  We consider a scalar-tensor model of dark energy with kinetic and Gauss
Bonnet couplings. We study the conditions for the existence of quintessential
and phantom power-law expansion, and also analyze these conditions in absence
of potential (closely related to string theory). A mechanism to avoid the Big
Rip singularity in various asymptotic limits of the model has been studied. It
was found that the kinetic and Gauss-Bonnet couplings might prevent the Big Rip
singularity in a phantom scenario. The autonomous system for the model has been
used to study the stability properties of the power-law solution, and the
centre manifold analysis was used to treat zero eigenvalues.
