Diogen Laertije - Životi i mišljenja istaknutih filozofa

The vast majority of polyhedral assemblies prepared by combining organic bent ligands and “photophysically innocent” palladium­(II) metal ions are nonemissive. We report here a simple strategy to switch on the luminescence properties of a polyhedral assembly by combining a thermally activated delayed fluorescence (TADF) organic emitter based on a dipyridylcarbazole ligand scaffold with Pd²⁺ ions, giving rise to a luminescent Pd₆L₁₂ molecular cube. The assembly is capable of encapsulating within its cavity up to three molecules per cage of fluorescein, in its neutral lactone form, and up to two molecules of Rose Bengal in its dianionic quinoidal form. Photoinduced electron transfer (PeT) between the photoactive cage and the encapsulated Fluorescein and photoinduced energy transfer (PET) from the cage to encapsulated Rose Bengal have been observed by steady-state and time-resolved emission spectroscopy

Residual Ligand Entropy in the Binding of <i>p</i>-Substituted Benzenesulfonamide Ligands to Bovine Carbonic Anhydrase II

In studies on the thermodynamics of ligand−protein interactions, it is often assumed that the configurational and conformational entropy of the ligand is zero in the bound state (i.e., the ligand is rigidly fixed in the binding pocket). However, there is little direct experimental evidence for this assumption, and in the case of binding of <i>p</i>-substituted benzenesulfonamide inhibitors to bovine carbonic anhydrase II (BCA II), the observed thermodynamic binding signature derived from isothermal titration calorimetry experiments leads indirectly to the conclusion that a considerable degree of residual entropy remains in the bound ligand. Specifically, the entropy of binding increases with glycine chain length <i>n</i>, and strong evidence exists that this thermodynamic signature is not driven by solvent reorganization. By use of heteronuclear ¹⁵N NMR relaxation measurements in a series (<i>n</i> = 1−6) of ¹⁵N-glycine-enriched ligands, we find that the observed thermodynamic binding signature cannot be explained by residual ligand dynamics in the bound state, but rather results from the indirect influence of ligand chain length on protein dynamics