Organophosphate (OP) nerve agents and pesticides are potent inhibitors of acetylcholinesterase (AChE). Though oxime nucleophiles can reactivate an AChE-phosphyl adduct, the adduct can undergo a reaction called aging, leading to an aged-AChE adduct. The invention provides compounds and methods that can be used to reactivate an aged-AChE adduct. Such compounds and methods are useful to counteract organophosphorus poisoning.