The dispersive behavior of the magnitude and phase of chi(3)(-3 omega : omega,omega,omega,) of sublimated baron subphthalocyanine (SubPc) thin films has been investigated via third harmonic generation (THG) spectroscopy in the range 950-2000 nm. chi(3) values, three times bigger than those obtained for phthalocyanines in the same frequency range, have been measured. A four-level model, including the ground state and three excited states associated to bands observed in the linear absorption spectrum, has been successfully used to explain the nonlinear behavior of these compounds.