Photocatalytic properties of supramolecular nanoassociates based on gold and platinum nanoparticles, capped by amphiphilic calix[4]resorcinarenes, towards organic dyes

Recognition of Heavy Metals by Using Resorcin[4]arenes Soluble in Water

The complexing properties of two water-soluble resorcin[4]arenes (tetrasodium 5,11,17,23-tetrakissulfonatemethylen 2,8,14,20-tetra(butyl)resorcin[4]arene, Na₄BRA, and tetrasodium 5,11,17,23-tetrakissulfonatemethylen-2,8,14,20-tetra(2-(methylthio)ethyl)resorcin[4]arene, Na₄SRA) with polluting heavy metals such as Cu²⁺, Pb²⁺, Cd²⁺ and Hg²⁺ were studied by conductivity, and the findings were confirmed by using other techniques to try to apply this knowledge to removing them. The results indicate that Na₄BRA is able to complex Cu²⁺ in a 1:1 ratio and Pb²⁺ in a 1:2 ratio, while Na₄SRA complexes Hg²⁺ in a 1:1 ratio. On the contrary, no indications have been observed that either of the resorcin[4]arenes studied complexes the Cd²⁺ ions. The results suggest that the bonds established between the sulfur atoms located at the lower edge of the SRA^4- and the solvent hydrogens could prevent the entry of the guest into the host cavity. However, in the case of Hg²⁺ ions, the entry is favoured by the interactions between the sulfur donor atoms present on the lower edge of Na₄SRA and the Hg²⁺ ions. Therefore, it can be said that Na₄BRA is selective for Cu²⁺ and Pb²⁺ ions and Na₄SRA is selective for Hg²⁺ ions.

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

Due to the unique characteristics of macrocycles (e.g., the ease of modification, hydrophobic cavities, and specific guest recognition), they can provide a suitable environment to realize photocatalysis via noncovalent interactions with different substrates. In this minireview, we emphasized the photochemical transformation and catalytic reactivity of different guests based on the binding with various macrocyclic hosts as well as on the role of macrocyclic-hosts-assisted hybrid materials in energy transfer. To keep the clarity of this review, the macrocycles are categorized into the most commonly used supramolecular hosts, including crown ethers, cyclodextrins, cucurbiturils, calixarenes, and pillararenes. This minireview not only summarizes the role that macrocycles play in photocatalytic reactions but also clarifies the photocatalytic mechanisms. Finally, the future research efforts and new pathways to apply macrocycles and supramolecular hybrid materials in photocatalysis are also discussed.