Selective Recognition Behavior of Arginine and Histidine Using an Anionic Luminescent Metal‐Organic Material Stabilized by Cationic Amine: Steady State and Time‐Resolved Luminescence Studies

A new Eu‐based metal‐organic material, [Eu(CAM) 2 (H 2 O)] 0.5H 2 Pip·H 2 O, [CAM = chelidamate and H 2 Pip = diprotonated piperazine], 1, was synthesized by hydrothermal technique. Structure elucidation of compound 1 was done by single‐crystal X‐ray diffraction. The connectivity between Eu 3+ ions and chelidamate ligands forms anionic dimeric metal‐organic structures stabilized by interdimer OH···O hydrogen bond interactions involving the free hydroxyl groups and carboxylate oxygen atoms. The OH···O hydrogen bonds connect each dimeric unit with four other dimeric units to form a supramolecular 2D structure with rhombus grid topology. The 2D anionic hydrogen‐bonded structures are further stabilized through NH···O hydrogen bond interactions by involving piperazinediium ion to form an overall 3D supramolecular assembly. pH‐dependent luminescence studies of compound 1 confirmed its stable nature in the pH range of 1–11. Luminescence turn‐off behaviors of compound 1 were observed in the presence of two amino acids, for example, L‐arginine (Arg) and L‐histidine (His), in water. Luminescence decay processes and lifetime values confirmed that the quenching of luminescence of compound 1 by arginine is due to both static and dynamic quenching, but in the case of histidine, the quenching is purely static in nature.