1 research outputs found
New Class of Molecular Conductance Switches Based on the [1,3]-Silyl Migration from Silanes to Silenes
On
the basis of first-principles density functional theory calculations,
we propose a new molecular photoswitch which exploits a photochemical
[1,3]-silylÂ(germyl) shift leading from a silane to a silene (a Siî—»C
double bonded compound). The silanes investigated herein act as the
OFF state, with tetrahedral saturated silicon atoms disrupting the
conjugation through the molecules. The silenes, on the other hand,
have conjugated paths spanning over the complete molecules and thus
act as the ON state. We calculate ON/OFF conductance ratios in the
range of 10–50 at a voltage of +1 V. In the low bias regime,
the ON/OFF ratio increases to a range of 200–1150. The reverse
reaction could be triggered thermally or photolytically, with the
silene being slightly higher in relative energy than the silane. The
calculated activation barriers for the thermal back-rearrangement
of the migrating group can be tuned and are in the range 108–171
kJ/mol for the switches examined herein. The first-principles calculations
together with a simple one-level model show that the high ON/OFF ratio
in the molecule assembled in a solid state device is due to changes
in the energy position of the frontier molecular orbitals compared
to the Fermi energy of the electrodes, in combination with an increased
effective coupling between the molecule and the electrodes for the
ON state