Open-chain polyamine ligands bearing an anthracene unit - Chemosensors for logic operations at the molecular level

In this work the absorption and the fluorescence emission properties as well as the protonation sequence of three open chain polyamine ligands of different dimensions bearing an anthracene unit were studied. The protonation and stability constants with Ni²⁺, Cu²⁺, Zn₂₊, and Cd²⁺ have been determined in 0.15 mol·dm^-3 NaCl at 298.1±0.1 K. The values of both protonation and stability constants follow the expected trends according to the number of nitrogen donors, sequence of chelate rings and hydrophilic-hydrophobic balance. Chelation enhancement of the fluorescence emission (CHEF) was observed for some complexes of these ligands with Zn²⁺ and Cd²⁺. In contrast the analog complexes containing Cu²⁺and Ni²⁺ exhibit a chelation enhancement of the quenching (CHEQ) except for the complexes with the largest chain where some protonated metal complexes are emissive. These systems are explored from the point of view of chemosensors for logic operations at the molecular level.