Intramolecular interactions in porphyrin – labelled polymers studied by spectroscopic, photothermal and photoelectric examinations

The aim of this study is characterization of photophysical properties of newly synthesized porphyrin-labelled polymers in aqueous solution, methanol and dioxane. The copper, zinc and free base tetraphenylporphyrins (CuTPP, ZnTPP and H$_{2}$TPP) covalently linked to polyethylene glycol (PEG) or poly(N)isopropylacrylamide (PNIPAM) were investigated. Absorption, fluorescence and photothermal properties were determined in order to follow deactivation pathways of radiative and non–radiative processes of the excited states of the porphyrin molecules in the polymeric systems and some intramolecular interactions. The spectroscopic experiments were supported by the photoelectric studies of the investigated systems in a photoelectrochemical cell. It was shown that the polymers cause the changes in electronic distribution in porphyrin covalently linked to the polymeric chain and can lead to enhancement of the photoactivity of the porphyrin species in light energy to electric energy conversion. The absorption, fluorescence and photothermal experiments showed the existence of the aggregated porphyrins, charge transfer in the dye-polymer systems

Influence of Silver Colloid on Fluorescein Spectral Properties

In order to check if the observed earlier changes in fluorescence intensities of fluorescein solution due to the addition of colloidal suspension of silver are related to the generation of surface plasmon coupled emission, the steady state photothermal spectra and fluorescence decay times of such samples were measured. The Gaussian components of photoacoustic spectra for solutions with and without silver colloid addition were determined and compared with components of absorption and fluorescence excitation spectra of the same samples. The efficiencies of thermal and radiative deactivation of various samples were discussed. The fluorescence decay times measured at the wavelength of excitation not exhibiting the increase in photonic mode density depend only on the dye concentration. Decays exhibit changes as a result of silver addition with excitation in the region in which enhancement of fluorescence is observed. These changes are due not only to the change in the fluorescence yield generated by interactions with plasmons but also to those in thermal deactivation of the sample related to the colloid presence

Organic photocatalysts for the oxidation of pollutants and model compounds

The use of organic photocatalysts for the oxidation of pollutants and model compounds, with special emphasis on the involved concepts and mechanistic aspects, is reviewed. Photoinduced electron transfer involving the singlet excited state of phthalocyanines has been postulated in the photodegradation of phenols. The reactivity of OH - radical with different pollutants has been quantitatively determined by competition experiments, looking at the decrease of the typical transient absorption of the stilbene adduct at 390 nm. As regards heterogeneous media, after excitation at 355 nm of phthalocyanines immobilized in zeolites, the characteristic singlet oxygen luminiscence is monitored at 1270 nm. TPP has been included within extralarge pore zeolitic aluminosilicates, such as MCM-41. These materials provide an adequate balance between moderate cage effect and facilitation of molecular traffic through the mesopores.Financial support from the Spanish Government (CTQ2009- 13699, CTQ2009-13459-C05-03/PPQ, RIRRAF RETICS), and the Generalitat Valenciana (Prometeo Program) is gratefully acknowledged. Dedicated to Prof. Avelino Corma on the occasion of his 60th birthday.Marín García, ML.; Santos-Juanes Jordá, L.; Arqués Sanz, A.; Amat Payá, AM.; Miranda Alonso, MÁ. (2012). Organic photocatalysts for the oxidation of pollutants and model compounds. Chemical Reviews. 112(3):1710-1750. doi:10.1021/cr2000543S17101750112