A polynuclear complex having two or more metal atoms and/or metal ions per one ligand of the general formula (I):
(wherein, Q1 and Q2 represent each independently a divalent heterocyclic group optionally having a substituent. R1 and R2 represent each independently a direct bond or divalent hydrocarbon group, X represents a nitrogen atom or phosphorus atom, and R3 represents a monovalent organic group containing an atom selected from a nitrogen atom, oxygen atom, phosphorus atom and sulfur atom, or a hydrogen atom or hydrocarbon group