A new quantum time-dependent treatment has been employed to model the photoexcitation of LiH2+ by looking at the process both in a constrained configuration and in the full three-dimensional space. The study has been carried out by monitoring at the end of the process the fragmentation probabilities, the final vibrational distributions of the molecular fragments, and the angular evolution of the wave functions of the complex on the excited electronic surface. The comparison between different initial conditions is able to shed light on the microscopic mechanism of the energy redistribution, with particular reference to the role of the angular coordinate that turns out to provide efficient energy channeling during the evolution. The possibility of extending the method to larger systems is briefly discussed.