We present a fully quantum-mechanical approach for the design of molecular energy nanotransmitters. To illustrate the implementation of this approach, a reduced-dimensionality model of the ethane molecule (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ), in which the two methyl (CH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) groups are considered as coupled rigid rotors, is chosen as a tractable prototype. For relevant initial conditions, the multiconfigurational time-dependent Hartree (MCTDH) method is employed to simulate the quantum dynamics of rotational energy transmission between the two methyl groups. Our approach can be extendable to more complex nanomachines.