An all Cartesian reaction surface Hamiltonian for the title reaction is calculated using density functional theory. Two reaction coordinates are chosen to model the motion of the proton in the plane of the pyridine and imidazole rings. The remaining degrees of freedom of the molecular scaffold are described by orthogonal normal modes. The reorganization energy of the latter is determined and the modes which are most strongly coupled to the proton transfer are analyzed. Based on this multidimensional potential energy surface the applicability of different schemes for ultrafast laser controlled isomerization is discussed.