Novel chelating agents and highly luminescent and stable chelates and their use

A chelating agent comprising

• a chromophoric moiety comprising two or more aromatic units, wherein at least one of the aromatic units is a trialkoxyphenylpyridyl group, where the alkoxy groups are the same or different, and the pyridyl groups are i) tethered directly to each other to form a bipyridyl or terpyridyl group, respectively, or ii) tethered to each other via N-containing hydrocarbon chains,
• a chelating part comprising at least two carboxylic acid or phosphonic acid groups, or esters or salts of said acids, attached to an aromatic unit of the chromophoric moiety, either directly or via an N-containing hydrocarbon chain, and
• optionally a reactive group A, tethered to the chromophoric moiety or to the chelating part either directly or via a linker x, said reactive group A enabling binding either to a biomolecule or to a functional group on a solid phase.