Gaussian-External Methodology Predicted Crystal Structures, Molecular Energetics, and Potential Energy Surface of the Crystalline Molecular Compass

Abstract

Nanoscience, Nanotechnology, and Molecular machines have triggered the scientists of wide-ranging disciplines alike for decades now, offered the most innovative technologies to maneuver the nanoscale devices molecule by molecule. In this arena of the nano-metric world, the strategical laboratorial syntheses & computational designations of the prototype molecules/nanomaterials and the most probable techniques for their effective functionalization always stand as mandatory credentials. Among various types of functionalizing nanomaterials, the topologically closed Si and -(Si-O)x- based dipolar crystalline macrocyclic molecular compounds exhibiting macroscopic compass/gyroscope like functions at ambient temperatures have attracted the greatest admirations. In this outlook, the research works presented herewith by employing a Gaussian-external methodology for the quantum mechanical characterizations of the crystal structures, computations of the molecular energetics, and derivations of the rotational potential energy surface (PES) of the experimentally synthesized difluoro- /dichloro- phenylene encapsulated amphidynamic/non-amphidynamic crystalline ROT-2F/ROT-2Cl siloxaalkane macrocages can be taken as a stepping stone. Under the standardized interface of Gaussian, we ran SCC-DFTB scheme via the user's script as an external program, and accessed the PES scanning techniques of the former plus the "Dispersion Energy correction" features of the latter computationally. The results reported herein are mainly found to (a) validate the X-ray produced degenerate and non-degenerate crystal structures, (b) justify the experimentally observed structural deformations of the static siloxaalkane spokes, (c) quantize the free-volume units available around the rotator, (d) disclose the energy barrier Ea to be overcome by the rotator while exhibiting 1p-flipping motion, (e) foresee the structural requisites to be adopted for designing functional crystalline free-rotors, etc. It is believed that present theoretical study enlightens us about the most essential structural and dynamical features of the gyroscopic nanostructures & molecular compasses quantitatively.