Encapsulation of l-valine, d-leucine and d-methionine by cucurbit[8]uril

The binding interactions of cucurbit[8]uril (Q[8]) with l-valine, d-leucine, and d-methionine, both in aqueous solution and solid state, have been studied by 1H NMR spectroscopy and X-ray crystallography.

Noncovalent Interactions at Lanthanide Complexes

Lanthanide complexes have attracted a widespread attention due to their structural diversity, as well as multifunctional and tunable properties. The development of lanthanide based functional materials has often relied on the design of the secondary coordination sphere of the corresponding lanthanide complexes. For instance, usually simple lanthanide salts (solvento complexes) do not catalyze effectively organic reactions or provide low yield of the expected product, whereas the presence of a suitable organic ligand with a noncovalent bond donor or acceptor centre (secondary coordination sphere) modifies the symmetry around the metal centre in lanthanide complexes which then successfully can act as catalysts in both homogenous and heterogenous catalysis. In this minireview, we discuss several relevant examples, based on X-ray crystal structure analyses, in which the hydrogen, halogen, chalcogen, pnictogen, tetrel and rare-earth bonds, as well as cation-π, anion-π, lone pair-π, π-π and pancake interactions, are used as a synthon in the decoration of the secondary coordination sphere of lanthanide complexes.

Protein recognition by cucurbit[6]uril: high affinity N-terminal complexation

The donut-shaped cucurbit[n]urils (Qn, n = 6-8) are rigid macrocyclic receptors with widespread use in protein recognition. To date, most applications have centred on the encapsulation of N-terminal aromatic residues by Q7 or Q8. Less attention has been placed on Q6, which can recognize lysine side chains due to its high affinity for alkylamines. In this work, we investigated protein-Q6 complexation by using NMR spectroscopy. Attempts to crystallize protein-Q6 complexes were thwarted by the crystallization of Q6. We studied four proteins that vary in size, net charge, and lysine content. In addition to Q6 interactions with specific Lys or dimethylated Lys residues, we report striking evidence for N-terminal recognition. High affinity (micromolar) binding occurred with the N-terminal Met-Lys motif present in one of the four model proteins. Engineering this feature into another model protein yielded a similar high affinity site. We also present evidence for Q8 binding at this N-terminal feature. These data expand the cucurbituril toolkit for protein sensing.

Engineered assembly of a protein–cucurbituril biohybrid

Additional Q7 binding sites drive protein aggregation in solution and statistical disorder in the crystalline biohybrid suggest new possibilities for protein-based materials.

Harnessing uranyl oxo atoms via halogen bonding interactions in molecular uranyl materials featuring 2,5-diiodobenzoic acid and N-donor capping ligands

The supramolecular assembly of molecular uranyl species via halogen-oxo interactions and spectroscopic manifestations thereof are probed in the solid state.

Cucurbit[n]uril-capped upconversion nanoparticles as highly emissive scaffolds for energy acceptors

Spontaneous adsorption of cucurbit[n]uril CB[n] (n=6, 7, and 8) on the surface of naked upconversion nanoparticles (UCNPs), in particular, NaYF4:Er3+(2%),Yb3+(18%) gave rise to UCNP@CB[n] exclusion complexes. These complexes proved to be highly stable as well as highly emissive under near-infrared excitation. By using two tricyclic basic dyes (specifically, methylene blue and pyronin Y) as a proof of concept, we demonstrate that the UCNP@CB[n] (n=6, 7) nanohybrids can form exclusion complexes with this type of dyes via the CB carbonyl free portal, i.e., UCNP@CB@dye hybrids, thus making it possible to locate a high concentration of the dyes close to the UCNP and, consequently, leading to efficient energy transfer from the UCNP to the dye.

Exploring supramolecular assembly and luminescent behavior in a series of RE-p-chlorobenzoic acid-1,10-phenanthroline complexes

Eleven new rare earth (RE)-p-chlorobenzoic acid-1,10-phenanthroline complexes have been synthesized and their structural, supramolecular and luminescent properties have been explored.