Layered silicate films with photochemically active porphyrin cations

Abstract

The objective of this study was to prepare and characterize hybrid films based on layered silicates with a tetracationic porphyrin dye 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP) intercalated in the inorganic matrix. The properties of the TMPyP cations in the materials were compared with those of other systems (solutions, colloids) characterized mainly by absorption and fluorescence spectroscopies. Linearly polarized absorption spectroscopy, X-ray diffraction (XRD), and fluorescence microscopy were used as well. Using appropriate layered silicate templates, applying the premodification of the inorganic component with hydrophobic alkylammonium surfactants, and selecting an appropriate method, one can prepare the materials of broadly variable spectral properties of the dye. The spectral variation takes place while preserving the photochemical activity of TMPyP. The interpretations of spectral changes are based on the structural changes of the TMPyP molecules adsorbed on layered silicate surface related to the flattening of cationic pyridinium substituents.

Kinetic Analysis by Laser Flash Photolysis of Porphyrin Molecules’ Orientation Change at the Surface of Silicate Nanosheet

“…We have obtained porphyrin molecule assemblies by using layered silicate, fully exfoliated, to form a nanosheet. The silicate nanosheet (also known as a clay nanosheet) has been used extensively as a host material for guest molecules. − In the host–guest hybrid complex, cationic porphyrins are used as guests to exploit electrostatic attractions with the nanosheet. The advantage of the hybrid complex in dye assembly formation is that the electrostatic attraction between the dye and nanosheet becomes much larger than the interaction between dyes that induces self-aggregation and shortens the excitation lifetime.…”

Size-Matching Effect on Inorganic Nanosheets: Control of Distance, Alignment, and Orientation of Molecular Adsorption as a Bottom-Up Methodology for Nanomaterials

“…As a host material, clay minerals − that are typical inorganic layered materials have been mainly used. Dye molecules such as porphyrin derivatives , are used as functional dye guest molecules. − In this article, the unique structure control of dye molecule assembly formed on the clay surface and their photochemical reactions and solvatochromic functions are reported.…”

The Mechanism of the Porphyrin Spectral Shift on Inorganic Nanosheets: The Molecular Flattening Induced by the Strong Host–Guest Interaction due to the “Size-Matching Rule”

“…We have been investigating inorganic/organic hybrids from a viewpoint of photochemistry. − In inorganic/organic systems, an interaction between the host materials and the guest molecules is crucially important to determine the various properties of the guest molecules. Over a number of years, there has been a large volume of literature concerning the interactions between organic molecules and inorganic materials. − With regard to the photochemical properties, the spectral shift of the absorption in functional dye complexes on the surface of inorganic nanosheets has been extensively studied. In the past, various mechanisms have been proposed for inducing the spectral shift of dyes on the surface of inorganic nanosheets as follows. − (i) “An effect of an aggregation of molecules”. − This is the most usual mechanism for the spectral shift on the surface of inorganic nanosheets.…”