An unexpected dual-response pH probe based on acridine.

A new pH fluorescent probe 2,8-bis(acridin-9-ylethynyl)-6 H ,12 H -5,11-methanodibenzo[ b , f ][1,5]diazocine (TBN), which has two acridine moieties attached to Tröger's base, is a useful fluorescent probe for monitoring extreme acidic and alkaline pH. TBN displays an excellent pH dependent behavior and responds linearly to extreme conditions in the pH ranges of 1.4-3.4 and 12.5-15.0. TBN can represent a novel type of fluorescent probe with perfect emission properties in extreme acidic and alkaline conditions by utilizing only one functional group.