Working Mechanism And Computational Design Of Faster Imine-Based Light-Driven Molecular Rotary Motor

Molecular motors are the smallest man-made machines so far,which can continuously achieve full 360° unidirectional rotations by absorbing external energies.Molecular motors are very common in the field of life science,for example,ATPase is a type of molecular motors that can convert chemical energies into mechanical energies.At present,Light-driven molecular motors are the main products that humans can synthesize.Light-driven molecular motors work by converting absorbed photonic energies to mechanical energies.The rotation process of light-driven molecular motor mainly consists of photoisomerizations and thermal isomerizations.Photoisomerizations are photon absorbing process that molecular motor can perform work to surroundings.However,thermal isomerizations are the rate-determining process that affect the rotation rate of molecular motors,thus named as rate-limiting thermal isomerizations.Increasing rotational frequencies of molecular motors is a major challenge for their practical applications.Theoretical calculations of molecular motors using quantum chemical methods can help people understand their rotation mechanisms more completely,as well as help us design faster rotating molecular motors.Thus,in this work,two imines light-driven molecular motors have been studied using ω B97X-D long-range-corrected hybrid density functionals in combination with the double-ζ SVP basis set,and two rotation mechanisms of these two molecular motors thus have been proposed.Imines light-driven molecular motor with flexible stator,named as molecular motor 5,has been known as a four-step rotation mechanism,and imines light-driven molecular motor with rigid stator,named as molecular motor 6,has been known as a two-step rotation mechanism.However,our calculations show that molecular motor 5 performs a four-step cycling motion while the molecular motor 6 performs a three-step cycling motion.A new intermediate state structure of the thermal process of molecular motor 6 has been discovered in our calculations,thus this thermal process performs as a 2-step mechanism.Meanwhile,a theoretical design of faster rotating light-driven molecular motor has been proposed under the calculations of molecular motor 5,and this computing product significantly reduces the free-energy barriers of the rate-limiting thermal steps.In order to extract and process calculated data of output files,a series of algorithm designs have been developed in this paper.These algorithm designs include spatial transformations of atomic coordinates,such as translation,rotation and alignment,format arrangement of Hessian matrixes and calculations about the rotational inertia and torsion of molecules.The data processed by the above algorithms will be used to generate new input files for next calculations or analyze the rotation mechanism of molecular motors directly.