Photoactive Hexanuclear Molybdenum Nanoclusters Embedded in Molecular Organogels

Abstract

Hexanuclear molybdenum clusters are attractive species due to their outstanding photonic properties, and in the past they have been attached to a variety of supports such as organic polymers and inorganic nanoparticles, as described in the recent literature. Here, a cluster of formula TBA2[Mo6I8Ac6] (TBA = tetrabutylammonium, Ac = acetate) has been supported on molecular organogels for the first time, resulting in a new soft materials with remarkable photoactivity. Electron and confocal microscopic analyses showed the alignment of the nanoclusters to 1D selfassembled fibres formed by the organic gelator, and emission spectroscopy corroborated the interaction of the emissive clusters with such fibrillary structures. The new hybrid system is a deep-red emissive material (phosphorescence maximum at ca. 680 nm), with chromatic coordinates x=0.725, y=0.274, capable of generating efficiently singlet oxygen (1 O2) upon illumination with white light, as demonstrated by the photo-oxygenation of 9,10dimethylanthracene and 1,5-dihydroxynaphthalene. The organogels can been made in dichloromethane and toluene, and in both solvents display phosphorescence emission and photocatalytic properties.

Photodynamic Inactivation of Staphylococcus aureus Biofilms Using a Hexanuclear Molybdenum Complex Embedded in Transparent polyHEMA Hydrogels

“…This fact would point out to some kind of additional cross-linking effect of the molybdenum cluster on the structure of the materials, the study of which is out of the scope of this paper. Regarding the emission measurements, the samples under UV excitation emit a reddish phosphorescence observable even with the naked eye (see Figure S2), and the spectrum of such luminescence reveals the typical broad band of emissive hexanuclear molydbenum complexes between 600 and 750 nm. − ,− Minor differences can be found between the polymeric samples and also when compared to a solid sample of 1 and to an ethanolic solution of the photosensitizer (see Figure ), probably due to different solvation environments, in agreement with the literature. − ,− In the case of the materials here described, the presence of this emissive band confirms that the structural integrity of the photosensitizer remains intact after the polymerization reaction. Also, it could be speculated that, due to the low concentration of 1 and to the anionic nature of this photosensitizer, aggregation does not take place (future microscopic studies will shed light on the distribution of 1 within these and other polyHEMA matrixes).…”

“…The group of hexanuclear molybdenum clusters described by the formula [Mo 6 L i 8 L a 6 ] n − (L i and L a are inner and apical ligands, respectively) has been receiving increasing attention due to their outstanding photophysical properties. A great number of such species have been described so far, both in solution − and immobilized in a series of supports, such as polyurethane, poly­(methyl methacrylate), zinc oxide, and other materials. − After excitation with visible light, the triplet excited state is very efficiently populated, and many of such complexes, especially the iodides (L = I), are able to emit phosphorescence in the deep-red region of the spectrum, even at room temperature. Another relevant property of this class of complexes is their ability to generate 1 O 2 after irradiation.…”

Pyrene-Based Co-Assembled Supramolecular Gel; Morphology Changes and Macroscale Mechanical Property

“…The tube inversion method with heating and cooling of co-assembled gel provided confirmation of reversible sol-gel transition. Co-assembled gel 1 seemed to break down from 119 ℃ at molar ratios [2]/[1] = 0.8. The sol-gel transition temperature of co-assembled gel in the presence of 0.8 equiv.…”

“…The morphology of co-assembled supramolecular gels changed from spherical nanoparticles to three-dimensional network nanofibers as the ratio of 2 increased. In addition, the mechanical properties of co-assembled supramolecular gels was controllable by modification of the ratio of compound [2]: [1], due to the formation of pyrene-excimer and increased flexibility of supramolecular packing structure. Thus, further development of co-assembly supramolecular gels using the formation of pyrene-excimer can offer materials for optical applications and dual-functional gels by implementing functional derivatives.…”

“…Supramolecular gels are composed of low-molecular-weight organic compounds and use self-assembly processes, and have thus been an area of research interest due to their potential applications in photonics [1][2][3], optoelectronics [4][5][6][7], photodynamic therapy [8][9][10], and sensors [11,12]. Although supramolecular gels can be obtained from polymers, preparation using a low-molecular-weight gelator offers several advantages, such as easy synthesis, reversibility, and better control over the resulting physical and chemical properties [13][14][15][16].…”