Louis Adriaenssens

Hydrogen bonded supramolecular capsules with functionalized interiors: the controlled orientation of included guests

This tutorial review aims to present and describe selected examples of still quite rare endo-functionalized supramolecular capsules. Only capsules assembled through the use of neutral or polar hydrogen bonding interactions are covered. The ability of these capsules to orient and control the position of the encapsulated guest molecules represents their stand-out feature. Thus, the way in which guests interact with the functionalized interior of the capsules is discussed in detail. Several of the described capsular assemblies display chiral architectures. The manner in which chirality is manifested in these assemblies is far from trivial. For this reason, we also offer explanations of the chiral features expressed by the relevant capsules and their encapsulation complexes.

Recognition and Sensing of Creatinine

Current methods for creatinine quantification suffer from significant drawbacks when aiming to combine accuracy, simplicity, and affordability. Here, an unprecedented synthetic receptor, an aryl-substituted calix[4]pyrrole with a monophosphonate bridge, is reported that displays remarkable affinity for creatinine and the creatininium cation. The receptor works by including the guest in its deep and polar aromatic cavity and establishing directional interactions in three dimensions. When incorporated into a suitable polymeric membrane, this molecule acts as an ionophore. A highly sensitive and selective potentiometric sensor suitable for the determination of creatinine levels in biological fluids, such as urine or plasma, in an accurate, fast, simple, and cost-effective way has thus been developed.

Single‐Molecule‐Magnet Behavior in the Family of [Ln(OETAP)2] Double‐Decker Complexes (Ln=Lanthanide, OETAP=Octa(ethyl)tetraazaporphyrin)

Double-decker complexes of lanthanide cations can be readily prepared with tetraazaporphyrins (porphyrazines). We have synthesized and characterized a series of neutral double-decker complexes [Ln(OETAP)2 ] (Ln=Tb(3+), Dy(3+), Gd(3+), Y(3+); OETAP=octa(ethyl)tetraazaporphyrin). Some of these complexes show analogous magnetic features to their phthalocyanine (Pc) counterparts. The Tb(3+) and Dy(3+) derivatives exhibit single-molecule magnet (SMM) behavior with high blocking temperatures over 50 and 10 K, respectively. These results confirm that, in double-decker complexes that involve Tb or Dy, the (N4)2 square antiprism coordination mode has an important role in inducing very large activation energies for magnetization reversal. In contrast with their Pc counterparts, the use of tetraazaporphyrin ligands endows the presented [Ln(OETAP)2] complexes with extraordinary chemical versatility. The double-decker complexes that exhibit SMM behavior are highly soluble in common organic solvents, and easily processable even through sublimation.

Characterization of a new ionophore-based ion-selective electrode for the potentiometric determination of creatinine in urine

The optimization, analytical characterization and validation of a novel ion-selective electrode for the highly sensitive and selective determination of creatinine in urine is presented. A newly synthesized calix[4]pyrrole-based molecule is used as an ionophore for the enhanced recognition of creatininium cations. The calculation of the complex formation constants in the polymeric membrane with creatininium, potassium and sodium confirms the strong selective interactions between the ionophore and the target. The optimization of the potentiometric sensor presented here yields an outstanding analytical performance, with a linear range that spans from 1µM to 10mM and limit of detection of 10-6.2M. The calculation of the selectivity coefficients against most commonly found interferences also show significant improvements when compared to other sensors already reported. The performance of this novel sensor is tested by measuring creatinine in real urine samples (N=50) and comparing the values against the standard colorimetric approach (Jaffés reaction). The results show that this sensor allows the fast and accurate determination of creatinine in real samples with minimal sample manipulation.

Binding of calix[4]pyrroles to pyridine N-oxides probed with surface plasmon resonance

Using a commercial instrument that integrates microfluidics with surface plasmon resonance (SPR) detection, we thermodynamically and kinetically characterise the interactions of water-soluble calix[4]pyrroles with surface-immobilized guests derived from pyridine N-oxide. This technique provides detailed information in real time and shows that, while thermodynamically similar, the binding process occurring with the surface-immobilised guests is kinetically very different to that in solution. Two different binding processes can be distinguished for the surface-immobilised guests. Both complexation processes provide 1:1 complexes with thermodynamic stabilities that are similar to each other and to the 1:1 complex formed in solution. However, the kinetic stabilities of the complexes formed with the surface anchored ligands are significantly higher. These observations are rationalized on the basis of the effects exerted by the dextran matrix employed for the ligands immobilisation on the small molecule complexes that are formed.