Room-temperature Single-molecule Conductance Switch via Confined Coordination-induced Spin-State Manipulation.

The emergence of molecular spintronics offers a unique chance for the design of molecular devices with different spin-states, and the control of spin-state becomes essential for molecular spin switches. However, the intrinsic spin switching from low- to high-spin state is a temperature-dependent process with a small energy barrier where low temperature is required to maintain the low-spin state. Thus, the room-temperature operation of single-molecule devices has not yet been achieved. Herein, we present a reversible single-molecule conductance switch by manipulating the spin states of the molecule at room temperature using the scanning tunneling microscope break-junction (STM-BJ) technique. The manipulation of the spin states between S = 0 and S = 1 is achieved by complexing or decomplexing the pyridine derivative molecule with a square planar nickel(II) porphyrin. The bias-dependent conductance evolution proves that the strong electric field between the nanoelectrodes plays a crucial role in the coordination reaction. The density functional theory (DFT) calculations further reveal that the conductance changes come from the geometric changes of the porphyrin ring and spin-state switching of the Ni(II) ion. Our work provides a new avenue to investigate room-temperature spin-related sensors and molecular spintronics