  The interplay of electron-electron and electron-phonon interactions is
studied analytically in the Kondo regime. A Holstein electron-phonon coupling
is shown to produce a weakening of the gate voltage dependence of the Kondo
temperature and may explain the observed anomalies in some of these devices. A
molecular center-of-mass mode opens a new channel for charge and spin
fluctuations and in the antiadabatic limit the latter are described by an
asymmetric two-channel Kondo model. Below the Kondo temperature the system
develops a dynamical Jahn-Teller distortion and a low energy peak emerges in
the phonon spectral density that could be observed in Raman microscopy
experiments.
