators in the fine chemicals’ synthesis or in the wastewater treatment.

Five selected amine-derivatives of phenothiazine were electropolymerized on an ITO/glass substrate and then used in the daylight-activated process to produce in situ singlet oxygen which degrades phenol in a solution. The phenothiazines were immobilized in a simple electrochemical procedure in an acidic solution which led to the formation of an ultrathin transparent polymeric film. All films obtained on the ITO substrate including azure A (AA), azure C (AC), methylene blue (MB), toluidine blue (TBO), and thionine (Th) had a comparable surface coverage at the level of picomoles/cm 2 . The activity of these materials was then compared and presented in terms of an efficiency of the phenol degradation process in an aqueous solution by photogenerated singlet oxygen. That efficiency was determined by the UV–vis spectroscopy employing a phenol/4-aminoantipyrine complex. All the phenothiazine ultrathin polymeric films were capable of generating the singlet oxygen in the aqueous solution under daylight activation, which was used in the consecutive process of phenol degradation. The highest efficiency at a level of 51.4% and 45.4% was found for the AC/ITO and MB/ITO layers, respectively.

Four amine-derivative phenothiazines were converted to the corresponding diazonium salt forms prior to their electrochemical grafting on the GC electrode with the aim to assess their ability to generate singlet oxygen. It was demonstrated by cyclic voltammetry and XPS spectroscopy that the molecular layers were effectively bound to the GC surface by applying the reductive potential in situ in the reaction diazo-mixture. The chosen procedure without the product separation step, appears to be especially useful due to the high solubility of the resulted phenothiazine diazonium salts. The effectiveness of singlet oxygen generation was measured for all of the grafted surfaces by UVVis spectra monitoring of the adjacent solution phase of 1,3-diphenylisobenzofuran (DPBF), which is well known trapping molecule used in detection of singlet oxygen. The data presented in the work prove that all of the molecular layers are effective singlet oxygen generators that might be used for various areas of applications where a highly oxidative reactant is required.

New conjugated polymers with perylene diimides (PDI) as pendant groups were synthesized and deposited on glass substrates by the spin coating. The resulting thin films were characterized by UV–vis, Raman spectroscopy, atomic force microscopy and profilometry. It was shown that PDI photosensitizers retain its photoactivity after covalent immobilization and the formed layers can be applied as efficient and environmentally stable source of singlet oxygen, 1O2, as tested with 1,3-diphenylisobenzofuran (DPBF) specific trap. Additionally, α-terpinene heterogeneous photooxidation was studied as the practical use of singlet oxygen generated by this novel PDI-based materials. The use of such heterogeneous source of singlet oxygen can be beneficial for the fine chemicals synthesis, due to simplified products isolation and purification step.

Thionine (Th) was electrochemically grafted to the glassy carbon (GC) surface from its corresponding diazonium salt to investigate it as a singlet oxygen source under light excitation. As confirmed by cyclic voltammetry data the Th molecules may form a monolayer structure in the reduction process carried out directly from the diazotization reaction mixture without a time-consuming separation step. It was found that illuminated grafted Th at a level of monolayer coverage on GC surface is able to generate singlet oxygen at a constant rate. To determine efficiency of the photogeneration process a singlet oxygen selective trap, 1,3-diphenylisobenzofuran (DPBF), was employed, which was monitored using UVVis spectroscopy. The progress of the trap decay was determined in terms of its half-life. Keywords: Singlet oxygen, Phenothiazines, Photosensitizers, Photochemical generation, Electrografting

The selected group of five amine-derivative phenothiazines was used to form their electropolymerized films in aqueous acidic solution with the aim to assess their ability to generate singlet oxygen. The films were characterized using cyclic voltammetry, UVVis spectroelectrochemistry, and Raman spectroscopy. The data of all the films were compared with properties of their monomer analogs. It was demonstrated that the electrochemically prepared films similarly to the known process of the corresponding monomers in solution phase are able to generate singlet oxygen in a photochemical surface process activated by laser radiation. These photogeneration process of the short-living species was monitored using the selected trap, which is detectable using UVVis spectroscopy. The effectiveness of the surface photogeneration reaction for each polymeric structure was determined in terms of half-life of the trap decay. The presented heterogeneous process of singlet oxygen photogeneration is believed to extend the area of applications of that highly oxidative reactant as compared to known homogeneous systems employing unbounded active species.

Fullerene, C60 photosensitizer was incorporated into poly(Azure A) in the process of electrochemical polymerization from the solution of corresponding dye and fullerene. The synthesized organic layer (PAA_C60/ITO) was characterized by means of cyclic voltammetry, UV–Vis, Raman and X-ray photoelectron spectroscopies. It was shown that PAA_C60/ITO exhibits strong absorption in both UV and Vis regions and that both immobilized photosensitizers, i.e. Azure A and C60, retain their photochemical activity towards 1O2 generation under illumination as tested with 2,3,4,5-tetraphenylcyclopentadienone (TPCPD) singlet oxygen quencher. The electrodeposited photoactive layer composed of two photosensitizers was investigated as a source of 1O2 in the process of α-terpinene oxidation.

A selenophene-containing fullerene dyad (C60Se) was electrochemically co-deposited with bis-selenophene (BisSe) to form a visible light absorbing poly(selenophene) layer with incorporated fullerene photosensitizers on platinum (Pt) or indium-tin oxide (ITO) substrates. The resulting photoactive films (P(C60Se_BisSe)) were characterized by cyclic voltammetry, UV–Vis, IR, Raman and X-ray photoelectron spectroscopies. The efficiency of P(C60Se_BisSe) towards singlet oxygen photogeneration was investigated by applying reactions with chemical traps, i.e. α-terpinene and 1,3–diphenylisobenzofuran (DPBF), monitored by UV–Vis spectroscopy. The composition of the electropolymerized layer was controlled by varying the monomers ratio in the feed solution and it had a strong influence on the spectroscopic and photosensitizing properties of the deposited film. It has been shown that the efficiency of the visible light-driven singlet oxygen generation can be increased by optimizing the ratio between C60 photosensitizers and organic units in the layer.