Synthesis of Water-Soluble Triazinophanes and Evaluation of Their Molecular Recognition Properties

Molecular recognition properties of water-soluble triazinophane 1a–1c, derivatized through the straightforward S_NAr reaction of common intermediate 5, were explored in aqueous media. Fluorescence titration of 1a–1c by using mono cationic aromatic hydrocarbon G1 and G2 as guests revealed that 1 prefers to form a host–guest complex with pyrene derivative G2 rather than anthracene derivative G1. Complex formation between the derivatives of 1 and G2 were in a 1:1 equimolar ratio with binding constants of ≈ 8 × 10³ (m^–1), regardless of the substitution groups on the triazine rings. In addition, we found that the molecular recognition of 1 was successfully fine-tuned through post-modification of the triazine rings. With dicationic anthracene G3 as a guest only 1b formed a host–guest complex (K_a = 5.5 × 10³ m^–1).