[{"from": "human", "value": "Create a molecule with the structure as the one described. The molecule is a nickel cation in which the nickel carries a double positive charge. It has a role as a cofactor. It is a divalent metal cation, a metal cation allergen, a nickel cation and a monoatomic dication."}, {"from": "gpt", "value": "[Ni+2]"}]