Graphene films are used to detect the presence and transition of spin crossover nanoparticle aggregates. Experiments performed far from the graphene neutrality point, combining impedance spectroscopy and Hall measurements, provide better insight into the mechanism for the change of impedance of the graphene layer in proximity with different states of the molecular structure. We observe that the change of spin state shifts the graphene Fermi level and its intrinsic resistance, with resulting positive insight into using this type of hybrid device for fast molecular electronics purposes.