Deep Molecular Orbital Driven High-Temperature Hydrogen Tautomerization Switching

Abstract

Hydrogen tautomerization molecular switches, a promising class of molecular components for the construction of complex nanocircuits, have been extensively studied using low-temperature scanning tunneling microscopy. However, these molecules are generally only reliably controllable in cryogenic environments, obstructing their utility in real devices. Here, we use dispersion-inclusive density functional theory and systematically investigate the adsorption and tautomerization behaviors of porphycene on six transition-metal surfaces. Among these surfaces, we found that hydrogen tautomerization on the Pt(110) surface corresponds to the largest switching barrier, allowing a controllable transition at high temperature. The switching behavior is closely related to the exceptional degree of charge transfer in the HOMO−2 orbital, illustrating the important role of deep orbital−surface interactions in porphycene molecular switching. Our work provides an in-depth understanding of the porphycene tautomerization mechanism and highlights new research avenues toward the practical application of molecular switches.

One molecule, two states: Single molecular switch on metallic electrodes

“…Tautomerization is another type of molecular switch 30,31,134–138 . Since the tautomerization process only involves the intramolecular hydrogen atom transfer, it could avoid dramatic structural change during switching.…”

“…The small barrier makes the tautomerization switching sensitive to small thermal disturbances and can only be controlled at low temperatures. Previous experimental observations have demonstrated that the tautomerization temperature is closely related to the strength of the surface–molecule interaction 31,37,138,147 . Therefore, changing the metal surface can adjust the interaction and thereby improving the switching barrier.…”

“…Therefore, changing the metal surface can adjust the interaction and thereby improving the switching barrier. On the (110) surface, Liu's group 138 studied the tautomerization behavior of porphycene on the six transition metal surfaces to find the appropriate switching temperature. The switching temperature can be estimated by DFT calculation.…”

“…Tautomerization is another type of molecular switch. 30,31,[134][135][136][137][138] Since the tautomerization process only involves the intramolecular hydrogen atom transfer, it could avoid dramatic structural change during switching. In these cases, the central macrocycle of the molecule performs as a protective environment for the intramolecular hydrogen transfer, and thus the carefully designed molecular function will not be easily perturbed.…”

“…Most of the studies on tautomerization experiments were carried out at low temperature STM due to the low tautomerization switching barrier. 138,149 The small barrier makes the tautomerization switching sensitive to small thermal disturbances and can only be controlled at low temperatures. Previous experimental observations have demonstrated that the tautomerization temperature is closely related to the strength of the surface-molecule interaction.…”