Hemicryptophanes with Improved Fluorescent Properties for the Selective Recognition of Acetylcholine over Choline

Alkynylgold(I) C3 -Chiral Concave Complexes: Aggregation and Luminescence

Chiral gold(I) acetylide trinuclear complexes 1-3 based on the cyclotribenzylene platform and terminal PR₃ ligands (R=Ph, Et, and Cy, respectively), were characterized and their light emission studied. They exhibited long-lived blue phosphorescence in CHCl₃ and a weak fluorescence in the UV. In MeOH/CHCl₃ mixtures of >1:1 volume ratio, 1 and 2 exhibited a new emission band at ca. 540 nm that developed at the expense of the UV emission. DLS studies demonstrated the presence of molecular aggregates of Ø 30-80 nm. The green emission observed in MeOH-rich solvent mixtures was therefore induced by aggregation, and could originate from Au⋅⋅⋅Au interactions. The AIE spectrum of 3 was observed only in solutions containing 99 % of MeOH, and correlated with its solid state emission. The AIE profiles of the enantiomers of 1 differed from that of rac-1, suggesting that the latter is a true racemate.

Fluorescent Molecular Cages with Sucrose and Cyclotriveratrylene Units for the Selective Recognition of Choline and Acetylcholine

The synthesis of four fluorescent diastereoisomeric molecular cages containing cyclotriveratrylene and sucrose moieties connected via the naphthalene linkers is reported. These diastereoisomers were found to be selective and efficient receptors for acetylcholine and choline. Compound P-5a has a better affinity for choline over acetylcholine, while cage M-5a exhibits a higher association constant for acetylcholine over choline. The highest selectivity value was observed for compound M-5a (K_ACh/K_Ch = 3.1). Cages P-5a, P-5b, M-5a, and M-5b were fully characterized by the advanced NMR techniques, and ECD spectroscopy was supported by DFT calculations. The binding constants K_a of these receptors were determined by fluorescence titration experiments in acetonitrile.