Conjugates of 1,3-bis(1,4,7-triazacyclonon-1-yl)-2-hydroxypropanes with a variety of conjugating members are used in the formation of dinuclear metal complexes which bind to phosphate esters. By virtue of their conjugated forms, the complexes are incorporated into chromatographic media, affinity binding reagents, and dyes, which make the complexes useful in a wide range of assays, separations, and purifications. In addition, dinuclear metal complexes of 1,3-bis(1,4,7-triazacyclonon-1-yl)-2-hydroxypropanes that are not so conjugated are used in the detection of phosphate esters of biological species by either MALDI-TOF mass spectrometry or by dye displacement.