A novel
coordination complex formed by dinuclear
metal complexation is provided. The complex is a dinuclear
metal complex of a compound, wherein the compound comprises a conjugation ring
system substituted with: a) an
electron donating group selected from —OH, —SH and —NH2; b) an indicating group selected from a
chromogenic group, a fluorescent group and an electrochemical group; and c) two binding auxiliary groups, in combination with the
electron donating group each of which being coordinated with the
metal to provide an anion bonding site, wherein as the complex binds to a anion, the coordination of the
electron donating group with the metal is weakened and electron donation of the electron donating group to the conjugation ring
system is reinforced such that the reinforced electron donation by the electron donating group is transferred through the conjugation ring
system to the indicating group to produce an indicating
signal concomitant with the change of its
electronic density. The
coordination complex shows high sensitivity and
high selectivity for
pyrophosphate over other anions in an aqueous
solvent over a wide
pH range. Therefore, the complex is useful for
pyrophosphate assay as a
pyrophosphate sensor.