Deactivating groups such as other nitro groups have an electron pair withdrawing effect which deactivates the reaction (creating difficulty in the formation of poly-nitro products) and directs the electrophilic nitronium ion to attack the aromatic meta position.
Deactivating groups such as other nitro groups have an electron pair. This electron pair is withdrawing effect. This effect deactivates the reaction. This effect directs the electrophilic nitronium ion. This is to attack the aromatic meta position.