  We investigate the spectral evolution in different metal phthalocyanine
molecules on NbSe$_2$ surface using scanning tunnelling microscopy (STM) as a
function of the coupling with the substrate. For manganese phthalocyanine
(MnPc), we demonstrate a smooth spectral crossover from Yu-Shiba-Rusinov (YSR)
bound states to spin-flip excitations. This has not been observed previously
and it is in contrast to simple theoretical expectations. We corroborate the
experimental findings using numerical renormalization group calculations. Our
results provide fundamental new insight on the behavior of atomic scale
magnetic/SC hybrid systems, which is important for e.g. engineered topological
superconductors and spin logic devices.
