Provided is an organic ligand capable of providing a complex that has a three-dimensional network structure due to rare-earth element ions. Also provided is a coordination polymer which includes this organic ligand, has a new function, and contains rare-earth element ions. Additionally, a process for producing the coordination polymer and a use of the coordination polymer are provided. In particular, provided is a coordination polymer having repeating units of formula (10): ##STR00001##
wherein each of the variable groups is as defined in the specification.

Provided is an organic ligand capable of providing a complex that has a three-dimensional network structure due to rare-earth element ions. Also provided is a coordination polymer which includes this organic ligand, has a new function, and contains rare-earth element ions. Additionally, a process for producing the coordination polymer and a use of the coordination polymer are provided. In particular, provided is a coordination polymer having repeating units of formula (10):

##STR00001##

wherein each of the variable groups is as defined in the specification.

The embodiments provide a fluorescent rare earth complex having strong emission intensity and excellent durability, and also provide a security medium using the complex. The rare earth complex according to the embodiment comprises a rare earth ion, a diphosphine dioxide ligand and a -diketone ligand wherein two phosphorus atoms contained in the diphosphine dioxide ligand individually have substituents different from each other.

A compound according to Formula (I), or a pharmaceutically acceptable salt thereof: ##STR00001##
wherein R.sup.1 and R.sup.2 are each independently selected from optionally substituted C.sub.1-6-alkyl and optionally substituted aryl; R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are each independently selected from the group consisting of H, halo, optionally substituted C.sub.1-6-alkyl, and optionally substituted C.sub.1-6 alkoxy; and R.sup.7 is a phosphorus containing moiety, wherein a phosphorus atom is bonded to Au.

A rare earth complex is represented by general formula (1).

M.sup.3+.Math.(HC).sub.n.Math.(L.sup.1).sub.m.sub.1.Math.(L.sup.2).sub.m.sub.2.Math.(X.sup.L).sub.3-n(1) [In the formula, HC represents a quinolinonato ligand or coumarinato ligand, L.sup.1 represents, for example, a nitrogen-containing ligand, L.sup.2 represents, for example, water, X.sup.L represents, for example, a halide ion, M.sup.3+ represents a trivalent rare earth metal ion, n represents 1, 2 or 3, m.sup.1 represents 0, 1 or 2, and m.sup.2 represents 0 to 3.]