Molecular memory near room temperature in an iron polyanionic complex

Abstract

Single molecules are the smallest processable units for information storage and sensing. However, molecular phenomena are typically limited to very low temperatures. Thermal energy is able to depopulate (erase) the excited state back to the ground state. Spin-crossover (SCO) molecules are an exception to this rule, showing memory effect above room temperature, but only when the electronic switchability is associated with a bulk phase transition. This synergy has its origin in the cooperativity among SCO molecules in the crystal, disappearing in diluted samples. We have found a surprising exception to this model: a polyanionic iron complex capable of showing memory effect even upon dilution. Our results demonstrate that molecular species can exhibit thermal hysteresis if intramolecular interactions are able to slow down the relaxation processes at the single-molecule level. Our findings open unprecedented opportunities for single-molecule memories at (and above) room temperature.