The claimed invention provides a novel compound not having been studied before, that is, a diene carboxylate anion that contains a specific structure, and a salt thereof. The claimed invention further provides a diene carboxylate anion and a salt thereof, especially a metal salt thereof, which are easily soluble in general organic solvents, reactive diluents, and resins, may be in a liquid state at normal temperature depending on the structure, and have high polymerizability. Polymerization/curing of these produces a resin to which many ionic bonds and a metal are introduced, providing various properties such as hardness, scratch resistance, anti-fingerprint property, gas-barrier property, water vapor barrier property, oxygen absorption property, ultraviolet protection, infrared protection, color development and coloring, high refractive index, adhesion, various catalytic abilities, fluorescence ability and light-emitting ability, optical amplification, dispersibility, and antistatic properties. In addition, the anion and the salt can be used for raw materials for functional fine particles and for metal nanoparticle composites, and also for MOD materials. The claimed invention also provides an advantageous method for producing the diene carboxylate anion and the salt thereof.