Bản ghi email: {1-[1-(2-Hy­droxy­phen­yl)ethyl­idene]-2-(pyridin-2-yl-κN)hydrazine-κ(2) N′,O}{1-[1-(2-oxidophen­yl)ethyl­idene]-2-(pyridin-2-yl-κN)hydrazine-κ(2) N′,O}nickelate(II) nitrate hemihydrate