Photophysical Properties and Aggregation Behavior of Transition Metal Tetraphenylporphyrin Tetrasulfonate Complexes in Microheterogeneous Media

Abstract

This paper considers the influence of various surfactants and polyelectrolytes on the photophysical properties and the aggregation state of transition metal complexes of meso-5,10,15,20-tetrakis-(4-sulfonatophenyl) porphyrin (MeTPPS). Porphyrin transition metal complex aggregation stability in acidic medium is also compared for a number of metal cations. The mechanism of J-aggregate formation and the nature of porphyrin-surfactant interactions in microorganized systems are discussed in details.Keywords: Transition metal porphyrin complexes, ZnTPPS, J-aggregates, ionic associates. Фотофизические свойства и агрегационная устойчивость IntroductionPorphyrin based supramolecular assemblies in recent years have been considered as novel mesoscopic materials with tunable electronic and optical properties, useful as photosensitizers, optical switches, molecular sensors, artificial light-harvesting systems and photovoltaic device components. [1][2][3] Such smart materials can include either homoporphyrin aggregates (H-or J-type ones) or multiporphyrin assemblies, [4] as well as heteroaggregates [5] and ionic associates with various non-porphyrin compounds. [6] Since both photophysical and photochemical properties of various porphyrin derivatives strongly depend on the chromophore aggregation state determined predominantly by the medium acidity, ionic strength and the presence of template molecules, controlled reversible aggregation of porphyrin supramolecular assemblies is still of great research interest.To date among the known water-soluble porphyrin derivatives the most well-studied one is meso-5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrin (TPPS). During the past decade much work has been done on TPPS interactions with surfactants, [7][8][9][10][11] polyelectrolytes [12][13][14][15] and especially biomacromolecules. [16][17][18] The increasing research interest in porphyrin behavior within microorganized systems is due to their possible application as photosensitizers in photodynamic therapy (PDT), [19] since the microheterogeneous medium is known to favor supramolecular ionic associate and 341 Макрогетероциклы / Macroheterocycles 2013 6(4) 340-344 M. A. Gradova, A. V. Lobanov heteroaggregate formation, especially at low pH abundant in cancer cells. [20][21][22] Despite the large amount of available experimental data, we still lack a unified detailed description of the mechanism of porphyrin aggregate formation in microorganized biomembrane-mimetic media.The main aim of this work was to compare the photophysical properties and the aggregation state of water soluble transition metal complexes of tetraphenylporphyrin tetrasulfonate in various microheterogeneous systems, such as surfactant (SDS, CTAB, TX-100) and polyelectrolyte (PDDA, PVP, PEG) solutions with different surface charge. We especially focused on influence of the cation nature on the porphyrin metal complex stability in acidic medium, J-type aggregate formation and their morphology. ExperimentalTransition metal complexes of cobalt, nickel and zinc with a...