  Herein we develop a simple first-principles methodology to determine the
modulation that vibrations exert on spin energy levels, a key for the rational
design of high-temperature molecular spin qubits and single-molecule magnets.
This methodology is demonstrated by applying it to [Cu(mnt)$_2$]$^{2-}$
(mnt$^{2-}$ = 1,2-dicyanoethylene-1,2-dithiolate), a highly coherent complex,
using DFT to calculate the normal vibrational modes and wave-function based
theory calculations to estimate the spin energy level structure. By
theoretically identifying the most relevant vibrational modes, we are able to
offer general strategies to chemically design more resilient magnetic
molecules, where the qubit energy is not coupled to local vibrations.
