  Two new photo-switchable terphenylthiazoles molecules are synthesized and
self-assembled as monolayers on Au and on ferromagnetic Co electrodes. The
electron transport properties probed by conductive atomic force microscopy in
ultra-high vacuum reveal a conductance of the light-induced closed (c) form
larger than for the open (o) form. We report an unprecedented conductance ratio
up to 380 between the closed and open forms on Co for the molecule with the
anchoring group (thiol) on the side of the two N atoms of the thiazole unit.
This result is rationalized by Density Functional Theory (DFT) calculations
coupled to the Non-Equilibrium Green's function (NEGF) formalism. These
calculations show that the high conductance in the closed form is due to a
strong electronic coupling between the terphenylthiazole molecules and the Co
electrode that manifests by a resonant transmission peak at the Fermi energy of
the Co electrode with a large broadening. This behavior is not observed for the
same molecules self-assembled on gold electrodes. These high conductance ratios
make these Co-based molecular junctions attractive candidates to develop and
study switchable molecular spintronic devices.
