Solution structures of luminescent chelates of europium(III) with 2,6-bis[N,N-bis(carboxymethyl)aminomethyl]-4-benzoylphenol

2,6-Bis[N,N-bis(carboxymethyl)aminomethyl]-4-benzoylphenol forms with europium(III) three structurally different luminescent chelates in aqueous sample solutions. Only the chelate with a dimeric structure, where two Eu(III) cations are encapsulated into the chelating cage consisting of two deprotonated phenolic hydroxyl groups and four 2,2'-(methylenenitrilo)bis(acetic acid) moieties having strong interactions with the deprotonated hydroxyl groups, is capable of initiating the sensitized D-5(0) --> F-7(j) transitions of Eu(III) with an exceptionally long lifetime of 0.97 ms.