Abstract
Molecular rotors with controllable functions are promising for molecular machines and electronic devices. Especially, fast rotation in molecular rotor enables switchable molecular conformations and charge transport states for electronic applications. However, the key to molecular rotor-based electronic devices comes down to a trade-off between fast rotational speed and thermal stability. Fast rotation in molecular rotor requires a small energy barrier height, which disables its controllability under thermal excitation at room temperature. To overcome this trade-off dilemma, we design molecular rotors with co-axial polar rotating groups to achieve wide-range mechanically controllable rotational speed. The interplay between polar rotating groups and directional mechanical load enables a “stop-go” system with a wide-range rotational energy barrier. We show through density functional calculations that directional mechanical load can modulate the rotational speed of designed molecular rotors. At a temperature of 300 K, these molecular rotors operate at low rotational speed in native state and accelerates tremendously (up to 1019) under mechanical load.
Highlights
Artificial molecular rotors are attracting increasing interests for their potential applications in molecular machines and nanomechanical electronic devices[1]
According to transition state theory, there is a trade-off between rotational speed k and thermal stability: k / kBT eÀΔGz=kBT ; (1)
Tremendous wide-range rotational speed is achieved under modulation of directional mechanical load
Summary
Artificial molecular rotors are attracting increasing interests for their potential applications in molecular machines and nanomechanical electronic devices[1]. For application in molecular devices, molecular rotors require both fast rotational speed and thermal stability. Fast rotational speed and thermal stability cannot exist at the same time This comes down to a trade-off dilemma in designing molecular rotors: accelerating rotational speed leads to reducing of thermal stability, and vice versa[2,3,21,22]. For application in modern electronic devices, molecular rotors require even larger tuning range: operations require rotational speed at Gigahertz (109 Hz) while thermal stability requires rotation ceased as long as possible, e.g., one day (10−6 Hz). To achieve wide-range rotational speed at room temperature, we design a series of anthracene-based molecular rotors with rotational energy barrier ultra-sensitive to directional pressure. Through substituting different polar rotors, modulation of different ranges of rotational speed can be achieved
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