The realization of single molecular electronics is considered the next frontier to addressing and sustaining the storage needs of the future. In order to realize a single molecular device working at 300 K, two conditions must be satisfied: firstly, there must be no molecular diffusion, i.e., robust bonding between molecules and the contacting electrode, and secondly, stable electronic interface states. In this study, using a combination of 7-K and 300-K ultrahigh vacuum scanning tunneling microscopy/spectroscopy experiments and theoretical ab-initio calculations, we investigated the adsorption of π-conjugated metal-free phthalocyanine (Pc) single molecules onto an Fe(001) whisker single crystal along with the resulting electronic interface structures. The Pc/Fe(001) system was found to prevent molecular diffusion even at 300 K, due to strong adsorption as well as the presence of a larger diffusion barrier than that of the Pc/Ag(001) system, in which molecules are known to diffuse at 300 K. The origin of such a robust bonding was studied by recovering the sample local density of states (LDOS) with the normalized (dI/dV)/T curves, which LDOS peaks are successfully explained by theoretical calculations.