Abstract We consider the following Schrödinger–Poisson system {−Δu+V(x)u+λϕ(x)u=ulogu2,x∈ℝ3,(0.1)−Δϕ=u2,lim|x|→+∞ϕ(x)=0, where λ∈R is a parameter, V∈C(R3,R+) is a coercive potential. We prove that, if V(x)∼(log|x|)12 at infinity, then the energy functional I λ associated with (0.1) fails to be C 1 , and there is λ0