  We present a novel energy-based localization procedure able to localize
molecular orbitals into specific spatial regions. The method is applied to
several cases including both conjugated and non-conjugated systems. The
obtained localized molecular orbitals are used in a multiscale framework based
on the multilevel Hartree-Fock approach. An almost perfect agreement with
reference values is achieved for both ground state properties, such as dipole
moments, and local excitation energies calculated at the coupled cluster level.
The proposed approach is useful to extend the application range of high level
electron correlation methods. In fact, the reduced number of molecular orbitals
can lead to a large reduction in the computational cost of correlated
calculations.
